Road Runoff Harvesting in the
Drylands of Sub-Saharan Africa:
Its Potential for Assisting Smallholder Farmers in
Coping with Water Scarcity and Climate Change,
Based on Case Studies in Eastern Province, Kenya
BEN KUBBINGA
FREE UNIVERSITY / VRIJE UNIVERSITEIT, AMSTERDAM
FACULTY OF EARTH AND LIFE SCIENCES
A THESIS SUBMITTED TO THE INSTITUTE OF ENVIRONMENTAL SCIENCES IN
PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER IN
SCIENCE IN ENVIRONMENT AND RESOURCE MANAGEMENT (SPECIALISATION
BIODVERSITY AND ECOCYSTEM SERVICES)
Supervisors:
Dr Will Critchley, Center for International Cooperation (CIS-VU), Amsterdam
Dr Jetske Bouma, Institute for Environmental Studies (IVM-VU), Amsterdam
Dr Maimbo Malesu, World Agroforestry Centre (ICRAF), Nairobi
Alex Oduor, World Agroforestry Centre (ICRAF), Nairobi
I
Acknowledgements
This thesis is the product of fieldwork carried out in Kenya and a literature study in The Netherlands.
Many people have helped me in making these activities possible.
First of all, I would like to thank my supervisors for their guidance and patience. I am grateful to Dr Will
Critchley for his suggestion to focus my thesis on the topic of road runoff harvesting, as well as for his
continuous positive feedback despite the many delays in preparing this thesis. I would like to thank Dr
Jetske Bouma for her critical and constructive comments when I presented the first results of my
fieldwork and for her further support during the writing. My fieldwork would not have been possible
without the kind hospitality and expertise offered by Dr Maimbo Malesu and Alex Oduor, who have
dedicated much of their time in visiting the different road runoff harvesting sites with me.
I am grateful for the warm welcome and support provided by Ms Hellen Ochieng and Ms Rose
Onyango during my stay at ICRAF. I would also like to thank the staff of the ICRAF library for their kind
help. I further appreciate Dr Stephen Ngigi’s help in acquiring one of his books (Ngigi, 2003a) and his
PhD thesis.
During my field visits I have been accompanied by Ms Rose Mueni. I am very much indebted to her for
her nice company and her willingness to translate from Kiswahili or Kikamba to English, and vice versa
– which was most useful both during interviews and in our free time. I am particularly obliged to all the
farmers who have been so kind to host me from a couple of hours to a few days. These farmer
innovators are: Mr Muindu Musyoka, Mr Mwema Maswili, Mr Samuel Mweu Maingi, a neighbour of Mr
Samuel Maingi, Mr David Kyula and Mr Sammy. Though they are not part of the case studies, I would
also like to give thanks to Mr Daniel Kyalo and Mr Patrick Mwendwa, whose farms I have visited
during my stay at Mr Musyoka’s farm in Mwingi District.
At the Kenya Rainwater Association, I have been welcomed by Ms Katie Allan. I greatly appreciate her
assistance in providing information on the activities of KRA and her help in giving me access to the
KRA library. I would also like to thank Ms Elizabeth Khaka – the ‘grandmother of water harvesting in
Africa’ – for her availability to discuss the activities of UNEP in the field of water harvesting. On the
same ‘family’ note, I was pleased to meet Mr Erik Nissen-Petersen – the ‘grandfather of water
harvesting in Africa’ – who kindly provided me with a hard copy of his book ‘Water from roads’
(Nissen-Petersen, 2006).
Furthermore, I would like to warmly thank my friends Adriaan Tas, Angela Kronenburg and their
children for hosting me during my stay in Nairobi.
Last but not least, I am very thankful to Sanne Jansen, Peter de Lange and Alba Martinez Salas for
proofreading parts of this thesis and for their useful suggestions.
I
Preface
This thesis is the final part of the MSc programme “Environment and Resource Management”, ERM in
short, which I followed during the period 2010-2011. This programme is provided by the Institute for
Environmental Studies (IVM) of the Vrije Universiteit (VU) in Amsterdam. I made the decision to carry
out this short research project during the one-month course on Sustainable Land Management (SLM),
provided by Dr. Will Critchley of the Centre for International Cooperation (CIS). The SLM course has
been one of the most inspiring courses of the ERM programme, in particular because of the many
practical real-life examples of SLM technologies and approaches that were given. I have been given
the chance to go to Kenya for fieldwork, under the local supervision of Dr Maimbo Malesu and Alex
Oduor, two experts in rainwater harvesting at the World Agroforestry Centre based in Nairobi. This
chance I have taken with both hands. My fieldwork in the countryside of Eastern Kenya has allowed
me to get to know some of the most humble, hospitable and kind people I know. Though the outcomes
of this study are limited in scope, I hope they can contribute to the further promotion of the various
forms of road runoff harvesting amongst smallholder farmers in Kenya and the rest of sub-Saharan
Africa.
Summary
Water scarcity is a major challenge for smallholder farmers in the drylands of sub-Saharan Africa,
where agriculture is predominantly rainfed. Collecting runoff from road surfaces and culverts may help
some of these farmers in coping with the unreliable and erratic rainfall. Road runoff harvesting (RRH),
as this technology is called, is already practiced by several farmers for instance in Kenya, Tanzania
and Uganda. The objective of this thesis was twofold: 1) to evaluate the performance of farms that use
RRH, and 2) to assess the potential for up-scaling RRH in the rest of sub-Saharan Africa. Two case
studies in Kenya were selected prior to this study, and four other sites were visited as well during the
fieldwork. The WOCAT Questionnaire on SLM Technologies was used as a basic framework for
collecting data on the performance. The data were further analysed using the TEES-test, which
focuses on the Technical performance, Economic viability, Environmental friendliness and Social
acceptance of a technology. The outcomes suggest that the RRH systems perform well – farmers are
overall positive about the impacts of their RRH system. Small technical improvements could be made
in all cases. The establishment costs are a major economic constraint, yet the benefits seem to
outweigh these and other (social) costs. Negative environmental effects have not been observed. The
RRH systems of the two case studies are based on both local knowledge and expertise from
development agents. Assessment of the potential for up-scaling RRH was done with data on the size
of drylands of each country in sub-Saharan Africa, combined with road density data per country and
informed estimates of the road surface and number of culverts per kilometre of road; population
density levels per dryland area (arid, semi-arid and dry sub-humid) were used as a proxy to calculate
the road density for each area. The results show a large potential for RRH: some 2.2 million
households (including both smallholder farmers and pastoralists) could potentially benefit from an
estimated 0.5 cubic kilometre of road runoff, either through runoff farming or by storing the runoff for
later use (for livestock or supplemental irrigation of crops). The findings are in line with the sporadic
yet promising information about RRH technologies in current (and often grey) literature. This study
highlights the importance of further research on the (technical, economic, environmental and social)
costs and benefits of RRH systems, involving more farms as well as a combination of success stories
and failures. Detailed GIS-mapping of regional and local opportunities for RRH would be very helpful
to estimate the real potential of this technology. Based on the present assessment, it is recommended
that national and local administrations, who deal with infrastructure, agriculture, environment or water,
as well as development agents, consider the incorporation of RRH into their policies, programmes and
activities.
II
Contents
Acknowledgements .............................................................................................................. I
Preface ................................................................................................................................. II
Summary .............................................................................................................................. II
Glossary ............................................................................................................................... 1
List of Figures...................................................................................................................... 2
List of Tables ....................................................................................................................... 3
List of Boxes ........................................................................................................................ 3
Acronyms and Abbreviations ............................................................................................. 4
1.
Introduction .................................................................................................................. 5
1.1 Problem analysis........................................................................................................ 5
1.2 Research questions ................................................................................................... 7
1.3 Thesis structure ......................................................................................................... 7
2.
Road runoff harvesting in sub-Saharan Africa........................................................... 8
2.1 The concept of road runoff harvesting ........................................................................ 8
2.2 Runoff harvesting with roadside drain .......................................................................10
2.3 Runoff harvesting through a culvert...........................................................................11
2.4 Benefits of road runoff harvesting for smallholder farmers ........................................13
2.5 Upstream-downstream impacts of road runoff harvesting .........................................14
2.6 Adoption by other farmers .........................................................................................15
2.7 Impacts of up-scaling ................................................................................................17
3.
Methods .......................................................................................................................18
3.1 Analysis framework for case studies .........................................................................18
3.2 Selection of case studies ..........................................................................................20
3.3 Study area ................................................................................................................21
3.4 Fieldwork and interviews ...........................................................................................21
3.5 Methodology for determining the potential for up-scaling road runoff harvesting .......22
4.
Results .........................................................................................................................27
4.1 Case study 1: Muindu Musyoka ................................................................................27
4.2 Case study 2: Mwema Maswili ..................................................................................34
4.3 Four other sites in Machakos District ........................................................................40
4.4 Suitable roads and culverts in sub-Saharan Africa ....................................................44
III
5.
Analysis .......................................................................................................................48
5.1 Technical performance..............................................................................................48
5.2 Economic viability .....................................................................................................50
5.3 Environmental friendliness ........................................................................................51
5.4 Social acceptance .....................................................................................................52
5.5 Factors that may influence the adoption of road runoff harvesting.............................53
5.6 Sensitivity analysis of the sub-Saharan Africa-wide assessment...............................55
6.
Discussion ...................................................................................................................57
6.1 Addressing the research questions ...........................................................................57
6.2 Performance of road runoff harvesting sites ..............................................................57
6.3 Potential for up-scaling road runoff harvesting in sub-Saharan Africa .......................58
6.4 Experience of using WOCAT and the TEES-test.......................................................59
6.5 Refining the sub-Saharan Africa-wide suitability assessment ....................................60
7.
Conclusions.................................................................................................................61
8.
Recommendations ......................................................................................................62
8.1 Further research .......................................................................................................62
8.2 Policy-making............................................................................................................62
8.3 Development and extension work .............................................................................63
References ..........................................................................................................................64
Annex I Categorisation of WOCAT data ...........................................................................68
IV
Glossary
adoption / uptake
the process of copying a technology by other farmer(s)
berkad
type sub-surface water tank used in Somalia
caag
external catchment system for harvesting water from ephemeral
streams (Kenya)
catchment
area used for collecting (road) runoff
cultivated lands
lands that are used for crop production or agroforestry (both
rainfed and irrigated)
cultivation area
area where runoff is applied for productive purposes
culvert
conduit (pipe or other structure) running underneath a road
constructed for drainage
drylands
arid, semi-arid and dry sub-humid areas
external catchment
catchment that lies outside the farm land (generally longer than 30
m)
fanya chini
terraces formed by channels along the contours of a hill that have
been created by throwing soil down (chini) hill (Kiswahili)
fanya juu
terraces formed by channels along the contours of a hill that have
been created by throwing soil down (juu) hill (Kiswahili)
hafir
natural depression/water pan in the landscape (Kenya)
hybrid knowledge
local/traditional and scientific knowledge combined
majaluba
retention basin (Tanzania)
microcatchment
catchment that lies within-field (generally less than 30 m long)
rangelands
lands used for nomadic and sedentary livestock raising
road runoff harvesting
the collection of runoff from roads and road sides for productive
purposes
shamba
farm field (Kiswahili)
T-basins
basins which trap runoff from footpaths and roads; crop are grown
on the interconnected (at the base) T-shaped bunds
technique
a single measure (e.g. digging a trench)
technology
a set of techniques plus the knowledge and skills to use these
techniques (e.g. water harvesting)
up-scaling
the process of increasing the rate of adoption by farmers
water harvesting
the collection of runoff for productive purposes
1
List of Figures
Figure 1. Projected reduction of plant growing periods in sub-Saharan Africa ....................... 5
Figure 2. The principle of rainwater harvesting ...................................................................... 8
Figure 3. Runoff harvesting with roadside drains: three basic forms .....................................10
Figure 4. Runoff harvesting through a culvert: two basic forms.............................................12
Figure 5. Picture of a gully formed at the outlet of a culvert ..................................................13
Figure 6. Map showing the location of the visited farms........................................................20
Figure 7. Methodology used to determine the suitability of roads for runoff harvesting .........22
Figure 8. Schematic depiction of runoff flows on Muindu Musyoka’s farm ............................27
Figure 9. Pictures of Muindu Musyoka showing how runoff is redirected to his farm.............28
Figure 10. Schematic overview of the terraces of Muindu Musyoka......................................29
Figure 11. Catchment and cultivation area of Muindu Musyoka highlighted on a
satellite image ....................................................................................................30
Figure 12. Muindu Musyoka showing dried maize in a calabash at his homestead...............33
Figure 13. Schematic overview of the Mwema Maswili’s farm ..............................................34
Figure 14. Roadside drain and fanya chini channel on the farm of Mwema Maswili ..............35
Figure 15. Pond of Mwema Maswili ......................................................................................36
Figure 16. Schematic overview of three of the four additional farms .....................................41
2
List of Tables
Table 1. Comparison of yields obtained with and without road runoff harvesting ................ 14
Table 2. Approaches and tools used to analyse each of the TEES-test criteria. ................. 18
Table 3. Methodology used to categorise data from the WOCAT Questionnaire on SLM
Technologies ........................................................................................................ 19
Table 4. Timing of field visits and type of interviews ........................................................... 21
Table 5. Characteristics of arid, semi-arid and dry sub-humid areas. ................................. 23
Table 6. Proportion of rangelands, cultivated lands, urban areas and other areas in the
drylands of the world. ........................................................................................... 24
Table 7. Summary of assumptions made to determine the potential for up-scaling road
runoff harvesting................................................................................................... 26
Table 8. Yields and sales of Muindu Musyoka during the period 1998-2011 ...................... 32
Table 9. Length of total road network in the drylands ......................................................... 45
Table 10. Estimates per country of number of culverts, potential runoff volumes and
number of households that could benefit from road runoff .................................... 46
Table 11. Estimates per country of road surface, potential cultivation area (in cultivated
lands), potential runoff volumes and number of households that could benefit
from road runoff .................................................................................................... 47
Table 12. Overview of rainwater harvesting elements on the six farms ................................ 48
Table 13. Description of the technical performance of each site. .......................................... 49
Table 14. Benefit-costs analysis of the road runoff harvesting systems of Musyoka and
Maswili ................................................................................................................. 50
Table 15. Environmental impacts and related Ecosystems Services of the studied road
runoff harvesting sites .......................................................................................... 52
Table 16. Adoption rates and reasons for successful or unsuccessful adoption ................... 53
Table 17. Overview of potential adoption factors derived from data gathered at the six
farms .................................................................................................................... 54
Table 18. Sensitivity of the outcomes of the sub-Saharan Africa-wide assessment .............. 56
Table 19. Structural adjustments that could make road runoff harvesting structures more
efficient. ................................................................................................................ 57
List of Boxes
Box 1. Ecosystem Services typical of drylands in Africa ........................................................ 6
Box 2. Methods for calculating the potential amount of road runoff and the cultivation area
size based on rainfall depth, runoff efficiency and crop water requirements ................ 9
Box 3. Road runoff harvesting in other parts of the world .....................................................16
3
Acronyms and Abbreviations
AMCOW
African Ministerial Conference on Water
C/CA ratio
Catchment/Cultivation Area ratio
E
efficiency factor
ETc
crop water requirements
FAO
Food and Agriculture Organization
GHA
Greater Horn of Africa
GHARP
Greater Horn of Africa Rainwater Partnership
GIS
Geographic Information Systems
GOK
Government of Kenya
ha
hectare (100 by 100 m = 10,000 m2 = 2.47105 acre)
ICRAF
World Agroforestry Centre
IPA
Issuing Paying Agent
IWRM
Integrated Water Resources Management
K
runoff coefficient
kc
‘crop’ factor
MEA
Millennium Ecosystem Assessment
O&M
Operation and Maintenance
Pd
design rainfall
PET
potential evapotranspiration
PFI
Promoting Farmer Innovation
QT
WOCAT’s Questionnaire on SLM Technologies
RRH
road runoff harvesting
SLM
Sustainable Land Management
SSA
sub-Saharan Africa
UNDP
United Nations Development Programme
UNEP
United Nations Environmental Programme
WOCAT
World Overview of Conservation Approaches and Technologies
WVI
World Vision International
4
1. Introduction
1.1 Problem analysis
Water scarcity is a major problem for smallholder
smallholde farmers in sub-Saharan
Saharan Africa, where agriculture is
predominantly rainfed (e.g. Falkenmark, 1989; Molden, 2007). At the country level, 40 to 70% of the rural
population depend for more than three-quarters
three
on on-farm
farm resources for their income (IFAD, 2011).
Particularly in Africa’s drylands, where some 325 people live (Murray et al.,, 1999),
1999) the unreliable and
erratic rainfall is a challenge.. Drylands comprise, in the context of this thesis, the arid, semi-arid and dry
sub-humid zones of sub-Saharan
Saharan Africa.
Africa Irrigation has not seen the same success as in South Asia under
the Green Revolution (IUCN, 2007) and is restricted to less than 5% of the agricultural produce in Africa
(FAO, 1992). Lack of basic infrastructure is one of reasons for the failure of irrigation schemes (Svendsen
(
et al., 2009). As this situation is likely to stay the same, solutions are required that help farmers to cope
with the limited availability of water for crop production.
In addition to the weather-related
related impacts on agricultural production, smallholder farmers also face other
uncertainties. As the majority of farmers are subsistence farmers
f
with an income below the poverty line,
line
food security is directly linked to local crop production (IFAD, 2010). As a result of the farmers’
vulnerability,, the economic situation (e.g. high market volatility) and social context (e.g. conflicts) of some
countries can greatly impinge on farm households (Ibid.).
Figure 1. Projected reduction of plant growing periods
period in sub-Saharan Africa
Two scenarios (left and right map) showing which areas will see a reduction in plant growing period of over 20% until
2050 (Thornton et al.,, 2006). The scenarios are based on two different models. The yellow areas (LGA) depict the
rangelands, the green areas
as (MRA) are used for rainfed mixed systems with crops and livestock. (For a definition of
rangelands and cultivated lands see Chapter 3.5)
5
Furthermore, agricultural lands are often degrading, i.e. losing their ability to support crop production, or
even degraded (FAO, 1993; Vlek et al., 2008). Ecosystem services that are characteristic for the drylands
(see Box 1) may thus be affected or lost (Millennium Ecosystem Assessment, 2005). Finally, climate
change is expected to worsen the conditions of rainfed agriculture in sub-Saharan Africa (Thornton et al.,
2006). In West Africa, rainfall will decrease and in East Africa it will likely increase, though here showers
will be shorter and more intensive. One of the consequences of the changing rainfall patterns will be
reduced plant growing periods (Ibid.). Figure 1 shows the areas that will see a reduction of over 20% in
plant growing period by the year 2050 based on two scenarios (left and right).
Box 1. Ecosystem Services typical of drylands in Africa
Supporting services
including soil formation, soil conservation, and nutrient cycling;
Regulating services
including water management, local climate regulation through surface
reflectance and evaporation, regulation of global climate through
carbon sequestration, and pollination and seed dispersal;
Provisioning services
including provisions derived from biological production (food and
fiber, woodfuel, biochemicals), and freshwater provisioning;
Cultural Services
including cultural identity, aesthetically pleasing landscapes, heritage
values, spiritual services, recreation and tourism.
Source: adapted from Safriel et al. (2002)
Despite these challenges, there is a clear potential for upgrading rainfed agriculture in sub-Saharan Africa
(Molden, 2007). Analysis of water flows has shown that much of the rain is lost to evaporation or as
runoff. Instead, simple technologies could change these ‘blue water’ flows into ‘green’ water flows, i.e.
water that is absorbed by plant roots and subsequently lost through evapotranspiration (Falkenmark,
1995; Rockström, 1999). In fact, a large gap exists between yields obtained in sub-Saharan African
(under rainfed conditions) and yields in Asia under similar conditions. Average yields are currently around
1 metric ton per hectare – with the available water, this could relatively easily be increased to 1.5-2.0
metric ton per hectare (Rockström and Falkenmark, 2000). Barron and Okwach (2004), for instance,
demonstrated that simple rainwater harvesting technologies (combined with soil fertility measures) can
boost agricultural production. Other studies have also highlighted the benefits from rainwater harvesting
in Africa’s drylands (e.g. Boers and Ben-Asher, 1982; Critchley et al., 1992), also in light of upcoming
climate changes (Stockholm Environment Institute, 2009).
A wide variety of rainwater harvesting technologies have been studied and described in detail – from zaï
pits in Nigeria to demi-lunes in Niger, through to negarim catchments in the Negev desert of Israel and
teras systems in Tunisia (for an overview see e.g. African Development Bank, 2007) – yet one form has
received little attention thus far: road runoff harvesting.
6
1.2 Research questions
The overall aim of this thesis is to shed more light on the performance and potential of road runoff
harvesting. This technology is currently practiced by a number of farmers in sub-Saharan Africa (an
overview is provided in the next chapter). From literature case studies, however, it remains unclear what
the precise impacts are of these road runoff harvesting systems. Furthermore, an assessment has never
been made of the potential for up-scaling the use of this technology throughout the drylands of subSaharan Africa, either for use by smallholder farmers (practicing rainfed agriculture in cultivated lands) or
by pastoralists (keeping livestock in the dryer rangelands).
This thesis focuses on the question what the potential is for practicing and up-scaling road runoff
harvesting in sub-Saharan Africa. More in particular, the research carried out for this thesis aimed at
giving an answer to the following two sub-questions:
1) What is the performance of existing road runoff harvesting systems in terms of sustainability?
2) What is the (bio)physical potential for up-scaling the use of road runoff harvesting in the drylands
of sub-Saharan Africa?
The first question addresses the potential of the technology itself, while the second question focuses on
the feasibility of areas where the technology is not practiced as yet. The latter question is limited to the
physical potential, i.e. social, economic and detailed environmental (hydrology, soil types) are not
included. Assessment of the physical potential for increasing the adoption of road runoff harvesting is
done with data on roads from literature and online databases. The performance of existing technologies is
tested by means of case studies in Eastern Province, Kenya. Providing an answer to these questions will
help to understand the desirability of promoting this technology amongst smallholder farmers, policymakers and development agents alike.
1.3 Thesis structure
In Chapter 2, the concept of road runoff harvesting is explained in detail and an overview is given of the
existing knowledge on road runoff harvesting systems in sub-Saharan Africa. Chapter 3 presents the
methodology that has been applied to address the two research questions: first the approach for the case
studies is described, followed by the methodology that was used to assess the potential for up-scaling
road runoff harvesting. Subsequently, in Chapter 4 the data are presented that have been gathered from
the case studies (and additional sites that have been visited) as well as the results from the sub-Saharan
Africa-wide assessment. Analysis of these results is provided in Chapter 5: the case studies are
evaluated according to four criteria (Technical performance, Economic viability, Environmental
friendliness and Social acceptance). The results of the assessment are directly discussed in Chapter 6,
together with the outcomes of the performance analysis. The conclusions are presented in Chapter 7.
Lastly, recommendations are given for researchers, policy-makers and development agents in Chapter 8.
7
2. Road runoff harvesting in sub-Saharan Africa
2.1 The concept of road runoff harvesting
The concept of road runoff harvesting is relatively new to researchers and development agents. In recent
years, the first case studies have appeared in literature that describe the way smallholder farmers gather
and use runoff from roads. This chapter gives an overview of the current knowledge on road runoff
harvesting that is available from literature and other sources. As the case studies in following sections will
show, road runoff systems are often the result of farmer innovations.
Road runoff harvesting is a form of rainwater harvesting. The principle of rainwater harvesting is based on
three steps (see also Figure 2):
1. Collecting and concentrating runoff
2. Storing runoff (optional)
3. Using the runoff for agricultural production or other purposes
In other words, a rainwater harvesting system is composed of a catchment, an optional storage facility
and a cultivation area. In the context of this thesis the term “cultivation area” is used to designate the area
where the runoff is applied for agricultural production. This is done to clearly distinguish the cultivation
area of rainwater harvesting systems from “cultivated lands” that are used as a category for assessing the
potential for up-scaling the use of road runoff harvesting in the drylands of sub-Saharan Africa (see
section 3.5).
The purpose of rainwater harvesting is to make more efficient use of rainwater that would otherwise be
1
lost as runoff or through evaporation. Two general forms of rainwater harvesting can be distinguished :
water harvesting with microcatchments (within-field) and with external catchments (Critchley and Siegert,
1991). The first is further characterised by the length of the catchment that is usually a few meters long,
while the length of an external catchment is often 30 meters or more.
Figure 2. The principle of rainwater harvesting
This figure shows the principle of rainwater harvesting (after Critchley and Siegert, 1991). In the case of road runoff
harvesting, the catchment is formed by a road and/or by the sides of this road.
1
NB. Rainwater harvesting also includes rooftop harvesting. However, because the focus of this thesis is on
rainwater (runoff) harvesting from land surfaces, roads and road sides in particular, rooftop harvesting is not
discussed.
8
Gathering rainwater with the help of roads falls in the category of external catchments as runoff is
collected outside the cultivation area. Following Critchley and Siegert’s definition for water harvesting
(Ibid.), road runoff harvesting can be briefly defined as: “the collection of runoff from roads and roadsides
for productive purposes”.
Roads (and roadsides) refer to all types of transportation ways, from motorways through to rural roads to
footpaths and livestock trails. Smaller roads and footpaths are often connected to house compounds that
2
can also contribute to the collection of runoff . Roadsides refer to the area adjacent to the road that
contributes to the amount of runoff that is gathered along the border of the road.
Productive purposes refer to crop production for subsistence, for cash crops (including kitchen
gardening), for fodder production. Runoff stored in a reservoir can also be used for livestock to drink and,
provided it is clean enough, also for domestic use.
Box 2. Methods for calculating the potential amount of road runoff and the cultivation area size based on rainfall
depth, runoff efficiency and crop water requirements
The amount of runoff that can be harvested in a catchment can be calculated as follows:
Where:
Pd: Design Rainfall (generally in mm)
K: Runoff Coefficient (no unit)
E: Efficiency Factor (no unit)
The Design Rainfall is the amount of rainfall (in mm or m) during the growing season, which should be
enough to meet the ‘Crop Water Requirement’ (ETc) that is expressed in mm/day (or m/day). The Design
Rainfall is often calculated for a certain probability level, by looking at the rainfall over a number of years.
The Runoff Coefficient is determined by how much runoff (in mm) can be generated with a certain amount
of rainfall (in mm). It is defined as the runoff divided by the rainfall in a given catchment area. It depends on
how much of the rainwater is absorbed by the soil; it will therefore also change depending on the length of
a shower. A tarmac road with a 10% slope has a large runoff coefficient of 0.9 or more, while for a sandy
road with a 3-5% slope this will be more or less 0.2-0.3.
The Efficiency Factor takes into account factors that negatively affect the amount of runoff that can be
generated, like the inefficient distribution of runoff, evaporation and deep percolation. Generally, this factor
is set between 0.5 and 0.75.
With the same parameters, the catchment/cultivation area (C/CA) ratio can be calculated (Ibid.):
Where:
ETc: Crop water requirement
Broadly speaking, the C/CA ratio in a microcatchment (within-field) varies between 1/1 and 3/1, while for
external catchments the ratio tends to be larger (2/1 – 10/1; Critchley and Siegert, 1991).
2
This thesis does specifically not focus on rainwater harvesting systems that are based on runoff collection from
house compounds and court yards, such as the ‘water borne manuring systems” described by Mutunga and Critchley
(2001).
9
The water that can potentially be harvested in a catchment determines the size of the area where crops
can be grown (Boers and Ben-Asher, 1982). Box 2 explains how the potential amount of runoff can be
calculated, and how the ratio between catchment and cultivation area can be determined.
Like other forms of water harvesting, the collection of road runoff is suitable in areas of low rainfall in the
arid, semi-arid and dry sub-humid areas of sub-Saharan African.
Road runoff harvesting itself can be divided into two categories:
A. Runoff harvesting with roadside drain
Rainwater is collected primarily from the surface of the road
B. Runoff harvesting with culvert
Rainwater is collected in the uphill area adjacent to the (rail) road
2.2 Runoff harvesting with roadside drain
Roads have a large surface that can collect large amounts of rainwater. Rainwater that is not directly
‘absorbed’ by the road and runs off the road, can be collected. In the rainy season, smaller roads can
become completely inaccessible and turn into small rivers. The amount of available runoff can be
calculated in a relatively simple way and depends on the runoff coefficient (see Box 2). If the camber of a
road is convex, only half of the road can be used to collect rainwater. Depending on the potentially
available runoff one can determine the proportion of land and the amount and type of crops that can be
cultivated. Figure 3 shows the basic forms of runoff harvesting from roadside drains.
Examples from the field show that a large variety exists in the application of roadside drains. In Uganda
small drains are used that lead to square soak-away pits with banana plants (Kiggundu, 2002; Critchley et
al., 1999). In Kenya similar pits are known as T-basins according to Bittar (2001, cited in: Mati, 2005). The
majaluba system in the semi-arid regions of Tanzania (Mwanza, Shinyanga, Tabora, Singida, Dodoma) is
based on (road) runoff collection into retention basins (FAO, 2001; Hatibu and Mahoo, 2000 and Hatibu et
al., 2000). The bunds of the majaluba, which are used to grow paddy rice, are reinforced with Cynodon
dactylon grass.
Figure 3. Runoff harvesting with roadside drains: three basic forms
This figure shows three basic forms of road runoff harvesting with a roadside drain. Blue arrows indicate the direction
of the runoff water. The first form (a.) applies water directly in small, restricted cultivation areas (planting pits, Tbasins or retention basins) alongside the road. The second (b.) guides the water into retention ditches that are built
along the contour lines. This form also includes flooding of the cultivation area, which can have contours bunds
instead of trenches. The third and last form (c.) consists of an intermediate storage facility (see examples in text) that
is preferably built above the cultivation area (to facilitate irrigation). Many variations are possible based on these three
general forms.
10
Critchley et al. (1992) describe the caag system in Hiraan Region, Central Somalia, that is based on
(road) runoff diversion into a field where the runoff is guided in a zig-zag manner along earthen bunds
that are built at a small angle following the contour lines (similar to Figure 3b.)
Other examples of run-off farming with roadside drains are found in Machakos District, Kenya, where
runoff is first guided into one or more retention ditches that are built along the contour lines; in the
retention ditches pits are dug for banana plants (Ngigi, 2003a: 144). Two farmers have, each of them,
created a system where water flows from the first ditch (uphill) to the next ditch once the first is full. Water
input is regulated either automatically (it spills over in the next ditch) or manually (by blocking the entry of
a ditch with a gunny bag). Retention ditches vary in size (from 50 cm by 50 cm to more than 1 m by 1 m
in cross section) and can be excavated with soil thrown uphill (fanya juu) or downhill (fanya chini). Long
ditches are generally constructed with a small gradient. Banana pits can be dug in or next to the ditch.
Pawpaw, mango, citrus and guava trees are grown on the embankment, while maize and beans are
cultivated on the terrace in between ditches (along furrows that run parallel to the ditches) (ICRAF, 2012).
Instead of storing the runoff directly in the soil profile, water can also first be stored in a reservoir before it
is used for supplemental irrigation. The guide “Water from roads” by Nissen-Petersen (2006) describes a
variety of water reservoirs, such a borrow pits along roads and water pans (natural depressions, called
hafirs in Kenya), but also reservoirs especially constructed for this very purpose, like: earth dams
(murram pits, ponds, charco dams, hill side dams), above and underground water tanks in many forms
and shapes (e.g. berkads in Somalia), and hand-dug wells near Irish bridges (concrete drifts that function
as a bridge for traffic and, concomitantly, as underground and/or aboveground dam). In Lare District,
Kenya, for instance, hundreds of ponds are used to store all kinds of runoff (including from roads)
(Malesu et al. 2006). An example from a borrow site that was turned into a dam comes from Tigray,
Ethiopia, where farmers have started using it for feeding the water to their livestock (Haile et al. 2000,
cited in: Mati, 2005). Hatibu et al. (2000) also report the use of several borrow pits for road runoff
harvesting along several highways in Tanzania.
Many of the examples above indicate that the origin of road runoff harvesting from roadside drains lies
almost exclusively in the innovative minds of smallholder farmers, who recognise and exploit
opportunities for using road runoff for productive purposes.
2.3 Runoff harvesting through a culvert
This form of road runoff harvesting can be practiced where road construction workers have placed one or
more culverts under a (rail) road. Figure 4 shows the basic forms of water harvesting from a culvert outlet.
Culverts are conduits constructed under (rail) roads for drainage purposes: they aim to channel water
from the uphill side to the downhill area on the other side of the road. They can have various shapes,
lengths and diameters, and are generally made of concrete, polyvinyl chloride, steel or stone. The size of
a culvert depends on the amount of runoff that it has to handle – for large quantities bridges have to be
constructed. Jungerius et al. (2002) report an average diameter of 0.9 metre along a 42 kilometres long
stretch of road north of Nairobi, Kenya (more details on this road are presented below). Though culverts
are built to prevent roads from being flooded, they often cause harm to the downhill field due to the power
of the concentrated runoff they discharge. The huge quantities of water that are released from a culvert
when it rains heavily, can lead to gully formation and severe erosion if the water is not slowed down or
controlled in another way (see Figure 5).
11
Figure 4. Runoff harvesting through a culvert: two basic forms
This figure shows two basic forms of road runoff harvesting based on the water that is discharged by a culvert. In the
first form (a.), the water is guided directly into retention ditches for use within-field. In this case, spill-ways are
essential to prevent waterlogging. The other form (b.) makes use of an intermediate water reservoir that can have all
forms and shapes (see examples in the text under harvesting with a roadside drain), while the size depends on the
amount of runoff water that needs to be stored.
A technical handbook of the World Bank (1997) touches upon the cumulative environmental impacts that
could arise from poorly designed culverts or drainage systems along a road located in a watershed. Yet,
the handbook mainly focuses on the impacts on the road itself, in particular the flooding of a road due to
accumulation of sediment at the inlet of a culvert, and on the migration pathways of animals that use
culverts to cross a road. Potential erosion and the formation of gullies on the downstream side of the road
are not discussed in the handbook.
Controlling the potentially devastating power of runoff from a culvert is crucial. Otherwise, when runoff
from culverts is not properly managed, a situation like along the Tanga-Arusha highway can arise where
55 culverts have created deep gullies in the landscape downstream of every culvert (Hatibu et al., 2000).
Moreover, attempts of farmers to divert the water from gullies onto their lands – with the aim to increase
agricultural production – have resulted in destruction of their farm land. Another example of gully
formation is provided by Jungerius et al. (2002), who report that 13 out of 24 culverts have led to
downslope erosion along a 42 km long earth road between Marich Pass and Kerio Valley in Kenya.
Nevertheless, the effects of road construction on erosion remain largely unstudied.
Once gullies have formed, measures can be taken to reclaim them to avoid further land degradation and
to benefit from the concentrated runoff. Gully reclamation through the construction of check dams would
be an option (see e.g. WOCAT, 2007). Further erosion can also be prevented by adding vegetative
measures like grass to the water way (Ibid.). Diversion into a borrow pit, dam or pond would be another
option in order to stop the water and store it for later use.
If gully formation has not yet taken place, then runoff can be used directly for agricultural purposes. The
Lusilile Irrigation Project is a successful initiative in Manyoni District, Tanzania, that exploits water coming
from two railway culverts (Hatibu et al., 2000). For this purpose, a series of canals (almost 20 km
altogether) was constructed to divert the water to a cultivation area of 150 ha where paddy rice is
produced. Despite an initial increase in production, the system of canals was not designed for the El Niño
rains during the same season and some canals were damaged.
12
Figure 5. Picture of a gully formed at the outlet of a culvert
This picture was taken by Erik Nissen-Petersen in Maasai land (source: Nissen-Petersen (2006)). The gully results
from the destructive power of water that is discharged by a culvert into a field located on the valley side of a road.
Another example is that of Mr. Muindu Musyoka (Mutunga and Critchley, 2001). He owns a farm in
Mwingi District, Kenya, and has developed a form of road runoff harvesting using a culvert under a main
connector road. He constructed a diversion ditch (with the fanya chini technique), through a neighbouring
field, that leads the water from the culvert to his own cultivation area. This farm has been revisited for the
purpose of this thesis.
Due to the fact that this form of road runoff harvesting depends on the presence of culverts, runoff
harvesting through culverts most likely originated only recently – up to a few centuries ago at most –
when the first culverts were built. The case of Muindu Musyoka shows that farmer innovation may be an
important if not crucial factor for using road runoff harvesting. From the information provided by Hatibu et
al. (2000) is not clear what the driving factor behind the Lusilile Irrigation Project has been, though the
development agents may play a role in setting road runoff harvesting as well.
The runoff that is collected by means of a culvert can be calculated by determining the average runoff
coefficient and the surface of the area that generates the runoff. The same calculation method as
described in Box 2 can be used to estimate the amount of runoff.
2.4 Benefits of road runoff harvesting for smallholder farmers
Ngigi (2003a: 217) states that “the capacity of road runoff harvesting to provide food security is immense
for some farmers in Kitui and Machakos Districts (Kenya). The farmers, who previously suffered
persistent crop failures even during normal rains, report improved yields.” There thus seems to be a great
potential for this technique to improve the lives of smallholder farmers living in the dry areas of subSaharan Africa.
13
Existing case studies point at the promising impacts of road runoff harvesting on the lives of smallholder
farmers. In Machakos District, for instance, a farmer named Mr Nzove now manages to yield 40 large
bunches of bananas per month, as opposed to the 10 small bunches he would otherwise produce. In
addition, he produces three times as much coffee as before (Ngigi (2003a: 215). With road runoff
harvesting, his monthly income attained US$ 80 (Ibid.: 224).
The same author mentions the improved welfare of Ms Angeline Muthue, who also lives in Machakos
District. A higher income from the sales of banana, vegetables and pawpaw (US$ 40 per month) has
enabled this farmer to create employment for her children with the opening of a butchery and a hardware
store. A rough comparison of the Muthue’s yields with the average yields of farmers in the area shows a
significant impact of road runoff harvesting on her produce (see Table 1). Though this table provides a
very limited picture, it is the most detailed comparison of yields that was found in literature.
Table 1. Comparison of yields obtained with and without road runoff harvesting
Ms Muthue’s farm production (kg)
Average neighbours’ farm production (kg)
Crop
Beans
2,340
90
Maize
450
10
Cowpeas
200
20
Green grams
100
10
Pumpkin
1000
0
This table compares the production of a farmer in Machakos District using road runoff harvesting with the production
of her neighbours (source: Ngigi, 2003: 218). The data correspond to the harvest during the long rainy season in
2002 (April-May).
In the earlier mentioned Lusilile Irrigation Project, significantly higher yields were recorded after the
construction of the channels. By 1997/98, 145 farmers benefited from a yield increase from 1 to 3.5 metric
tonnes per hectare (Hatibu et al., 2000).
Nissen-Petersen (2006) lists other benefits that could arise from road runoff harvesting, besides income
from the cultivation of crops and fruit trees:
-
Selling water to neighbours
Raising ducks, geese, fish and bees in or near open water reservoirs
Recharge of wells or dams
At the same time, the same author warns for potential health hazards associated with runoff harvested
from tarmac roads that could contain traces of tar, oil and rubber. The process and impacts of pollution
through road runoff harvesting remain largely unstudied.
2.5 Upstream-downstream impacts of road runoff harvesting
The collection of rainwater in upstream catchments (like roads and roadsides) can have both positive and
negative consequences for downstream areas (e.g. SIWI, 2001; Rockström et al., 2003, Bouma et al.,
2011). One impact can be that less runoff reaches the fields downhill, which can cause problems for
water users like smallholder farmers. An example of such a situation comes from Kenya, where banana
growers along the roadsides get into conflicts because too much water is ‘tapped’ from the uphill-side of
the road (Ngigi, 2003a: 213). The same author even argues that “[…] in most cases of road runoff
harvesting there is an offended neighbour who now realizes the crop on his/her own farm could perform
better with extra input in form of road runoff.” He mentions (ibid.) the case of Mrs. Musyoka in Kitui
District, Kenya, who used to divert all runoff from a road, thus leaving no water for her downstream
14
neighbours. The local administration had to intervene to settle the case: they advised the farmers to find
an agreement to equitably share the water. He also reports of a similar case involving three farmers along
an earth road in Laikipia District in Kenya (Ngigi, 2003a: 212). While such conflicts are becoming more
common in Laikipia District, “[t]he water laws in most countries of GHA [Greater Horn of Africa] do not
provide policy guidelines on runoff sharing as anyone is free to harvest as much runoff as possible
without seeking permission from government authorities” (Ngigi, 2003a: 191). Equitable sharing of runoff
from roads may thus represent a challenge in areas where several farmers exploit runoff from the same
road drain – or culvert for that matter.
The opposite consequence may be that a community living downstream receives more water owing to the
fact that more rainwater can infiltrate the soil in the uphill area and – provided that the permeability of the
ground is good enough – reaches the downhill area via the underground streamflow. Rainwater
harvesting may thus influence the ecosystem services like (downstream) water provision provided by a
watershed. Indirectly, by altering the amount of groundwater, runoff and evapotranspiration, it will have an
impact on other ecosystem services (e.g. soil conservation and nutrient cycling) as well.
Up-scaling of rainwater harvesting technologies in a watershed may further change its hydrology. A
modelling study by Mutiga et al. (2011) suggests that in the upper Ewaso Ngiro North basin only
moderate effects can be expected from expanding the use of rainwater harvesting (which in this study
3
includes in-situ water conservation techniques ). The study of the upstream and downstream
consequences of rainwater harvesting, and road runoff harvesting in particular, has started to receive
attention only in recent years. Concomitantly, policies are lacking to address conflicts that are the results
of downstream impacts of upstream water harvesting (Rockström, 2000).
2.6 Adoption by other farmers
Farmers around the world have adopted road runoff harvesting (see examples in Box 3). Besides the
above-mentioned examples from East Africa (Kenya, Tanzania, Uganda) it is not known how many other
smallholder farmers in sub-Saharan Africa practice road runoff harvesting, nor is it clear whether there is
trend regarding adoption by other farmers. A video produced by ASAL Consultants (Nissen-Petersen,
2010) tells that road runoff harvesting is a commonly used technique in the African drylands. As far as
Kenya is concerned, this is corroborated by Shaxson and Barber (2003) who write that “the most common
and successful concentrated runoff harvesting practice in Kenya is the harvesting of road runoff in
retention ditches”. Besides the earlier examples from Machakos, Kitui and Mwingi Districts, road runoff
harvesting is widely practiced in Lare Division of Nakuru District, Kenya (Malesu et al., 2006). Here, runoff
is harvested by farmers from hillsides and roads and stored in ponds (and pans) that are used for
supplemental irrigation. Tuitoek et al., 2001 (cited in: Mati, 2005) writes that 1,000 pans have been
installed in Lare Division to trap road runoff. With reference to a publication of the Ministry of Agriculture
from 2001, Ngigi (2003a: 76) writes that 4,000 hectares in Kitui District benefit from road runoff
harvesting.
3
In situ water conservation techniques are within field measures that prevent rainwater and runoff from leaving the
field, like mulching and growing continuous ground cover (e.g. as part of conservation agriculture).
15
Box 3. Road runoff harvesting in other parts of the world
The technology is not only practiced in arid regions of Africa; other parts of the world have developed their
own ways to collect rainwater from roads. Already in 1995, FAO organised a workshop where road runoff
cases from Argentina, Brazil en Venezuela were discussed (UNEP, 1997). India has a long history when it
comes to water harvesting technologies; nevertheless, road runoff harvesting is not mentioned explicitly in
the standard work ‘Dying Wisdom’ (Agarwal, 1997). Sachdeva and Sharma (2008) do present a case for
road runoff harvesting in India, yet only for urban areas. In Gansu Province, China, road runoff is collected
and stored in tanks for supplemental irrigation of crops and trees (Qiang and Yuanhon, 2003).
Also in industrialised countries like the United States of America farmers make effective use of road runoff
(see e.g. Zeedyk (2006). The technique is also incorporated in the functioning of modern ‘vinex’ living
quarters in The Netherlands, where water from roads is collected and cleaned before it is released back
into the environment.
Regarding Tanzania, “tapping road runoff for supplemental irrigation [of] crops is widespread”, as stated
in SIWI (2002, cited in: Mati, 2005). For Uganda, Critchley et al. (1999) refer to earlier observations that
water harvesting from roads and paths for banana plantations has been practiced by “many people” for
decades. For other countries in sub-Saharan Africa indications about the occurrence of road runoff
harvesting have not been found.
Information about the factors influencing adoption of road runoff harvesting is limited and scattered.
Mugerwa (2007) studied the adoption factors of soil and water conservation measures, including runoff
diversion from roadside drains into retention ditches, in banana plantations in Kiboga and Masaka
Districts in Uganda. He identified the following barriers that explain the low adoption rate of (road) runoff
harvesting technologies:
•
•
•
•
•
•
•
Use of simple tools (hand hoe) vs. more sophisticated tools required for establishing runoff
harvesting structures
High labour costs vs. low income from the sales of banana
Low actual yield increase vs. expected yield increase
Low market prices of banana
Lack of government support; extension service receive inadequate funding and consider
rainwater harvesting as ‘soft and inappropriate’
Lack of donor support due to the low priority (road) runoff harvesting receives
Lack of financial incentives such as credit
Mugerwa remarks that socio-economic factors like produce sharing, jealousy and witchcraft were not
accounted for in his study, yet could also play a role.
For soil and water conservation measures in general and rainwater harvesting in particular, some factors
discouraging adoption have been summarised by Critchley (2009) based on two earlier reviews and
personal experience. These (broadly defined) barriers include poor project design, lack of technical
knowledge, inadequate institutional and policy support, and economic barriers. Furthermore, Ngigi et al.
(2005a) emphasize the importance of matching technical ‘solutions’ with the actual priorities of farmers,
who are generally risk-averse and consider other options to sustain or improve their livelihood as well.
There is a multitude of factors that influence the decision of a farmer to adopt rainwater harvesting
measures (e.g. Ngigi, 2003), which vary from region to region owing to differences in technical, social,
cultural, economic and environmental conditions. Broadly speaking, the same factors also apply to road
runoff harvesting in particular. Nevertheless, some factors are specific for road runoff harvesting for
obvious reasons (e.g. proximity of and access to a road or culvert). In this thesis, some adoption factors
specifically related to the road runoff harvesting case studies will be presented.
16
2.7 Impacts of up-scaling
Little is yet known about the impacts of scaling up rainwater harvesting. Ngigi (2003b) discusses a case
study in Wajir District, north-eastern Kenya, where water pans have been constructed for communities
that are predominantly pastoral. The reduced need for water from other sources as a result of water
harvesting has led to increased harmony between different clans. Normally, these clans would compete
over the limited water resources – and competition is growing since more farmers are shifting from
livestock to crop production. The author concludes that scaling up water harvesting may act as a conflict
mechanism in water scarce areas.
From a theoretical perspective, Ngigi et al. (2007) propose a framework for modelling the hydrological
impacts of up-scaling rainwater harvesting in a river basin, allowing indirectly also to assess the socioeconomic and environmental consequences. The upper Ewaso Ng’iro river basin in Kenya was chosen as
a case study to design scenarios for river flows. The scenarios are based on the assumptions that
adoption will increase over time and river flows will decrease as a result. An important factor in the model
are the downstream water requirements, that is chosen as an indicator – with the aim to assist decisionmakers – in order to intervene in time in upstream water harvesting activities (i.e. once the downstream
water requirements are no longer met). Practical applications of this model have not yet been reported.
Focusing on the same basin, Mutiga et al. (2011) looked at the hydrological responses to land use
change (rainwater harvesting) using the soil and water assessment tool (SWAT) model and satellite
imagery covering a period of sixteen years. The outcomes show that scaling up rainwater harvesting has
no significant impacts on downstream areas, despite a 5% increase of base flow and 2% decrease in
surface runoff.
These studies highlight the fact that research on the impacts of up-scaling rainwater harvesting
technologies is still in its early stages. In this context, road runoff harvesting in particular was not found in
any study or report.
17
3. Methods
3.1 Analysis framework for case studies
To answer the first sub-question – “What is the performance of existing road runoff harvesting systems in
terms of sustainability? – the criteria for identifying environmentally sustainable technologies (ESTs)
developed by UNEP were chosen as a starting point (UNEP, 2003). According to these criteria, a
technology should be environmentally sound, economically viable and socially acceptable (Ibid.). In other
words, an EST should positively contribute to the economic, natural and social capital of its environment.
Regarding the evaluation of water harvesting technologies, several authors (e.g. Critchley and Siegert,
1991; Oweis et al.,1999; Rockström, 1999 and Hatibu et al., 2000) indeed emphasize the importance of
taking into account the related socio-economic and environmental issues.
Initially, the framework of the World Organisation for Conservation Approaches and Technologies
(WOCAT; WOCAT, 2007) was envisioned as the analysis framework. The WOCAT Questionnaire on
SLM Technologies (WOCAT, 2000) was used for collecting data for the case studies. This questionnaire
is structured in three parts: General Information, Specification of the SLM technology and Analysis of the
SLM technology (see Annex I, first column). To systematically address the technological, economic,
environment and social aspects, this framework was not deemed practical. Instead, during the course of
this study, it was decided to use the TEES-test developed by Critchley (2007; see Table 2, left column),
which incorporates the three sustainability criteria as well as a technical performance criterion – which is
essential for assessing the long-term performance of a technology like road runoff harvesting.
For this reason, the data gathered with the questionnaire have been classified according to the categories
of the TEES-test (see Annex I; NB: general information on the technology was put in a fifth category
called ‘General’). In addition, the elements of the questionnaire were structured according to 3 to 5 subcategories under each criterion. The result of this classification – in terms of input for the TEES-test – is
presented in Table 3.
For the Technical feasibility these are (physical) Conditions, Purpose (of the Technology), Measures
(including potential runoff and catchment/cultivation ratio) and Knowledge required. For the Economic,
Environmental and Social data three sub-categories are used: Conditions, Benefits and Disadvantages.
The Conditions describe the characteristics of the area where the technology is applied and do not regard
the impact of the technology. The Benefits and Disadvantages instead cover the consequences of using
road runoff harvesting. In addition, for the Economic data the sub-category Costs was used, and for the
Social data the two sub-categories Origin (of the innovation) and Adoption (by other farmers) were used.
Analysis of these data was done using the approaches and tools described in Table 2.
Table 2. Approaches and tools used to analyse each of the TEES-test criteria
Criteria of TEES-test
Technical performance
Economic viability
Environmental friendliness
Social acceptance
Analysis approach/tool
Comparison physical conditions
Performance of collection, storage and use measures
Comparison level of knowledge required
Comparison economic conditions
Quantitative benefit-cost analysis, similar to Ngigi et al. (2005a), taking
into account economic disadvantages
Comparison environmental / ecological conditions
Qualitative comparison benefits and disadvantages
Comparison social conditions
Qualitative comparison benefits and disadvantages
18
Table 3. Methodology used to categorise data from the WOCAT Questionnaire on SLM Technologies
Sub-category
Elements of QT
GENERAL
•
NA
•
Common name, local name, part of watershed,
Approach, area definition, coordinates, definition of
Technology, photos
TECHNICAL
•
Conditions
•
•
Purpose
•
•
Measures
•
•
Knowledge required
•
Rainfall, climate, growing seasons, altitude, land
form, slope, soil: depth, texture, fertility, organic
matter, drainage, water storage capacity;
groundwater table, surface water availability, water
quality
Problems, land use type, goals, land degradation
type, causes of land degradation
Conservation measures (agronomic, vegetative,
structural and /or management), measures against
land degradation; type and layout; establishment
and maintenance activities
(including potential runoff, catchment / cultivation
area ratio)
Knowledge required
•
Conditions
•
•
Costs
•
•
Benefits
•
•
Disadvantages
•
Level of wealth, significance of off-farm income,
access to services and infrastructure, market
orientation, land use tools, type of cropping system,
water supply, size of cropland
Establishment costs, maintenance costs, costs of
agricultural input
Production and socio-economic benefits, benefits
vs. establishment and maintenance costs
Production and socio-economic disadvantages
ENVIRONMENTAL
•
•
•
Conditions
Benefits
Disadvantages
•
•
•
Biodiversity (and other)
Ecological benefits
Ecological disadvantages
SOCIAL
•
Conditions
•
•
•
•
•
Origin
Benefits
Disadvantages
Adoption
•
•
•
•
Type of land users applying Technology,
population density, pop. growth, land and water
rights
Origin (of idea/innovation)
Socio-cultural benefits
Socio-cultural disadvantages
Adoption (including acceptance)
ECONOMIC
In this table the elements of the WOCAT Questionnaire on SLM Technologies (third column) are categorized
according to the four categories of the TEES-test (see text) plus a general category (GENERAL) listed in the first
column. In addition, the elements are divided into a number of sub-categories (second column) to facilitate
comparison. Annex I shows, question per question, how the elements have been categorised.
19
3.2 Selection of case studies
Two case studies were identified to assess the performance of road runoff harvesting. The first is a revisit
of an existing case study in Mwingi District, Kenya, first described by Mutunga and Critchley (2001). This
site was chosen to study 1) runoff harvesting through a culvert, and 2) the long-term impact of road runoff
harvesting on a single farm. The second is a road runoff harvesting system with roadside drains in
Machakos District that has never been described before. It was not possible to identify more case studies
in the same area prior to the field visits. In addition, during the field trip four other sites in Machakos
District were identified as well that provide additional information about the possibilities that exist to use
and adapt road runoff harvesting to local conditions. Figure 6 shows where the six sites are located.
It is important to note that these six sites show examples of road runoff harvesting that have in one way or
the other succeeded. For this reason, they have been identified during fieldwork of researchers. Though it
would be particularly useful to study examples of sites where the adoption of road runoff harvesting has
failed, such failures are seldom reported or described.
Nevertheless, the information from the six sites provides some insight into the performance and potential
impact of road runoff harvesting for smallholder farmers and their environment.
Figure 6. Map showing the location of the visited farms
The map in the upper right corner shows the location of the case studies (#1 and #2) and of the four additional sites
(#3 – #6) that were visited during the fieldwork.
20
3.3 Study area
The semi-arid agro-ecological zones of Mwingi and Machakos Districts (Eastern Province, see Figure 6)
are located at an altitude of 400-1800 m and 1000-1600 m respectively (Pretty et al., 2011). Annual
rainfall depths of 400-700 mm (Ibid.), which are higher in the highlands (Tiffen et al., 1994). Two rainy
seasons are distinguished: a ‘short’ season from October to December and a ‘long’ season from March to
May (Critchley, 1991). The main staple food is maize, which is often mixed with cowpeas and pigeon
peas, and also with beans, green grams, millet, and sorghum (Muhammad et al., 2003). Livestock is
reared by pastoralists on rangelands (e.g. the eastern part of Mwingi District) and by farmers in the
cultivated areas. The people living in these districts belong mostly to the Akamba tribe (Tiffen and
Mortimore, 1994).
Machakos District has become known all over the world because it has managed to increase agricultural
production in the period 1930-1990 despite a more than twofold population increase and problems with
agricultural lands that used to suffer from severe erosion (Ibid.). Over 70% of the land has been turned
into fanya juu terraces (Critchley, 1991). Other soil and water conservation measures, such as grass
strips, contour ploughing and agroforestry have also contributed to the success. The district (which is
divided into Machakos and Makueni Counties) has a total population of 1,983,111. Machakos County has
a population density of 176.96 persons per square kilometre and in Makueni County the density is 110.45
persons per square kilometre (Kenya National Bureau of Statistics, 2012).
Mwingi District has not received as much attention from researchers as Machakos District. In Mwingi
District, Kamba herders are the dominant group, followed by Orma and Somalis (Opiyo et al., 2011). The
district has a population of 303,828 and an average population density of 28 people per square kilometre
(Kenya National Bureau of Statistics, 2012).
3.4 Fieldwork and interviews
Farmers were visited on-site and interviewed with the WOCAT Questionnaire on SLM Technologies.
Translation from English to Kikamba or Kiswahili and back was done by an interpreter (Ms Rose Mueni).
Table 4 shows the order and dates of the six visits.
Table 4. Timing of field visits and type of interviews
#
Farmer
Date(s)
1
Muindi Musyoka
9 - 13 May 2011
2
Mwema Maswili
18 May 2011
3
Samuel Mweu Maingi
17 May 2011
4
Neighbour of Samuel Mweu Maingi
17 May 2011
5
David Kyula
18 May 2011
6
Mr. Sammy
18 May 2011
(QT: WOCAT Questionnaire on SLM Technologies
21
Type of interview
QT*
QT*
Open interview
Open interview
Open interview
Open interview
3.5 Methodology for determining the potential for up-scaling road runoff
harvesting
To answer the second sub-question, “What is the (bio)physical potential for up-scaling the use of road
runoff harvesting in the drylands of sub-Saharan Africa?”, a simplified approach was taken to estimate the
length of roads in the drylands of sub-Saharan Africa and their potential for generating runoff for road
runoff harvesting purposes. Though more elaborate approaches for mapping the potential for water
harvesting have been considered, involving GIS-tools for instance (e.g. Gupta et al., 1997, Ziadat et al.,
2006), this was not possible within the scope of this study.
Figure 7. Methodology used to determine the suitability of roads for runoff harvesting
The flowchart describes the methodology that was used to determine the suitability of roads in sub-Saharan Africa for
road runoff harvesting. Besides the first step (determination of the size of the dryland area in each country), all the
data are estimates.
The suitability of roads in sub-Saharan Africa for road runoff harvesting was estimated using the steps
shown in the flowchart of Figure 7. This process was carried out for all individual countries in sub-Sahara
Africa, most of which have drylands on their territory. Railways have not been incorporated in the
assessment, as they represent only a small fraction of the total network of roads (less than 1%, according
to data from the online World Bank database only). Considering the fact that this assessment is meant to
provide a rough estimate of the potential for up-scaling road runoff harvesting, the fraction of agricultural
land under irrigation (less than 5%) was not taken into consideration for the calculations.
The ‘mapping’ of roads and culverts that could be suitable for road runoff harvesting was done as follows.
First, the area of drylands per country in sub-Saharan Africa was calculated. In literature several
definitions of ‘drylands’ are used. For the purpose of this thesis, drylands are defined as arid, semi-arid
and dry sub-humid zones, following the categorisation of FAO (1993). These three areas correspond to
the agro-ecological zones where rainwater harvesting is generally practiced. Table 5 gives an overview of
the main characteristics of drylands.
22
Table 5. Characteristics of arid, semi-arid and dry sub-humid areas
Annual rainfall**
(in mm)
Plant growing period****
(in days)
Arid
Aridity Index*
(precipitation / potential
evapotranspiration)
0.05 - 0.2
Up to 300
Less than 75
Semi-arid
0.2 - 0.5
200-800
75 - 115
Dry sub-humid
0.5 - 0.65
Upper range around 1000***
115 - 179
Drylands
0.05 - 0.65
Up to 800
(excluding dry sub-humid areas)
Up to 179
Sources: *UNEP (1992), ** adapted from FAO (1989), ***Rockström (1999) and ****FAO (2000)
The starting point for calculating the length of the road network in the drylands was the length of the
national network of which the most recent figures can be found in the database of the World Bank (World
Bank, 2012). Though on its website, the World Bank states that “Total road network includes motorways,
highways, and main or national roads, secondary or regional roads, and all other roads in a country. A
motorway is a road designed and built for motor traffic that separates the traffic flowing in opposite
directions.”, this does not correspond to figures found for Kenya. For this country, figures from the World
Bank database only refer to classified roads. In Kenya, classified roads include International Trunk
Roads, National Trunk Roads, Primary Roads, Secondary Roads, Minor Roads and Special Purpose
Roads (Kenya Roads Board, 2012), though a definition of each road category is not provided. In addition
to classified roads, there are also unclassified roads that in the case of Kenya include Urban Roads,
Rural Roads and Tracks, National Park & Reserve Roads and Forest Roads. Rural Roads and Tracks
cover 110,000 kilometres and classified roads 63,291 kilometres (Ibid.).
For Tanzania, a distinction between classified and unclassified roads is not made (Roads Fund Board,
2012). However, the figure presented by the Roads Fund Board (which is practically the same as the
figure of the World Bank), refers solely to national and district roads – from trunk roads up to roads
leading to villages. This observation, and the fact that the total length is even smaller than the total length
of classified roads in Kenya, suggests that rural roads and tracks have not included in the calculation. For
a third check, the road network of South Africa was taken. According to the World Bank, this country has
a network of over 362,000 kilometres. This is in sharp contrast with a country like Kenya for instance, also
taking into consideration that it is only half the size of South Africa. Though this can partly be explained by
the fact that South Africa has invested more in its road network, such a high figure also suggest that more
roads, including those located in rural areas, have been classified. However, in the absence of data to
corroborate this hypothesis, the ratio (Unclassified) Rural Roads and Track / Classified Roads in Kenya
(110,000 kilometres / 63,291 kilometres or 1.74 / 1) was taken to estimate the length of unclassified roads
for the other countries in sub-Saharan Africa. The sum of classified and (estimated) unclassified rural
roads for each country was the basis for further calculations.
Subsequently, the length of the roads in each of the three types of dryland was calculated by using the
population density in each of these areas as a proxy (assuming a correlation of 100% between population
density and road density), in order to provide a more accurate estimate than using only the road density
of each country as a whole. This was not based on scientific evidence, yet under the assumption that
inhabited zones have a denser road infrastructure than less inhabited zones (e.g. deserts). Data on the
population size in the dryland areas were taken from Murray et al. (1999).
Next, a distinction was made between the rangelands and the cultivated lands that make up drylands for
the most part. Rangelands are characterised by (a combination of) nomadic/transhumant pastoralism,
sedentary livestock raising and/or cattle and sheep ranching (FAO, 1993). Cultivated lands include areas
where rainfed and irrigated agriculture is practiced (Ibid.). In the absence of data
23
Table 6. Proportion of rangelands, cultivated lands, urban areas and other areas in the drylands of the world
Rangelands
2
Area (km )
Dry subhumid
Semiarid
Cultivated
2
Share Area (km )
Urban
Totals
Others
2
Share Area (km )
2
Share Area (km )
2
Share Area (km )
Share
4.344.897
34%
6.096.558
47%
457.851
4%
1.971.907
15% 12.871.213 100%
12.170.274
54%
7.992.020
35%
556.515
2%
1.871.146
8% 22.589.955 100%
Arid
13.629.625
87%
1.059.648
7%
152.447
1%
822.075
5% 15.663.795 100%
Total dryland
30.144.796
59%
15.148.226
30%
1.166.813
2%
4.665.128
9% 51.124.963 100%
Source: adapted from MEA (2005: table 22.2)
regarding (sub-Saharan) Africa specifically, the share of the two land use types at the global level was
used: worldwide, rangelands occupy on average 59% of the drylands, while cultivated lands make up
30% (Millenium Ecosystem Assessment, 2005; see Table 6). In rangelands, road runoff harvesting is
suitable for pastoralists, while in cultivated lands the technology can be used for crop production by
farmers. The estimates are likely not very accurate for each individual country; however, this assessment
is primarily intended to provide a picture of the potential of using the road infrastructure for road runoff
harvesting in sub-Saharan Africa as a whole.
The next step consisted in estimating 1) the surface area of the roads that could be used for collecting
road runoff, and 2) the number of culverts that is present and that could be used for road runoff
harvesting (in both rangelands and cultivated lands) . The latter was done based on numbers published
by Jungerius et al. (2003) and Mati (1993), who reported an average of 0.57 and 2.1 culverts per
kilometre on road stretches of 42 and 149 kilometres, respectively. Due to a lack of information regarding
the culvert ‘density’ in other parts of Africa, it was decided to use a range of 0.25 and 2 culverts per
kilometre. Furthermore, only 25% of these culverts were assumed to be suitable for road runoff
harvesting, taking into account that they may not be located in the proximity of a farm, that the topography
does not allow for water harvesting (high slopes), that a gully has already formed making runoff
harvesting impossible, as well as possible other factors. Mati (1993), for instance, reports that 68% of the
culverts were found to discharge on slope steeper than 10% with severe erosion as result.
Regarding the surface area of the roads, a conservative width range of 5 to 10 meters was used based
on a broad approximation, which incorporates the roadside that also contributes to the amount of runoff.
At the same time, it was assumed that the whole road width can be used to collect runoff. Though this is
far from accurate, it does correct for additional runoff that is generally harvested from roadsides.
Moreover, 75% of the roads was assumed not to be suitable for road runoff harvesting, taking into
account areas with slopes of 0% or over 5%, the absence of farmland in the proximity of the road, areas
in the drylands that receive extremely low annual rainfall and possible other factors.
The total runoff volume that could be harvested with roadside drains was estimated using an average
annual rainfall of 300 mm, which according to the FAO classification (see Table 5) corresponds to the
upper range of the arid zones in Africa. A runoff coefficient of 0.2 and an efficiency factor of 0.5 were
applied for conservative estimates of runoff volumes, considering that more than half of the roads are
rural, unpaved roads. (In fact, part of the road network in sub-Saharan Africa is paved, which means that
for these roads runoff coefficients could be around 0.9, the share of paved classified roads varies per
country and is generally far below 50%; see World Bank (2012)).
The total runoff volume that culverts could collect was based on an estimated average catchment area of
1 hectare, more or less in line with the size of the catchment area of Mr Muindu Musyoka (Mutunga and
Critchley, 2001; see also Case study 1 in Chapter 4) but also taking into account the necessarily much
larger catchment area in the Tanzanian example from Hatibu et al. (2000).
24
Based on the assumption that no crop production takes place in rangelands, only the road surface in the
cultivated lands was deemed suitable for runoff harvesting with the intention to use the water for farming
purposes. To determine the potential size of the total cultivation area, a catchment/cultivation area ratio of
2/1 was used.
For both rangelands and cultivated lands the number of households that could potentially benefit from
road runoff harvesting was calculated. This was based on the following assumptions:
-
One culvert can benefit one farmer household in the cultivated lands (as in the case of Muindu
Musyoka)
One culvert can benefit at least one pastoralist household, i.e. one pan or dam can provide water
for their livestock (not based on scientific estimates)
An average of 500 m of road is used for road runoff harvesting both in rangelands and in
cultivated lands (considering the example of Muindu Musyoka as well as the examples from
banana growers in Uganda, that use smaller stretches of road (Ngigi, 2003a))
Lastly, the average size of a household in sub-Saharan Africa of 5.3 people (Bongaart, 2001) was taken
to give an estimate of the total number of people who could benefit from road runoff harvesting.
Table 7 summarises the assumptions that were made to perform the overall assessment.
25
Table 7. Summary of assumptions made to determine the potential for up-scaling road runoff harvesting
Assumption
Explanation
1.
Total length of rural roads is sum
of classified (World Bank figures)
and unclassified rural roads, and
length of unclassified roads can
be estimated by multiplying the
length of classified roads by 1.74
The figures by the World Bank (2012) only cover ‘classified’
roads The examples from Kenya and Tanzania indicate that a
large part of the road network is ‘unclassified’ and is not
represented byt he World Bank figures. The rural road network
in Kenya is 1.74 times the length of the classified network.
2.
Road density is (fully) correlated
with population density
As deserts generally have lower road densities than more
densily populated areas, the known population densities in arid,
semi-arid and dry sub-humid areas of sub-Saharan African
(Murray et al., 1999) were used to estimate the road densities of
these areas for each country.
3.
Cultivated lands and rangelands
make up 30 and 59% of drylands
(respectively) and this amount of
land cover is spread equally over
all countries and regions.
Country specific information on the occurrence of cultivated
lands and rangelands in the drylands of sub-Saharan Africa was
not available. For this reason, the global figures reported by
Millenium Ecosystem Assessment (2005) have been taken as a
basis.
4.
Cultivated lands are only rainfed
(no land is irrigated)
Less than 5% of the agricultural land in Africa is irrigated.
5.
Between 0.25 and 2 culverts can
be found on a random stretch of
1 kilometre of road
This range is based on the numbers reported by Jungerius et al.
(2003) and Mati (1993), who reported an average of 0.47 and
2.1 culverts per kilometre
6.
Roads (plus roadsides) have a
width of 5 to 10 metre
This is a broad approximation based on the limited data
available.
7.
25% of both culverts and
road(side) surfaces are suitable
for road road runoff harvesting
This is a rough estimate that takes into account unsuitable
topography, unsuitable location of farms, unsuitable local
climatic conditions and other potential factors limiting the use of
road runoff harvesting
8.
Average annual rainfall depth is
300 mm across the drylands
Conservative estimate based on lower range of rainfall depth in
semi-arid areas
9.
Runoff coefficient (K) is 0.2 and
efficiency factor (E) is 0.5
For reasons of simplicity, the same runoff efficiency factors were
used for estimating the runoff from both culverts and road
surfaces
10. Average catchment size for
culverts is 1 hectare
Conservative estimate based on the estimated size of the culvert
catchment of Muindu Musyoka (first case study, approximately
2 ha)
11. 1 household can benefit from 1
(suitable) culvert
Conservative estimate. Hatibu et al. (2000) show that more
households can benefit from large culverts
12. 1 household can benefit from a
stretch of 500 m of road (with an
estimated average width of 7.5
metre)
Conservative estimate based on the estimated length of the road
used by Muindu Musyoka.
13. 1 household consists on average
of 5.3 persons
Estimate based on average household size in sub-Saharan
Africa calculated by Bongaarts (2001)
26
4. Results
4.1 Case study 1: Muindu Musyoka
General description
Name of farmer:
Mr Muindu Musyoka
Location:
Kenya, Mwingi District, Kyethani Location, Mbondoni village (10 km west of Mwingi
town) Coordinates: (-0.978941, 37.987897)
Annual rainfall:
250 to 500 mm
Visited:
9 - 13 May 2011
WOCAT code:
KEN 022 b ; not yet recorded in the WOCAT system
The farm (or shamba) of Muindu Musyoka is located 10 km from Mwingi town. This 83 year old farmer
has been cultivating his land since 1952. Only in 1992 he started tapping runoff from a culvert that runs
under a nearby road – the one-lane motorway that leads eastwards from Nairobi, through Mwingi town to
the city of Garissa. Later, Musyoka also constructed fanya chini and fanya juu terraces: the first were
created by digging channels and throwing the soil downhill, the latter by throwing the soil uphill.
Schematically, his road runoff system looks like Figure 8.
His water harvesting technique was first described in 2000 with the WOCAT Questionnaire for SLM
Technologies (Mutunga and Critchley, 2001; the WOCAT questionnaire code is: KEN 022). Mutunga and
Critchley (2001) also mention that the technology was reported earlier by Mwarasomba and Mutunga as
early as 1995.
Figure 8. Schematic depiction of runoff flows on Muindu Musyoka’s farm
Schematic drawing of the farm of Muindu Musyoka. The blue arrows points in the direction of the water flow, that
starts left of the main road (a.) and is guided via a fanya chini channel (dotted line) in a neighbouring field (b.) to the
fanya chini and fanya juu (striped lines) terraces on his farm land. The schoolyard and a small road leading to his
farm further contribute to the amount of runoff that enters the farm land.
27
Technical performance
Conditions:
Annual rainfall varies between 250 and 500 mm according to the farmer. There
are two growing seasons: from March to the middle of May, and from October to
December. The farm is located at an altitude of around 1200 m above sea level.
The savannah-like environment is hilly with slopes between 2 and 5%. The soil is
20-80 cm deep with a sandy to loamy texture; the soil is moderately fertile and
contains little organic matter. Drainage is relatively good; the water storage
capacity of the ground is considered moderately good by the farmer. It is not clear
at what level the water table lies – it has likely sunk due to the recent dry years.
The 23 meter deep well on the farm’s courtyard was empty during the visit. There
is no surface water.
Purpose:
The reason for using road runoff harvesting is the lack of water for growing crops.
The land is primarily used for crop production. Musyoka also has some goats and
chicken that are fed with fodder from the land. The general purpose of this road
runoff harvesting system in combination with terraces is to enhance soil and
water conservation for improved crop production.
Measures:
The first structural measures that were taken are the channel that leads from the
culvert to the field, as well as small bunds across the road that guide the runoff
towards the entry of the culvert. This was done entirely by the farmer himself. In
addition, the farmer also uses the runoff that comes from two small roads that
lead to his farm as well, one of which is connected to a schoolyard (property of
his sister). For this purpose, he has adjusted the drains along the side of these
roads (see Figure 9)
Figure 9. Pictures of Muindu Musyoka showing how runoff is redirected to his farm
The picture on the left shows Muindu Musyoka pointing out the fanya chini channel that diverts the runoff from the
culvert (where the farmer is standing) to his field. The picture on the right shows Mr Musyoka explaining how the
runoff is guided from the schoolyard to his field (in the back).
28
Figure 10. Schematic overview of the terraces of Muindu Musyoka
The figure shows the dimensions of the fanya juu and fanya chini terraces. The space between the channels is
approximately 18 meters (or 60 feet).
The fanya chini and fanya juu terraces – structural measures – have been added
to improve the distribution of the road runoff, and at the same time to prevent
surface soil erosion, soil fertility loss and the loss of runoff. The terrace channels
are 2 feet deep and 3 feet wide with bunds (juu or chini) of 1.5 foot high and 4
feet wide. The distance between the channels is approximately 18 m (see Figure
10). Due to the terraces, water is given the time to infiltrate the soil and as the
slope of the terraces slowly decreases every year, more fertile soil is conserved
4
in the cultivation area. The terraces are fortified with grass (species unknown ;
vegetative measure). Management measures consist of controlling the inlets to
the terrace channels during showers in order to ensure a good distribution of the
water.
In the channels Musyoka grows maize, bananas, mango, sugar cane and
cassava. On the bunds he cultivates beans and on the terraces he grows maize
and beans.
The catchment area is the sum of area adjacent to the main road that leads to the
culverts and the area represented by the small roads and schoolyard (see Figure
2
11). The total surface of the catchment area was estimated at 65,000 m (6,5
hectares) with an average slope of approximately 3%. The average runoff
coefficient (K) was roughly estimated to be 0.3, taking into account the sandy soil,
slope and vegetation. The design rainfall (Pd) for one season was set at 200 mm
(considering an annual rainfall of 250-500 mm). Taken an efficiency factor (E) of
0.7, the amount of water that could be harvested can be calculated:
4
Probably Napier grass or Makarikari grass (Ngigi, 2003: 216).
29
2
Water Harvested = 65,000 m * 200 mm * 0.2 * 0.7 = 1820 m
3
The size of Musyoka’s cultivation area (see Figure 11) was estimated at 60,000
2
m (6 ha). The actual catchment : cultivation area ratio is thus 65,000/60,000 or
1.1/1. The crop water requirement (ETc) for one growing seasons was estimated
based on the two main crops of Musyoka, i.e. for beans (400 mm) and maize
(650 mm) following the FAO Irrigation Water Management Training Manual No. 3
(FAO, 1986), and thus estimated at an average 475 mm for the long season. The
required minimum catchment/cultivation area ratio would therefore be:
Required C/CA ratio = (475 – 200) / (200 * 0.3 * 0.7) = 275 / 42 ~ 6,5/1
2
With such a ratio the ideal cultivation area would be 3,800 m (0.38 ha). This
estimate is much smaller than the actual size of Musyoka’s farmland.
Knowledge required:
For the road runoff harvesting it not necessary to have a strong technical skills.
Just like the farmer did, this can be done on a trial and error basis. For the
terraces, no skilled labour is needed. However, to define the types of terraces
and the distance between the channels, farmers may need the advice from an
extension worker.
Figure 11. Catchment and cultivation area of Muindu Musyoka highlighted on a satellite image
Google Earth image of Musyoka’s farm land (indicated in green), his homestead (yellow pointer) and the estimated
catchment indicated in blue.
30
Economic viability
Conditions:
The farmers living in this area are all relatively poor. Off-farm income is important
for Musyoka, who has grandchildren working in the city that send him money. The
wife of one of his sons works in a shop in town and also provides money to the
family. Farming is done for subsistence and for cash crops (maize and beans).
Seasonal cropping is combined with the cultivation of fruit trees (agroforestry).
Access to the market (and possibly also government employees and extension
workers) is relatively easy since Mwingi town is only 10 km away. Ploughing is
done by hand or with help of a zebu oxen. There is no other source of water than
rain; rainwater is also collected on the roofs of his homestead and stored in one
(leaking) concrete tank. This water is used for household purposes only.
Costs:
Construction of the road runoff harvesting system was done by Musyoka himself.
The costs of hiring day workers to construct the fanya chini and fanya juu
terraces from August to October 1996 (3 months) – just before the rainy season –
5
were US$ 471 . Musyoka had to borough some money from his family members
to pay for this. In 2009 he spent approximately US$ 30 on day workers for the
maintenance of the channels. The maintenance costs become higher every year.
The costs of agricultural input (seeds and fertiliser) are not known.
Benefits:
According to the farmer, the yields are 20 to 50% higher and the risk of failure is
much smaller. Income increases with 20-50% with the sales of maize and beans.
He needs 5-20% less fertiliser. However, the last year in which he sold bags of
maize or beans was 2007. Table 8 shows the data on yields and sales that
Musyoka recalls. He does not know in detail what he produced before 2007. In
the period 2004-2006 his yields were low; in 2003 they were somewhat better.
2002 was a good year, while yields in 2000-2001 were similar to 2003. It is
interesting to see that from 2007 no yields have been recorded – though it has
not been possible to support this information via another independent source.
During productive rainy seasons, there is less need to produce sisal ropes
(kamba – the reason why the tribe is called the Kamba) for sale on the local
market.
The benefits, both on the short and the long term, outweigh the establishment
and maintenance costs – provided, however, there is enough rain.
Disadvantages:
The main disadvantage is that water is the limiting factor. As long as there is (not
enough) rain, production is impossible.
Labour for establishment and maintenance of the structures is the most
expensive factor.
5
st
For each amount of money, the exchange rate on the 1 of January of the corresponding year (in this case 1993)
was used to convert KSh. to US$.
31
Table 8. Yields and sales of Muindu Musyoka during the period 1998-2011
Year
Season
Maize yield
Beans yield
1998-2006
Both seasons
Varying
yields
Varying
yields
March - May
1350 kg
540 kg
October- December
1530 kg
180 kg
Both seasons
0
0
2007
2008-2011
Sales (and further remarks)
•
No data
•
450 kg maize sold US$ 39
•
•
630 kg maize sold for US$ 81
(450 kg of maize destroyed by
Osama weevil )
•
No sales
Timeline showing the yields and sales of maize and bean of Musyoka. Produce that was not sold or lost to weevils
was used for subsistence purposes of the farmer and his family.
Environmental friendliness
Conditions:
Musyoka’s farm is surrounded mostly by farmland used by other farmers for
cultivation. It is a savannah like environment with limited biodiversity (wild
mammals, birds and insects like butterflies were very rare during the time of visit).
Benefits:
The increase in production during the productive rainy season ensures a wider
ground cover, which results in a higher above and underground biomass and
adds to a higher biodiversity at the surface and in the soil. The farmer also has
the impression that evaporation from the soil surface decreased, as well as its
salinity.
Disadvantages:
Musyoka is not aware of any negative (downstream) impacts on the environment.
Nevertheless, due to the fact that the water is collected from a tarmac road, there
is a risk of some oil, rubber or other pollution. This may however partly be filtered
out in the catchment area and in the channel leading to his farm.
Social acceptance
Conditions:
The Technique is applied by one man from a single (large) household. Ploughing
is done by hand or with animal traction. The land is the property of Musyoka; he
has all land and water use rights. Population density is between 10-50 people per
square kilometre. There are no data on annual population growth in the region.
Origin:
The idea of starting road runoff harvesting comes from Musyoka himself, though
he also received some advice from the Ministry of Agriculture and Rural
Development according to Mutunga and Critchley (2001).
Benefits:
The farmer’s large family benefits from the production in times of rain. Other
farmers have benefited from the Musyoka’s knowledge of soil and water
conservation techniques: in the period from 1999 until 2007 he hosted up to 10 (!)
group visits per month. (In total, around 800 farmers have been brought by
Promoting Farmer Innovation (PFI) to his farm according to Mutunga and
Critchley (2001))
32
Disadvantages:
Musyoka is not aware of consequences for his downstream neighbour. However,
in the upstream catchment area, he has a small dispute with his sister who owns
the land through which the channel runs that links the culvert to his land (William
Critchley, pers. comm.).
Another negative impact is the fact that some farmers living in the area have
become annoyed with the attention Musyoka has received as a ‘model farmer’
over the years from government employees and researchers alike (Ibid.).
Adoption:
Probably thanks to the training courses that the farmer organised on his farm, 8
other farmers in the area have adopted road runoff harvesting according to
Musyoka.
Figure 12. Muindu Musyoka showing dried maize in a calabash at his homestead
33
4.2 Case study 2: Mwema Maswili
General description
Name of farmer:
Mr Mwema Maswili
Location (coordinates):
Kenya, Mwala District, Jathui County, 1 km northeast of Wamunyu town (1.413974, 37.625281)
Annual rainfall:
250 to 750 mm
Visited:
18 May 2011
WOCAT code:
Not yet recorded in the WOCAT system
It is the first time that this farm has been described with the WOCAT Questionnaire for SLM
Technologies. The road runoff harvesting system has been set up by Mwema Maswili in 1998. The
system is based on a roadside drain along a dust road that runs of which the runoff is guided through a
fanya chini ditch and an old gully to a pond located at the bottom of his field (see schematic drawing in
Figure 13). Just like Muindu Musyoka (Case study 1), he has added fanya juu terraces to his farm later
on. They were built along the contour lines with technical support from peace workers in 2005.
Figure 13. Schematic overview of the Mwema Maswili’s farm
Runoff is collected from the road and guided through a fanya chini ditch across his farm into a pond. Arrows indicate
the direction of the runoff flow.
34
Technical performance
Conditions:
Maswili says annual rainfall varies between 250 and 750 mm. There are two
growing seasons: a short season from March until the middle of May, and a
longer season from October to December. The shamba lies between 1260 and
1275 m above sea level. Slopes in the area vary between 2 and 5%.The soil has
limited fertility, is 120 cm deep and its texture is sandy to loamy. Natural drainage
is considered sufficient. It is not clear what the ground water level is, though it is
likely very low, because drinking water comes from the river and is available from
a tap at a neighbouring farm – there is no well in use for this.
Purpose:
The technical purpose of the system is first to increase water availability for
supplementary irrigation of crops and fruit trees. Second, the terraces have been
constructed to harness the rainwater that falls in situ.
The reasons for the land degradation were water and wind erosion, loss of
topsoil, gully erosion, and compaction by people walking over the unterraced
field.
Measures:
The structural measures consist of a roadside drain running along the side of Mr
Maswili’s farm, which leads via a drain along the path leading to his courtyard to a
fanya chini channel that transects his shamba (see Figure 14); subsequently, the
water runs into an old gully (!) which ends up in a pond. The pond was
constructed with help of day workers and has a concrete wall on the downhill side
(see Figure 15). The pond is 10 m wide, 20 m long and 2.5 m deep which
3
corresponds to a volume of 500 m . The pond has a spillway in the corner
opposite of the inlet – this spillway leads into a short fanya chini channel. At first,
water was drawn from the pond with a small diesel pump; later the farmer took
water with a jerry can. Other structural measures are the fanya juu terraces. On
the bunds of the terraces Napier grass has been planted as a vegetative
measure. The only management measure is the fact that people are not allowed
to walk over the field anymore.
Figure 14. Roadside drain and fanya chini channel on the farm of Mwema Maswili
The picture on the left shows Maswili (holding his two children) next to the roadside drain that runs along his field. On
the right Ms Rose Mueni (interpreter) shows the channel that transects Maswili’s farm and directs road runoff to the
pond.
35
Figure 15. Pond of Mwema Maswili
The white arrow shows the direction of the water flow at the inlet of the pond. The farmland is located on the right
side (uphill). The picture clearly shows that only one side (downhill) of the pond is fortified with a concrete wall.
Crops (80%) and fruits trees (20%) on the lower three terraces (0.2 ha) are
provided with water through supplementary irrigation (1 jerry can of water every
second day for each tree). On these terraces he grows maize and beans as well
as mango, lemon, pawpaw and guava tress (approximately 100 in total). On the
other terraces uphill, which are only rainfed, the farmers grows maize, beans and
pigeon peas.
The roadside drain was dug by the farmer and his son. The pond was dug bit by
bit from 1998 onwards by the farmer, his son and additional day workers, for a
period of 3-4 years. The fanya juu terraces were built by day-workers in 2005.
The pond has cracks in the floor and water is lost through the porous stone on
which it is built. It would require lining to prevent it from leaking.
The catchment area is formed by the dust road and a number of paths uphill that
2
lead onto this road. The surface area is roughly estimated at 10,000 m (1 ha).
The runoff coefficient is estimated at 0.4, taking an average slope of around 3%,
a sandy soil and no vegetation. The design rainfall (Pd) for the second, long
season of the year was estimated at 300 mm (considering an annual rainfall of
250-750 mm). Taken an efficiency factor (E) of 0.7, the potential amount of runoff
was calculated as follows:
2
Water Harvested = 10,000 m * 300 mm * 0.4 * 0.7 = 840 m
3
2
The size of Maswili’s cultivation area was estimated at 6,000 m (0.6 ha; only on
the lower part of his land supplemental irrigation is used). The actual catchment :
cultivation area ratio is thus 10,000/6,000 or 1.7/1. The crop water requirement
(ETc) was estimated at 500 mm for one season, based on the average for maize
and beans and the amount that fruit trees use, which varies between 300 and 800
mm. The minimum catchment/cultivation area ratio would therefore be:
36
Required C/CA ratio = (500 – 300) / (300 * 0.4 * 0.7) = ~ 2.4/1
With such a ratio the ideal cultivation area would be approximately 0.4 ha. This
comes close to the 0.6 ha which Maswili uses.
Knowledge required:
Little knowledge is required for diverting the road runoff in the field. With
inventiveness, the farmer has constructed a fanya chini channel and incorporated
an existing gully in the system.
More difficult is the creation of a pond that is well-lined and that has proper inand outlets and a water pump.
The fanya juu terraces require some knowledge about the right sizes of channel
and distance between the channels. This knowledge is generally available at the
local government post (extension workers).
Economic viability
Conditions:
The farmers living in this area are all relatively poor. Off-farm income becomes
more important in times of drought. Maswili sells small animal statues carved out
of wood. Another source of income is the selling of water from his pond to
farmers in the area (the last time was in 2006). The farmer has also started
keeping bees for the production of honey that has a high economic value.
Farming is done for subsistence and for cash crops (maize, beans and fruits).
The market that is closest by is about 1 km away in Wamunyu town. Extension
workers are active in the area. Ploughing is done with cows. Besides rainwater,
the farmer also buys water at a neighbouring farm when needed; this water
comes from a nearby river. Maswili collects rainwater from the roofs of the
building on his compounds, which is stored in tanks for domestic use.
Costs:
Establishment of the pond cost US$ 1,260 to pay day workers over a period of
around 300 days. They were paid for digging 114 ‘spaces’ (each 24 feet long, 3
feet wide, 2 feet deep), each worth US$ 11. Costs were entirely born by the
farmer.
Establishment of terraces (approximately 500 m of fanya juu terraces) cost US$
173 in 2005.
The maintenance activities include the re-excavation of the roadside drain in
2011, by two labourers (among whom his assistant), which took 3 full time days
for a total cost of US$ 18. Re-excavation of the fanya juu channels by labourers
cost US$ 35.
The farmer also hires people to water the trees: one man is paid US$ 1.7 per day,
and another man is hired on a continuous basis for US$ 35 per month.
Maswili’s wife spends 2-3 days planting seeds and seedlings: 10 kg beans (US$
12), 6 kg maize (US$ 17) and 1 package of sukuma seedlings (very cheap) and 2
kg cowpeas every two seasons (US$ 1.20).
Benefits:
In 1998 the maize yield was 270 kg (3 bags); in 2010 he obtained a yield of 1890
kg (21 bags), of which he sold 10 bags for in total US$ 260 and kept 11 bags for
his family. Due to increase in fodder production he also increased the number of
cows from 2 in 1998 to 6 in 2010. He uses the manure of his livestock to fertilise
37
the land, thereby decreasing the need to buy fertiliser. Because of the recent
drought has had to sell some of his livestock.
The rainwater harvesting system has allowed him to starting growing fruit trees.
Last season (February 2011), he earned US$ 123 from selling mangos from his
mango trees (a normal yield is gives US$ 74). The variety of agricultural products
has increased since he started collecting road runoff.
Labour constraints and workload have decreased slightly. This has allowed him
to invest some time and money in the production of honey (since 2007).
When rainfall is sufficient, the farmer sells the excess water in the pond to his
neighbours: in January and February 2006, he earned $ 111.
The farmer is very positive about the short and long term benefits of his soil and
water conservation measures, taking into account both the investments for
establishment and maintenance of the structures.
Disadvantages:
The farm pond has cracks in the floors and water seeps through the porous
stone. It would cost about US$ 980 to line the pond. Adding the costs for the
necessary extra digging, the total expenditure would amount to around US$
1,200. Mr Maswili is nonetheless very interested, especially in setting up a
greenhouse close to his pond (see case study D), which would allow the fast
recuperation of the investment costs.
Environmental friendliness
Conditions:
The savannah-like environment showed little sign of a rich fauna. The area
located downhill from Maswili’s land is rangeland.
Benefits:
One of the benefits from this system is that the farmer has been able to start
beekeeping, which represents both an increase in fauna as well as in the
provision of an ecosystem service: pollination.
The increase in the varieties of fruit trees has led to a richer agrobiodiversity. The
natural fertiliser from the livestock has likely made the soil more rich in carbon
and in soil biodiversity.
It is not clear whether the increase in runoff downhill has benefited the flora and
fauna on the bare land that is located in the downstream area next to Maswili’s
shamba.
Disadvantages:
The farmer is not aware of any negative impacts on the environment.
38
Social acceptance
Conditions:
Population density is between 10-50 people per square kilometre. Data on annual
population growth in the region were not found. Land and water use rights belong
to the farmer. Manual labour and animal traction are used to cultivate the land.
Maswili does not know of other farmers in the area using road runoff harvesting.
Origin:
Road runoff harvesting is an invention of Maswili. For the construction of the
fanya juu terraces, the farmer followed the example of his neighbour Mr Mulei
Ndolo and asked peace workers for advice on how to construct them.
Benefits:
In times of rain, the pond is a source of water also for other people. The
pollination service provided by the honey bees also benefits other farmers in the
area. Because of the prior investment and the subsequently increased
production, the farmer has been able to provide jobs to day workers and a fixed
employee. His increased purchasing power (he bought extra cows for instance)
was also good for the local economy.
Disadvantages:
Social disadvantages are not known.
Adoption:
The farmer says no other farmers have adopted road runoff harvesting. His
neighbour, he says, is “too lazy” to invest in it.
39
4.3 Four other sites in Machakos District
Farm of Samuel Mweu Maingi (site #3)
Location (coordinates):
Kenya, Machakos District, a few kilometres from Masii town (-1.46092,
37.439492)
Visited:
17 May 2011
The owner of the farm is Mr Samuel Maingi (64 years old and an old chief). The road runoff harvesting
system is done with roadside drains from small sandy roads, a pond and a rope-and-washer pump for
irrigation of four fanya juu terraces (see Figure 16). Runoff from the road flanking is led into a parallel
within-field channel through mitre. This channels directs the runoff into a pond. Before entering the pond,
6
the water passed through a small silt trap which lets the water into the pond .
The pond was established in 2004, yet there are no data regarding the total establishment and
maintenance costs. The pond is approximately 5 m wide, 10 m long and 4 m deep and has a total
3
volume of approximately 200 m . It is lined with 0.8 cm thick, high quality polythene that cost US$ 4.75
2
per m in Nairobi; total costs of lining were approximately US$ 570. The pond was constructed over a
period of one year in 2004. The lining has a ten year guarantee and still hasn’t shown any leakages.
There is a separate overflow pipe on the downhill side.
His harvests fail because of insufficient amounts of rainwater or because of (previous) leakage from the
ponds. According to Samuel Maingi, the payback time is only 3 years.
According to Maingi, one shower is enough to fill the entire pond. He pumps the water with a simple rope7
and-washer pump up to four terrace levels or 3 metre higher and irrigates approximately 0.8 ha with the
harvested water.
The farmer grows sukuma, maize, cabbages, onions, tomatoes, papayas, mangos, sweet potatoes,
‘sweet peppers’, eggplants, cowpeas, chickpeas. He uses fertilizer and manure. He hired an extension
worker to make the planning profile for the season that started in October 2011.
This road runoff harvesting approach has been adopted by at least two farmers as far as Maingi is aware.
However, these farmers used local, thinner and less expensive lining of the pond that is less resistant.
6
According to Alex Oduor (ICRAF), who joined the visit, a T or Y junction just before the silt trap would be better, as it
would allow water to leave the pond from the same side, which prevents sedimentation in the pond.
7
It would be beneficial to use a rope-and-washer pump with two pulleys instead of one (see Malesu et al. 2007), this
would allow the farmer to get the water as high as the upper terrace in one effort. The current pump can be made
more efficient by adding a larger bowl on top of the pump (where the water comes out and flows into the irrigation
pipe), to prevent water loss when it is pumped to fast.
40
a. Farm of Samuel Maingi (site #3)
b. Farm of a neighbour of Samuel
Maingi (site #4)
c. Farm of David Kyula (site #5)
Figure 16. Schematic overview of three of the four additional farms
The three drawing (a., b. and c.) correspond to the farms of Samuel Maingi, his neighbour and David Kyula
(respectively).
). No schematic overview of Mr. Sammy’s farm (site #6) was made. Arrows indicate the direction of the
runoff.
41
Farm of a neighbour of Samuel Maingi (site #4)
Location (coordinates):
Kenya, Machakos District, a few kilometres from Masii town (-1.46092,
37.439492)
Visited:
17 May 2011
The name of this farmer was not mentioned by Mr Samuel Maingi. The farmer uses a lined pond in
combination with a greenhouse that was paid for and is managed by a group of farmers called ‘Mango
Integrated’, to which Maingi also belongs. Structural measures are the roadside drains that are combined
with a silt trap, a lined pond, a treadle pump, an elevated (foldable) tank and a greenhouse with drip
irrigation system. The pond is ´fed´ with runoff from a roadside drain and from channel that probably
collects water from the same road (see Figure 16). Maintenance of the pond is carried out by people who
were trained in 2004 by RELMA-in-ICRAF.
The greenhouse is provided by Amiran Ltd. as a ‘package’ together with treadle pump, tubes for drip
irrigation (for growing tomatoes), and an easily transportable water tank (made of synthetic material that
8
can be folded) . A complete greenhouse package (tent, tank, pipes, and training during the first season)
costs US$ 1,800-2,500. Tomatoes are the main crop produced in the greenhouses; yields can amount to
6-8 ton per ha. According to Mr Peter Kamau (the local agricultural extension officer) the payback time is
just one season.
The greenhouse and drip-irrigation system is part of an initiative of World Vision International (WVI), a
Christian development organization from the USA, and two other partners: Amiran Kenya Ltd and Mwala
IPA. According to Mr Frank Meme (pers. comm.), Mwala IPA provides loans to farmers who are
interested in adopting the package. Amiran Kenya Ltd. constructs the greenhouse systems and visits
each site on a monthly basis during the first 12 months to provide technical assistance. WVI further
assists farmers in Operation and Maintenance (O&M) of the system. The objective of this initiative is to
ensure food security and increase farmers’ incomes.
Twenty groups of farmers have thus far adopted this system, indicating a strong interest of farmers to
commonly engage in such a scheme. They grow tomatoes, capsicum, onions and other cash crops.
Nevertheless, there are many ponds in the area that are used for fish farming – which turns out to be little
profitable because of the low (local) demand, as the Kamba people do not have a habit of eating fish.
However, smallholder farmers are afraid of investing in a greenhouse and don’t want to count further than
one year ahead.
Farm of David Kyula (site #5)
Location (coordinates):
Kenya, Machakos District, a few kilometres from Mwala town
(-1.352017, 37.450258)
Visited:
18 May 2011
The farmer who developed this road runoff harvesting system is Mr David Kyula. The system combines
roadside drains and a small culvert to collect sheet runoff (see Figure 16). Annual rainfall is 400-1000 mm
according to the farmer, with sometimes 96 mm falling in one day.
Runoff is collected from a small dust road that runs uphill for about a kilometre. Part of the water also
passes through a small culvert under the convex road, after which it is led it via a large earthen silt trap
and a small silt trap into a large unlined pond. The large silt trip is a U-shaped dam made out of soil, that
8
See also http://www.amirankenya.com/
42
filters the water as the water can only leave on the same side where it also enters the trap. The pond is
3
40 m long, 25 m wide and 4 m deep and hence has a capacity of approximately 4000 m . Because the
pond is unlined, water seeps through the walls and creates the perfect environment for a vegetable
garden on one side (downhill). Because the pond is constructed uphill with respect to the culvitavation
area, it is easy to transport the water for supplementary irrigation: water is poured with a bucket in a
barrel that stand next to the pond, and that is connected to a hose that is used downhill to fill other barrels
or jerry cans that are used for the irrigation of maize. The water is used to irrigate approximately 2.83 ha
of land.
It took 14 men 3 months (full time) in 2004 to construct the pond. The total cost of US$ 2,700 were paid
by David Kyula himself.
Due to the seepage through the side of the pond, there is not only enough water for Kyula’s vegetable
garden, but also for the field with fruit trees that lies next to his land. His neighbor thus literally enjoys the
fruit of Kyula’s labour. The variety of plants and availability of surface water in this vegetable garden also
attracted insects like bees and butterflies.
It is not known whether other farmers in the area have adopted similar techniques.
Farm of Mr Sammy (site #6)
Location (coordinates):
Kenya, Machakos District, a few kilometres from Mwala town
Visited:
18 May 2011
This site belongs to a certain Mr Sammy and is managed by another man also known as Mr Sammy. No
schematic drawing was made of his site.
3
Road runoff is collected in a large underground tank of 95 m . It is pumped into two plastic tanks at a
height of approximately 2.5 m with a 2.5 hp petrol pump. The stored runoff is used mainly to provide
supplementary irrigation to mango and orange trees; maize and peas are mostly rainfed. The farmer has
also adopted a zero grazing policy.
Construction of the sophisticated water storage installation has cost more or less US$ 6,000. The farmer,
convinced of the benefits of rainwater harvesting, also collects rainwater from all his roofs for domestic
purposes.
(The farm also has a (Dutch) biogas installation in an underground tank covered with metal boards, which
was constructed by a contractor. The costs of US$ 430 were for a large part paid by the government
(US$ 345) and the rest by the farmer himself.)
43
4.4 Suitable roads and culverts in sub-Saharan Africa
Table 9 presents the estimated road network that is present in the drylands of sub-Sarahan Africa. Of the
estimated total 5.55 million kilometres of road, approximately half (2.65 million kilometres) are located in
the drylands. Of these the majority are located in the semi-arid areas (1.65 million kilometres), while only
a small part (ca. 210,000 kilometres) is found in the arid areas. An estimated 89% or 2.36 million
kilometres of the dryland roads are located in rangelands and cultivated lands. The length of the roads in
the drylands of each country was calculated by adjusting the average road density per country, assuming
that road density is positively correlated with population density. Without this adjustment, the estimated
total length in the drylands would be 11% higher.
Looking at all the rangelands and the cultivated lands of sub-Saharan Africa, the road networks have an
estimated length of around 1.57 and 0.80 million kilometres respectively.
At the country level, there are major differences. The countries located in the wet, tropical zones of subSaharan Africa (e.g. Congo, Gabon and Sierra Leone) have no drylands. Countries with (nearly) all roads
located in the drylands are, for instance, Botswana, Namibia and The Gambia. In Kenya (underlined in
Table 9), it is estimated that 36.6% of the roads can be found in the drylands, of which the majority can be
found in dry sub-humid and semi-arid zones (both around 29,000 kilometres) and a small part in the arid
lands (around 3,800 kilometres). Countries with the largest estimated dryland road networks are South
Africa, Zimbabwe, Burkina Faso and Nigeria.
In Table 10 results are shown which are based on estimated numbers of culverts that can be found under
dryland roads. For the rangelands, between 100,000 and 400,000 culverts in sub-Saharan Africa are
expected to be potentially suitable for runoff harvesting, while this number is estimated between 50,000
and 200,000 in the cultivated areas. The volume of runoff that these culverts can produce together is in
the range of 0.15 and 0.59 cubic kilometres. Assuming that only one household can exploit the runoff
from one culvert, a total of 370,000 households could benefit from the additional water. The highest
estimates can, logically, be found in the countries with the largest road networks. For Kenya (underlined
in Table 10), somewhere between 3,000 and 14,000 culverts could be suitable for runoff harvesting,
which could potentially benefit (an average of) 8,000 households.
The results of the assessment for the suitable road surface are presented in Table 11. In total, between
300,000 and 600,000 hectares of road surface may be available for runoff harvesting with roadside
drains. In the cultivated areas, some 75,000 hectares of land (taking the average of the lower and upper
range) could potentially be flooded or irrigated with the generated runoff (assuming a C/CA ratio of 2/1).
The estimated potential runoff volume that could be collected with roadside drains lies between 0.09 and
0.18 cubic kilometres. The (averaged) number of households that could benefit from the runoff collected
through roadside drains is 1.8 million. Looking at the Kenya for instance, around 41,000 households may
be able to collect road runoff. The potential cultivation area in Kenya’s cultivated lands would be around
1,700 ha.
Roughly estimated, a total of 2.2 million households could thus benefit from approximately 0.5 cubic
kilometre of road runoff. Assuming an average size of 5.3 persons per household (Bongaarts, 2001), 11.7
million people would be able to directly benefit from road runoff harvesting.
44
Table 9. Length of total road network in the drylands
Country*
Total
Total in
Share drylands In dry subroads
drylands
of total roads
humid
rural
rural
areas
km
km
km
km
In semiarid
areas
In arid
areas
In
In cultivated
rangelands land (30% of
(59% of
drylands)
drylands)
km
km
km
km
Angola
140,813
45,341
32.2%
11,104
33,559
678
26,751
13,602
Benin
52,022
4,822
9.3%
3,417
1,405
0
2,845
1,447
Botswana
70,635
70,635
100.0%
0
68,524
2,111
41,675
21,191
Burkina Faso
253,252
247,787
97.8%
51,458
192,411
3,917
146,194
74,336
Burundi
33,738
1,285
3.8%
1,285
0
0
758
385
Cameroon
79,011
17,706
22.4%
5,357
12,344
6
10,447
5,312
Cape Verde
3,696
3,581
96.9%
0
0
3,581
2,113
1,074
Central African Rep
66,553
1,020
1.5%
755
265
0
602
306
Chad
109,520
94,053
85.9%
32,442
37,898
23,712
55,491
28,216
Comoros**
2,409
0
0.0%
0
0
0
0
0
Congo
46,546
0
0.0%
0
0
0
0
0
Congo Dem Rep
420,275
9,277
2.2%
9,277
0
0
5,473
2,783
Cote d’Ivoire
224,505
0
0.0%
0
0
0
0
0
Djibouti
8,392
8,308
99.0%
0
14
8,294
4,902
2,492
Equatorial Guinea
7,885
0
0.0%
0
0
0
0
0
Eritrea
10,979
10,851
98.8%
0
7,989
2,862
6,402
3,255
Ethiopia
121,455
44,195
36.4%
21,838
16,601
5,756
26,075
13,259
Gabon
25,107
0
0.0%
0
0
0
0
0
Gambia The
10,246
10,246
100.0%
8,676
1,569
0
6,045
3,074
Ghana
299,852
42,371
14.1%
42,371
0
0
24,999
12,711
Guinea
121,425
694
0.6%
694
0
0
410
208
Guinea-Bissau
9,460
0
0.0%
0
0
0
0
0
Kenya
169,606
62,047
36.6%
29,199
29,093
3,756
36,608
18,614
Lesotho
16,264
11,873
73.0%
10,420
1,453
0
7,005
3,562
Liberia
29,023
0
0.0%
0
0
0
0
0
Madagascar
136,427
15,699
11.5%
3,792
11,907
0
9,262
4,710
Malawi
42,305
25,302
59.8%
23,837
1,466
0
14,928
7,591
Mali
61,534
58,925
95.8%
6,880
42,825
9,220
34,766
17,677
Mauritania
30,299
23,146
76.4%
0
2,893
20,253
13,656
6,944
Mauritius
5,657
0
0.0%
0
0
0
0
0
Mozambique
83,046
45,557
54.9%
31,362
14,195
0
26,879
13,667
Namibia
115,270
110,937
96.2%
0
93,008
17,929
65,453
33,281
Niger
51,880
50,949
98.2%
0
23,104
27,844
30,060
15,285
Nigeria
528,982
201,708
38.1%
45,513
152,363
3,831
119,008
60,512
Rwanda
38,354
2,797
7.3%
2,797
0
0
1,650
839
Sao Tome & Principe
876
0
0.0%
0
0
0
0
0
Senegal
40,591
36,702
90.4%
2,110
31,382
3,210
21,654
11,011
Sierra Leone
30,939
0
0.0%
0
0
0
0
0
Somalia
60,510
56,487
93.4%
0
21,232
35,255
33,327
16,946
South Africa
991,428
776,626
78.3%
153,338
599,129
24,160
458,209
232,988
Sudan
32,582
27,127
83.3%
1,858
12,076
13,193
16,005
8,138
Swaziland
9,840
6,614
67.2%
4,926
1,688
0
3,902
1,984
Tanzania
283,947
147,683
52.0%
95,715
51,968
0
87,133
44,305
Togo
31,903
9,979
31.3%
9,979
0
0
5,887
2,994
Uganda
193,703
20,940
10.8%
18,372
2,568
0
12,354
6,282
Zambia
182,847
95,562
52.3%
72,885
22,677
0
56,382
28,669
Zimbabwe
266,317
255,932
96.1%
95,704
159,895
333
151,000
76,780
TOTALS 5,551,908
2,654,766
797,359 1,647,504
209,903
1,566,312
796,430
% total rural roads:
47.8%
14.4%
29.7%
3.8%
28.2%
14.3%
*Not included are Seychelles and South Sudan; ** Comoros includes island of Mayotte. Sources: World Bank (2012), Murray et al.
(1999), Millenium Ecoystem Assessment (2005)
This table shows data on the length of the road network (in kilometres) in the drylands of sub-Saharan Africa. The total
length in the drylands is based on the estimates for dry sub-humid, semi-arid and arid arids, that are presented in the
shaded columns. Also indicated are the estimated lengths of roads located in rangelands and cultivated lands.
45
Table 10. Estimates per country of number of culverts, potential runoff volumes and number of households
that could benefit from road runoff
Culverts in rangelands Culverts in cultivated Total runoff volumes
Households
lands
Assumptions: Number
(0.25/km,
25%
suitable)
Country
Angola
Benin
Botswana
Burkina Faso
Burundi
Cameroon
Cape Verde
Central African Rep
Chad
Comoros*
Congo
Congo Dem Rep
Cote d’Ivoire
Djibouti
Equatorial Guinea
Eritrea
Ethiopia
Gabon
Gambia The
Ghana
Guinea
Guinea-Bissau
Kenya
Lesotho
Liberia
Madagascar
Malawi
Mali
Mauritania
Mauritius
Mozambique
Namibia
Niger
Nigeria
Rwanda
Sao Tome & Principe
Senegal
Sierra Leone
Somalia
South Africa
Sudan
Swaziland
Tanzania
Togo
Uganda
Zambia
Zimbabwe
TOTALS
Units
1,672
178
2,605
9,137
47
653
132
38
3,468
0
0
342
0
306
0
400
1,630
0
378
1,562
26
0
2,288
438
0
579
933
2,173
854
0
1,680
4,091
1,879
7,438
103
0
1,353
0
2,083
28,638
1,000
244
5,446
368
772
3,524
9,438
97.894
Number
(1/km, 25%
suitable)
Number
(0.25/km,
25%
suitable)
Number
(1/km, 25%
suitable)
Low estimates
High estimates
1 household per
culvert
Units
Units
Units
m3
m3
(number)
6,688
711
10,419
36,549
189
2,612
528
151
13,873
0
0
1,368
0
1,225
0
1,601
6,519
0
1,511
6,250
102
0
9,152
1,751
0
2,316
3,732
8,691
3,414
0
6,720
16,363
7,515
29,752
413
0
5,414
0
8,332
114,552
4,001
976
21,783
1,472
3,089
14,095
37,750
391.578
850
90
1,324
4,646
24
332
67
19
1,763
0
0
174
0
156
0
203
829
0
192
794
13
0
1,163
223
0
294
474
1,105
434
0
854
2,080
955
3,782
52
0
688
0
1,059
14,562
509
124
2,769
187
393
1,792
4,799
49.777
3,401
362
5,298
18,584
96
1,328
269
77
7,054
0
0
696
0
623
0
814
3,315
0
768
3,178
52
0
4,654
890
0
1,177
1,898
4,419
1,736
0
3,417
8,320
3,821
15,128
210
0
2,753
0
4,237
58,247
2,034
496
11,076
748
1,570
7,167
19,195
199.107
2,522,116
268,225
3,929,073
13,783,134
71,453
984,917
199,215
56,762
5,231,674
0
0
516,028
0
462,136
0
603,598
2,458,372
0
569,912
2,356,909
38,627
0
3,451,392
660,419
0
873,265
1,407,448
3,277,691
1,287,496
0
2,534,123
6,170,874
2,834,022
11,220,001
155,593
0
2,041,566
0
3,142,087
43,199,829
1,508,918
367,895
8,214,884
555,056
1,164,775
5,315,631
14,236,242
147.671.360
10,088,463
1,072,901
15,716,293
55,132,534
285,814
3,939,668
796,860
227,046
20,926,698
0
0
2,064,112
0
1,848,544
0
2,414,393
9,833,490
0
2,279,648
9,427,637
154,509
0
13,805,567
2,641,674
0
3,493,060
5,629,791
13,110,765
5,149,984
0
10,136,491
24,683,497
11,336,088
44,880,002
622,373
0
8,166,264
0
12,568,349
172,799,315
6,035,672
1,471,580
32,859,537
2,220,225
4,659,101
21,262,526
56,944,969
590.685.441
6,305
671
9,823
34,458
179
2,462
498
142
13,079
0
0
1,290
0
1,155
0
1,509
6,146
0
1,425
5,892
97
0
8,628
1,651
0
2,183
3,519
8,194
3,219
0
6,335
15,427
7,085
28,050
389
0
5,104
0
7,855
108,000
3,772
920
20,537
1,388
2,912
13,289
35,591
369.178
This table shows data on the estimated number of culverts in rangelands and cultivated lands, as well as the runoff volumes
that these could generate assuming a catchment area of 1 ha (see text for more information). The estimated (averaged)
number of households that could potentially benefit from road runoff harvesting in each country is shown in the last column.
46
Table 11. Estimates per country of road surface, potential cultivation area (in cultivated lands), potential
runoff volumes and number of households that could benefit from road runoff
Road surface in
Road surface in
Cultivation area Total runoff volumes
Households
rangelands
cultivated lands
(in cultivated
lands)
Assumptions: 5 m width
Country
Angola
Benin
Botswana
Burkina Faso
Burundi
Cameroon
Cape Verde
Central African Rep
Chad
Comoros*
Congo
Congo Dem Rep
Cote d’Ivoire
Djibouti
Equatorial Guinea
Eritrea
Ethiopia
Gabon
Gambia The
Ghana
Guinea
Guinea-Bissau
Kenya
Lesotho
Liberia
Madagascar
Malawi
Mali
Mauritania
Mauritius
Mozambique
Namibia
Niger
Nigeria
Rwanda
Sao Tome & Principe
Senegal
Sierra Leone
Somalia
South Africa
Sudan
Swaziland
Tanzania
Togo
Uganda
Zambia
Zimbabwe
TOTALS
ha
3,344
356
5,209
18,274
95
1,306
264
75
6,936
0
0
684
0
613
0
800
3,259
0
756
3,125
51
0
4,576
876
0
1,158
1,866
4,346
1,707
0
3,360
8,182
3,757
14,876
206
0
2,707
0
4,166
57,276
2,001
488
10,892
736
1,544
7,048
18,875
195,789
10 m
width
5 m width
10 m
width
C/CA = 2:1
Low
estimates
High
estimates
1 each 500 m
of road
ha
ha
ha
ha
m3
m3
(number)
30,265
3,219
47,149
165,398
857
11,819
2,391
681
62,780
0
0
6,192
0
5,546
0
7,243
29,500
0
6,839
28,283
464
0
41,417
7,925
0
10,479
16,889
39,332
15,450
0
30,409
74,050
34,008
134,640
1,867
0
24,499
0
37,705
518,398
18,107
4,415
98,579
6,661
13,977
63,788
170,835
1,772,056
6,688
711
10,419
36,549
189
2,612
528
151
13,873
0
0
1,368
0
1,225
0
1,601
6,519
0
1,511
6,250
102
0
9,152
1,751
0
2,316
3,732
8,691
3,414
0
6,720
16,363
7,515
29,752
413
0
5,414
0
8,332
114,552
4,001
976
21,783
1,472
3,089
14,095
37,750
391,578
1,700
181
2,649
9,292
48
664
134
38
3,527
0
0
348
0
312
0
407
1,657
0
384
1,589
26
0
2,327
445
0
589
949
2,210
868
0
1,708
4,160
1,911
7,564
105
0
1,376
0
2,118
29,123
1,017
248
5,538
374
785
3,584
9,597
99,554
3,401
362
5,298
18,584
96
1,328
269
77
7,054
0
0
696
0
623
0
814
3,315
0
768
3,178
52
0
4,654
890
0
1,177
1,898
4,419
1,736
0
3,417
8,320
3,821
15,128
210
0
2,753
0
4,237
58,247
2,034
496
11,076
748
1,570
7,167
19,195
199,107
1,275
136
1,987
6,969
36
498
101
29
2,645
0
0
261
0
234
0
305
1,243
0
288
1,192
20
0
1,745
334
0
442
712
1,657
651
0
1,281
3,120
1,433
5,673
79
0
1,032
0
1,589
21,843
763
186
4,154
281
589
2,688
7,198
74,665
1,513,269
160,935
2,357,444
8,269,880
42,872
590,950
119,529
34,057
3,139,005
0
0
309,617
0
277,282
0
362,159
1,475,023
0
341,947
1,414,145
23,176
0
2,070,835
396,251
0
523,959
844,469
1,966,615
772,498
0
1,520,474
3,702,525
1,700,413
6,732,000
93,356
0
1,224,940
0
1,885,252
25,919,897
905,351
220,737
4,928,931
333,034
698,865
3,189,379
8,541,745
88,602,816
3,026,539
321,870
4,714,888
16,539,760
85,744
1,181,900
239,058
68,114
6,278,009
0
0
619,234
0
554,563
0
724,318
2,950,047
0
683,894
2,828,291
46,353
0
4,141,670
792,502
0
1,047,918
1,688,937
3,933,230
1,544,995
0
3,040,947
7,405,049
3,400,827
13,464,001
186,712
0
2,449,879
0
3,770,505
51,839,794
1,810,701
441,474
9,857,861
666,068
1,397,730
6,378,758
17,083,491
177,205,632
This table presents estimates of the road surface per country that would be available for road runoff harvesting divided
amongst rangelands in cultivated lands. Also listed are estimates of total runoff volumes for rangelands and cultivated lands
combined. The cultivation area was calculated based on the average road surface in the cultivated lands. The last column
shows the number of households that could benefit from road runoff harvesting, in both rangelands and cultivated lands,
assuming that on average a stretch of 500 m road is used per household.
47
5. Analysis
5.1 Technical performance
All six sites are located in arid, semi-arid or dry sub-humid areas at an altitude between 1100 – 1300 m
above sea level. The land is hilly with slopes of 2 to 5%. Soils have limited fertility and are sandy to
loamy, allowing for good infiltration of rainwater as well as drainage. Problems that are encountered are
related to the loss of fertile soil due to water and wind erosion. Agroforestry is common practice,
especially by those farmers who have started implementing soil and water conservation techniques.
Many farms in both Mwingi and Machakos Districts have adopted fanya juu and or fanya chini terraces,
though with varying degrees of efficiency. The farmers that were visited, however, have correctly
introduced the terraces, following the contours lines and choosing the right distance between the
channels (depending on the slope of their land). Only David Kyula (site #5) has not created an elaborate
terrace system.
Road runoff harvesting is practiced by each farmer in a different way. Three phases in the treatment of
runoff can be distinguished: collection, intermediate storage and distribution (see Table 12). Besides
Muindu Musyoka (site #1), all farmers first collect the water in a pond. The latter have the advantage that
they can use the pond water to bridge dry spells during the growing season, while Musyoka’s system
simply increases the water in the soil immediately after a shower, thus without being able to control the
timing of irrigation.
Table 12. Overview of rainwater harvesting elements on the six farms
Site Farmer
Collection
Storage
Distribution
Crops
Flooding of fanya
#1
Mr. Muindu
Culvert
No storage
Maize, beans,
chini and fanya juu
Musyoka
Drains
banana, sugar
terraces
cane, cassava
#2
Mr. Mwema
Drains
Pond (unlined, downhill)
Supplementary
Mango, lemon,
Maswili
irrigation with jerry
pawpaw, guava
can
#3
Mr. Samuel
Drains
Pond (lined, with silt trap,
Rope-and-washer
Fruit trees, beans,
Mweu Maingi
downhill)
pump and hose
peas, vegetables
#4
Unknown (a
Drains
Pond (lined)
Tread pump, ‘water
Tomatoes
neighbour of Mr
tower’, greenhouse
Samuel Maingi)
with low-head drip
irrigation
#5
Mr. David Kyula Drains
Pond (unlined, with large
Buckets and hose
Maize, vegetables
Small culvert earthen and small silt
(+seepage to
trap, uphill)
neighbouring field)
#6
Mr. Sammy
Drains
Underground tank and
Hose (?)
Mango, orange
two aboveground tanks
(plastic, 2,5 m above
ground, with diesel pump)
This table summarises which rainwater harvesting elements are used on each site (collection, storage and
distribution of runoff) and lists the main crops that are grown in each system.
Lined ponds have the clear benefit of not losing water through seepage. Evaporation takes places in all
ponds however, as none of them are covered. The other farmers use simple techniques to irrigate their
crops and trees with the water from the pond: varying from a bucket or jerry can to a treadle or rope-andwasher pump. The most advanced irrigation system is used on the farm of Samuel Maingi’s neighbour
(site #5) and his colleague farmers: they have invested in a greenhouse with drip irrigation system. This
system allows for the production of high value cash crop like tomatoes, capsicum and onions.
48
Tools that are used for (manual) construction and maintenance of the structures are generally simple and
include hoe, shovel, panga and wheel barrow.
The technical performance of each site is shortly described in Table 13. For the first two case studies the
actual C/CA ratios have also been estimated. Muindu Musyoka’s farm and Mwela Maswili’s farm have
rather small ratios (1.1/1 and 1.7/1, respectively), considering an expected ratio of 2/1 to 10/1 for external
catchments (Critchley and Siegert, 1991). The calculated sizes of the two areas of Musyoka’s farm (6.5
ha/6.0 ha) are also different from the original estimates by Mutunga and Critchley (2001; 10 ha/5 ha). The
rough estimates of the optimal ratios (6.5/1 and 2.4/1, respectively.) indeed fit better with average ratios
for rainwater harvesting with external catchments. Nevertheless, the calculated ratios are rough estimates
and would require detailed sampling and analysis for establishing more accurate actual and optimal
ratios.
Table 13. Description of the technical performance of each site
Site
#1
Technical performance of measures for runoff collection, storage and use
Musyoka’s flooding approach works well but is entirely based on water conservation in the soil.
Supplementary irrigation during dry spells in the rainy season is not possible with this system.
Harvesting of runoff from across the road is also not optimal because of the water lost due to
infiltration in the catchment area (resulting in a lower runoff coefficient).
#2
Maswili has constructed a pond that gives him enough water in times of rain. The pond, however,
works far from optimal, because a lot of water is lost through cracks in the floor and wall.
Evaporation also affects the availability of stored water. Water enters the pond unfiltered. Owing to
the fact that the pond is located downhill, irrigation is done by moving the water uphill with a jerry
can.
#3
Maingi has a pond lined with polythene which has proven to be a durable material. The pond has a
‘one-way’ silt trap where water can only enter the pond. An outlet at the side prevents water from
overflowing the pond, but also makes that dirty water enters the pond through the silt trap.
Evaporation is the only factor contributing to water loss from the pond. The pond is located downhill
which means the farmer has to use a (leaking) rope-and-washer pump to transport the water four
terraces higher. Nevertheless, the road runoff harvesting represents an (important) improvement
for this farmer.
#4
Maingi’s neighbour has a lined pond more or less at the same level as the greenhouse.
Evaporation is a cause of water loss from the pond. Water distribution is efficient due to the drip
irrigation system in combination with the greenhouse-tent that reduces evapotranspiration from the
tomato plants.
#5
Kyula uses an innovative silt-trap made of earth in combination with a smaller silt-trap. It is not
clear where the outlet is in case of overflow. The large pond could be improved by lining and
covering it. However, the advantage of water seeping into the ground is that the neighbouring
cultivation area – which belongs to the farmer himself and to his neighbour – directly receives
water, allowing for a thriving vegetable garden and fruit trees, respectively. The distribution system
is functional yet very simple with a bucket-hose construction. The advantage is that the pond is
located uphill in relation to the cultivation area.
#6
Sammy has a sophisticated storage system that is composed of two elevated tanks and a diesel
pump. It is not clear whether this height advantage is also used for irrigation purposes.
The use of roadside drains and culverts requires limited knowledge, at least at first. With trial-and-error,
both Muindu Musyoka and Mwela Maswili have started tapping road runoff. The set up of Musyoka’s farm
has changed very little since 2000.
The creation of a pond requires some basic knowledge. The volume and size of the pond should be
optimal for the amount of runoff that is collected.
49
The technical knowledge required for the greenhouse is relatively complicated and requires support from
external agents. To provide the necessary knowledge, trainings were organized and technical support
offered during the first year. If not properly dealt with, the greenhouse could become useless.
The additional measures like fanya juu and fanya chini terraces can best be implemented by seeking
advice from extension officers, peace workers or researchers that are active in the region.
In summary, the technical performance of all sites is in general sufficient but could be improved with small
adaptations (e.g. lining of pond, or a better pump) as well as more with more sophisticated measures
such as drip irrigation kits. The required knowledge is minimal for runoff collection, while runoff storage
and efficient distribution tools may require more advanced knowledge to ensure proper instalment and
use.
5.2 Economic viability
Smallholder farmers living Mwingi and Machakos District are relatively poor. Off-farm income plays a role
and varies in kind. Production is first for subsistence and in a second place for selling cash crops. Water
supply is limited and agriculture is predominantly rainfed. Only one groundwater irrigation system was
observed near Mwingi town (this site was not included in this study); the well was created by peace
workers next to a sand river. The size of the cropland is generally limited to a few hectares. Land is
cultivated using manual labour and animal traction. Agricultural services are limited and depend on the
availability and pro-active approach of extension workers and development agents. Small towns and
cities have markets were agricultural goods are sold.
The costs for establishing and maintaining a road runoff harvesting system depend on how elaborate the
system is. The creation of roadside drains is done by farmers themselves and only requires a time
investment. Establishing a pond already requires a larger investment – which becomes higher if proper
lining is put in place. Adding more sophisticated irrigation tools further increases the size of the
investment. Additional measures like fanya juu and fanya chini terraces represent a relatively low cost.
Table 14. Benefit-costs analysis of the road runoff harvesting systems of Musyoka and Maswili
Cost item
RRH system of
Muindu Musyoka
Construction terraces
Construction pond
Total investment costs
471
N.A.
471
173
1260
1433
5
26
19
5
200
195
52 seasons
(26 years!) (assuming
US$ 10 of net benefit
can be used per season)
8 seasons
(4 years)
(assuming US$ 185 of
net benefit can be used
per season)
Overall maintenance
Average return seasonal return
Net benefit on investment per season
Payback time
RRH system of
Mwema Maswili
50
A ‘back-of-the-envelope’ benefit-cost analysis was carried out for the two case studies (see Table 14.).
For Musyoka, average seasonal maintenance costs were roughly estimated to be US$ 5 (based on the
most recent repair in 2009 (see Table 8. Average seasonal return was calculated based on the fact that
yields have varied greatly since the establishment of the road runoff harvesting system, and by assuming
that the 2007 yields were ‘high’ yields – the average seasonal return was thus estimated at only US$ 26
(which is half of the average of both 2007 seasons). For Maswili, the seasonal maintenance costs were
also estimated at US$ 5. Economic benefits however were estimated at US$ 200, considering the recent
income generated with the sales of maize, mango and water. To calculate the pay-back time in the
absence of information regarding the benefits and costs of their farming system prior to the introduction of
road runoff harvesting, it was assumed that part of the net seasonal benefit (US$ 10) is spent on activities
that would take place also without the using road runoff. The pay-back time for Musyoka thus becomes a
remarkably long period of 52 seasons, while the pay-back time for Maswili is approximately 8 seasons.
Interestingly, Musyoka evaluated the overall benefits both on the short and long-term as ‘positive’. Maswili
said he is ‘very positive’ about the short and long-term benefits.
The third and fourth site (of Maingi and his neighbour) showed promising results: the pay-back time for
Maingi’s pond was estimated at 6 seasons, while he said the system of his neighbour (with the
greenhouse and drip-irrigation system) only required 3 seasons to pay back the initial investment of
somewhere between US$ 1,700 – 2,700. Lastly, David Kyula and Mr Sammy also seemed very positive
about the returns generated with their water reservoirs, despite the relatively high investment costs.
The marketing infrastructure is in place for traditional crops (maize, beans) and ‘new’ crops (e.g. mango,
tomato). Tomatoes, for instance, are economically competitive in Masii town. Maingi (site #3) notes that
some farmers also practice aquaculture in their ponds – without as much commercial success, however,
because fish does not sell well on local markets as it is not an element of traditional diets.
Extra income can also be generated without crop production as the case of Maswili demonstrates: the
extra time and money he has available allows him to produce and sell honey.
The overall evaluation of costs and benefits by the farmers was deemed positive to very positive. For the
two case studies, the economic effects are positive both in the short and long term (i.e. beyond 10 years).
The farms of Maingi and his neighbour (sites #3 and 4) have a pay-back time of six and three seasons (or
3 and 1.5 years), respectively.
Thus, despite a wide variation in the use of collection, storage and application techniques as well as
largely differing initial investments, all visited sites seem to be economically viable. Farmers do not keep
track of the exact benefits and costs. Road runoff harvesting has enabled farmers to diversify crop
production and successfully develop new sources of income.
5.3 Environmental friendliness
The major benefit of collecting runoff from road on the environment is, looking at the six visited sites,
probably the increase in agricultural production due to improved soil and water conservation. The richer
crop and fodder diversity is likely to have a positive impact on the diversity of organisms in the soil, and
therefore also on the carbon and biomass stored under- and aboveground. A benefit of Musyoka’s farm
may also be that (severe) soil erosion and gully formation at the outlet of the culvert is foregone, thus
sparing the land of his sister.
The availability of flowering plants and (downstream) water in the vegetable garden of Kyula attracts
insects like butterflies and bees and thus contributes to the local biodiversity. The fact that Maswili (site
#2) has been able to start keeping bees also contributes to the diversity of animals and plants (that are
pollinated by the bees).
51
Table 15. Environmental impacts and related Ecosystems Services of the studied road runoff harvesting
sites
Environmental impact
Ecosystem Service (ES)
ES type
Increased plant growth and
diversity
Biological production, carbon storage,
more biodiversity
Provisioning;
Regulating
Increased soil biodiversity
Improved nutrient cycles, more
biodiversity
Supporting;
Regulating
Increased insect diversity (bees
and other insects)
More pollination, more biodiversity
Regulating
Increased soil moisture and
streamflows
Water availability
Regulating;
Provisioning
Increased amount of soil nutrients
and reduced soil erosion
Nutrient availability
Supporting
Table 15 shows the observed environmental impacts in relation to ecosystem services in the drylands.
Negative impacts on the environment have not been observed. However, aquaculture that is practiced in
ponds on other farms in Machakos may have negative environmental impacts due to use of fish feed
(ecological footprint) and possibly of hormones.
5.4 Social acceptance
The social circumstances are more or less similar for the two case studies and the four additional sites.
The technology is applied in an agricultural area with between 10-50 people per square kilometre. Land
and water rights seem to belong to the farmers (it has not been able to confirm this at the last four sites).
Land is usually cultivated with manual labour and sometimes with help of animal traction.
The first two road runoff harvesting sites, which have been developed independently Musyoka and
Maswili, represent two cases of local innovation. Additional measures (terraces, pond) were added later
with help of external agents. For the other sites it is not clear where the idea of using runoff from drains
originated, yet is not unlikely that this has also been done through trial and error by the farmers
themselves. Further improvements and extensions of the systems (with lined ponds, silt traps, pumps,
irrigation system and greenhouse) have been done with the support of extension workers.
Social impacts can be divided into on-farm and off-farm impacts. On-farm, families of the farmer benefit
from the increased food production. Disadvantages for people living on the farm have not been recorded.
Gender issues were not observed – though all farmers who applied road runoff harvesting were men.
Off-farm, the six sites show that both positive and negative consequences can be associated with road
runoff harvesting. The negative impacts include:
•
•
Upstream neighbours may be affected because water is guided through their field
The wave of attention that Musyoka (site #1) has received over the past decade, has also led to
negative reactions by farmers in the area, who would like to be treated equally
52
The positive impacts include:
•
•
•
•
•
•
Neighbours benefit from the collected water that may be sold by a farmer
Farmers in the area can benefit from the knowledge of a farmer, especially if the farmer
organises on-site trainings
Other farmers may also benefit from the increased pollination (due to the increased bee
population) and availability of honey
The creation of additional measures (terraces, ponds) generates temporary labour opportunities
The increased production may also create more sustainable jobs, e.g. for planting and irrigation
activities
Greenhouses require a pooled investment of several farmers, which may lead to more social
cohesion and knowledge exchange, and allow for larger projects
Figures related to adoption of similar road runoff harvesting technologies by other farmers are scarce
(see
Table 16). Musyoka (#1) says he knows of 8 farmers who have started collecting road runoff. Maswili (#2)
on the other hand is not aware of any other farmer who has taken over his approach – his neighbour (who
gave him the idea of using fanya juu terraces) is “too lazy” to tap road runoff. The greenhouse kit has
been purchased by 20 other (groups of) farmer(s) in the area of Machakos where site Maingi’s farm is
located (#4).
Table 16. Adoption rates and reasons for successful or unsuccessful adoption
Site
District
Adoption
Reason
#1
Mwingi
8 farmers*
Extension work
On-farm training by Muindu Musyoka
#2
Machakos
0 farmers
Lack of interest
#4
Machakos
20 community projects with
Marketing of greenhouses by World
greenhouses
Vision and their partners
Training by World Agroforestry Centre
(ICRAF)
Active involvement local administration
* According to Mutunga and Critchley (2001), even around 40 farmers have adopted road runoff harvesting following the example of
Muindu Musyoka.
No information was available on adoption rates on the other three sites.
5.5 Factors that may influence the adoption of road runoff harvesting
The decision of a farmer to adopt a new technology like road runoff harvesting depends on a wide range
of factors – moreover, poor smallholder farmers in semi-arid environments tend to be risk averse due to
the many uncertainties they face (Ngigi et al., 2005a). Many authors (see e.g. Critchley, 2009) emphasize
the need for taking into account the local socio-economic and cultural conditions that determine whether
farmers will adopt a technology or not. This study did not focus specifically on the adoption factors of
farmers; nevertheless, some potential factors influencing the adoption can be retrieved from the input
farmers at the different sites provided (see Table 17). The table, in a way, represents an extended
benefit-cost analysis incorporating technical, economic and social factors. The factors are given a positive
or a negative balance according to examples in this study.
53
Table 17. Overview of potential adoption factors derived from data gathered at the six farms
Description of adoption factor
+
Technical factors
-
Simple collection techniques (drains /
diversion channels)
Simple storage techniques (e.g.
unlined/lined pond)
Simple runoff application techniques
Economic factors
Social factors
Good technical guidance from external
agents
N.A.
More or less equal agricultural input
required
Increased production – increased
income
Quick pay-back time
Creation of new sources of income (e.g.
beekeeping)
N.A.
General interest in new technologies;
Idea (in part) based on personal / local
knowledge;
Creation of employment
Need for cooperation with other farmers
General interest in change / innovation
(leader)
N.A.
Clearly established land and water
rights
Risk of erosion
More sophisticated storage facility
-> Lack of adequate knowledge and tools
Possibility of failing structures
More sophisticated runoff application
techniques
-> Lack of adequate knowledge and tools
N.A.
High establishment and maintenance costs
(labour, materials)
N.A.
N.A.
Slow pay-back time
N.A.
Need for credit (family, bank or otherwise)
Scepticism towards new technologies
N.A.
Need for cooperation with other farmers
General disinterest in change / innovation
(lagger)
Risk of conflict with upstream or
downstream neighbour
N.A.
Ngigi et al. (2005a) report that, amongst the technical factors that influence the adoption of water
reservoirs, farmers may refrain from constructing water reservoirs because of the perceived risks of water
loss due to seepage and evaporation. The farm pond of Samuel Mweu Maingi shows that, if proper
support from extension services is available, ponds are adequately lined with durable materials.
Establishment and maintenance of sophisticated drip-irrigation / greenhouse systems require specialist
knowledge (Ngigi, 2008). Such knowledge can be provided if development agents – such as World Vision
International, ICRAF and Amiran Ltd. – cooperate effectively.
High investment costs for labour and/or material are often major constraints for the uptake of rainwater
harvesting technologies (Ngigi, 2003a). As the case studies suggest, the channels and drains for the
collection and diversion of runoff can be built by the farmer for free, provided he has time to do this. A
similar situation can be observed with the banana plantation of in Uganda (Ibid.). The major costs are
associated with the (optional) storage and distribution technologies. Also, complementary soil and water
conservation measures (e.g. terracing) may also be costly. Absence of credit facilities is another potential
economic barrier for adoption (Critchley, 2009).
Openness to innovation is also a factor influencing the uptake of new technologies like road runoff
harvesting. Muindu Musyoka and Mwela Maswili both started diverting road runoff through trial and error.
Only later they learned about soil and water conservation measures like fanya juu and fanya chini
terraces, which they ‘added’ to their water harvesting system years later. In contrast, Ngigi (2003) argues
that farmers using in-situ soil and water conservation measures are more likely to adopt a storage
rainwater harvesting system. Both ways seem thus to be possible for farmers to adopt (road) runoff
54
harvesting. Following Critchley (2007), Musyoka and Maswili can be considered farmer innovators. For
their innovations, they use ´hybrid´ knowledge, i.e. local ideas supported by scientifically proven
techniques. Their willingness to adopt is high compared to other farmers in the area (e.g. Maswili´s
neighbour) – they are early adopters.
With respect to the other farmers it is not clear who initiated the innovation process. The installation of
greenhouses with drip-irrigation kit is actively being promoted by Amiran Ltg and/or World Vision
International in Machakos region, which probably explains the fact that the groups of farmers (including
Maingi’s neighbour) have become acquainted with this technology.
5.6 Sensitivity analysis of the sub-Saharan Africa-wide assessment
The first main outcome of the assessment is that around 0.5 cubic kilometre of runoff could be collected
from roads and road sides. The second main result is that roughly estimated, a total of 2.2 million
households (or 11.7 million people) could benefit from road runoff harvesting. These two figures are
based on a number of assumptions. Table 18 gives an overview of the 13 assumptions and the impact
changes in these assumptions could have on 1) the potential gross runoff volume and 2) the total
estimated number of households that can potentially make use of road runoff harvesting.
This sensitivity analysis demonstrates that the estimated potential runoff volume generated through road
runoff harvesting through road runoff harvesting can drastically change if assumptions are not taken into
account or if upper or lower ranges of the assumptions are taken. In the most pessimistic scenario, less
than 0.026 cubic kilometre of gross runoff could be available, while under the most favourable conditions
1.5 cubic kilometre or more could be use for road runoff harvesting.
The estimated number of households that could be supported by road runoff harvesting measures is
similarly sensitive to changes in the assumptions. In the least favourable situation, less than 114,000 (or
less than 5.2% of 2.2. million) households can potentially benefit from road runoff harvesting. In contrast,
in the most optimistic scenario harvesting road runoff could help over 5.9 million (269% of 2.2 million)
households.
55
Table 18. Sensitivity of the outcomes (potential runoff volume and number of households) of the subSaharan Africa-wide assessment
Assumption
Change to the assumption
Impact on 1) estimated
potential runoff volume
and 2) total number of
households that could
benefit from road runoff
harvesting
1.
Total length of rural roads is sum of
classified (World Bank figures) and
unclassified rural roads, and length of
unclassified roads can be estimated by
multiplying the length of classified roads by
1.74 (i.e. total rural roads is 2.74 times
World Bank figures)
Countries do not have roads
other than those reported by
the World Bank
Reduction with 64%
2.
Road density is (fully) correlated with
population density
Road density is equal across
the whole country
Increase with 11%
3.
Cultivated lands and rangelands make up
30 and 59% of drylands (respectively) and
this amount of land cover is spread equally
over all countries and regions
Cultivated lands and
rangelands make up less or
more of drylands
Increase with max. 11% or
reduction that could be
larger in theory
4.
Cultivated lands are only rainfed (no land
is irrigated)
Cultivated lands are rainfed
for 95% (NB. rangelands are
not included)
Decrease with max. 1.7%
5.
Between 0.25 and 2 culverts can be found
on a random stretch of 1 kilometre of road
(average 1.12 per kilometre)
Average 0.25 or average 2
culverts per kilometre
Decrease or increase with
78%
6.
Roads (plus roadsides) have an average
width of 7.5 metre
Average 5 or average 10 m
Decrease or increase with
33%
7.
25% of both culverts and road(side)
surfaces are suitable for road road runoff
harvesting
Less or more
Decrease or increase
8.
Average annual rainfall depth is 300 mm
across the drylands
Average annual rainfall
depth is lower or higher
across the drylands
No impact on number of
households (in this
assessment)
Decrease or increase of
runoff volume
Runoff coefficient (K) is 0.2 and efficiency
factor (E) is 0.5
10. Average catchment size for culverts is 1
hectare
Runoff coefficient is higher,
in particular on paved roads
Average catchment size is
smaller or larger
Increase
11. 1 household can benefit from 1 (suitable)
culvert
More than 1 household can
benefit from 1 culvert
12. 1 household can benefit from a stretch of
500 m of road (with an estimated average
width of 7.5 metre)
More than 1 household can
benefit from a stretch of 500
m (for instance when only a
few infiltration pits are used
by each farmer)
Increase
13. 1 household consists on average of 5.3
persons
Less persons per household
benefit from the road runoff
harvesting (e.g. Tiffen et al.
(1992) reported an average
of approximately 4 persons
per household;
No impact on the number of
households (decrease of
some 20% or more in
number of people)
9.
56
No impact on household (in
this assessment)
Decrease or increase of
runoff volume
Increase
6. Discussion
6.1 Addressing the research questions
The research carried out for this thesis focused on the question what the potential is for practicing and upscaling road runoff harvesting in sub-Saharan Africa. More specifically, the aim of this thesis is to give an
answer to the following two sub-questions:
1) What is the performance of existing road runoff harvesting systems in terms of sustainability?
2) What is the (bio)physical potential for up-scaling the use of road runoff harvesting in the drylands
of sub-Saharan Africa?
The following two sections address these questions in the same order. Subsequently, the experience of
using the WOCAT Questionnaire for SLM Technologies in combination with the TEES-test is described in
the subsequent section. The last section presents the elements of the sub-Saharan African-wide
assessment that require further refinement.
6.2 Performance of road runoff harvesting sites
The outcomes of the TEES-test suggest that road runoff harvesting – with roadside drain(s) or from
culvert(s) – is a welcome addition to the existing yield-increasing measures that smallholder farmers can
benefit from to better cope with the unreliable and erratic rainfall in the arid and semi-arid regions of subSaharan Africa. While the two case studies were chosen to evaluate road runoff harvesting through
culverts and with roadside drains, the other four sites only shed more light on the different ways roadside
drains can be used to harvest runoff. It should be re-emphasized that this study has focused only on
farms were road runoff harvesting has (successfully) been adopted. Examples of failures have not been
identified either prior or during the fieldwork. The results are in line with the promising prospects of other
case studies that were found in literature.
Table 19. Structural adjustments that could make road runoff harvesting structures more efficient.
Structural measure
Improve / introduce terraces
Adapt cultivation area to the catchment
area (i.e. improving the C/CA ratio)
Add / improve silt traps at the pond inlet
(e.g. with Y or T inlet)
Create an (uphill) pond
Line pond / improve lining
Cover pond
Use better hand/foot pump (e.g. ropeand-washer pump or treadle pump)
Introduce low-head drip irrigation
Use a greenhouse
Benefit
Improved water distribution and
conservation
Improved water use efficiency
Investment required
Low
Less siltation of pond; creation of
fertile “green soup”
Water available for supplemental
irrigation
Prevention of seepage
Prevention of evaporation
Efficient water use
Low
Efficient water use
Efficient water use
Medium - High
High
Low
Medium – High
Medium
Medium
Low
This is not to say that the road runoff harvesting systems in this study perform perfectly well. Many are
the small or large technical modifications that could be made to make existing systems more efficient and
effective. For instance, Mutunga and Critchley (2001) point out that making the channels on Musyoka’s
57
farm shallower would allow more runoff to spill over onto his land (in fact, this suggestion was made by
farmers who visited his farm and evaluated his land management measures). Table 19 lists some of the
changes that could be made to the structures. Besides structural modifications, other measures
(agronomic, vegetative and management-related) could also be taken to enhance the efficiency of the
systems (see e.g. WOCAT, 2007).
From an economic investment perspective, the returns from selling more – and more diverse –
agricultural produce seem to justify the farmers’ decision to adopt the road runoff harvesting system. Payback times seem to differ greatly, depending on the type of runoff collection, storage and distribution. For
well-managed greenhouses, pay-back times of 1 season may even be possible (Ngigi, 2009, referring to
a document of the Organic Farmer). Besides the example of Ngigi (2003a: 218), no other studies on the
economic viability of road runoff harvesting were found to complement these results. Few detailed
economic assessments of rainwater harvesting technologies in general – either at the farm level (e.g.
Barron, 2004; Fox et al., 2005; Ngigi et al., 2005; Hatibu and Mahoo, 2000) or at an aggregate
(watershed or community) level – have been carried out up to date (Critchley, 2009). The general
feedback regarding road runoff harvesting is that labour represents the major investment cost for
resource-poor farmers (Ngigi, 2003a; Critchley et al., 1999; ICRAF, 2012). This is supported by the two
case studies. However, more sophisticated road runoff harvesting systems which incorporate lined ponds,
drip irrigation kits and greenhouses, involve relatively high equipment costs. A comprehensive benefitcost analysis of the case studies and other sites is needed to confirm these preliminary findings.
Analysis of the environmental impacts shows that road runoff harvesting may contribute to several
ecosystem services that are characteristic for Africa’s drylands (Safriel et al., 2002; see Box 1). Negative
impacts on the environment, biodiversity and ecosystem services’ functioning were not recorded for the
six sites. The lack of direct downstream neighbours may explain why, on the farms of Muindu Musyoka
and Mwema Maswili, changes in downhill water provision have not been perceived. Nevertheless,
downstream impacts on the surface (and sub-surface) flows need to be seriously considered as the case
studies described by Ngigi (2003a) demonstrate.
From a social point of view, the upstream-downstream impacts on the six sites are limited to a minor
conflict on the farm of Muindu Musyoka. As other studies have shown, however, there is a clear potential
for conflict between farmers and even between communities when road runoff harvesting is practiced on
wider scale (Ngigi, 2003a).
6.3 Potential for up-scaling road runoff harvesting in sub-Saharan Africa
Road runoff harvesting can only be practiced by those farmers and pastoralists whose land is located in
the proximity of a road. This sets a limit to the potential for up-scaling road runoff harvesting. Road runoff
harvesting should be seen as an additional (water harvesting) technology that could benefit a selected
group of smallholder farmers and pastoralists. (A large variety of rainwater harvesting technologies exists
that smallholder farmers can use to upgrade their rainfed farming systems. These are all adapted to the
prevailing local conditions and can thus each support a selected number of farmers or pastoralists.) The
preliminary estimates presented in this study exclude the opportunities and barriers that exist at the
social, economic and environmental level and thus do not include, for instance, the potential downstream
impacts that up-scaling could trigger.
Considering the physical suitability of roads, the results of the sub-Saharan Africa-wide assessment
suggest that 2.2 million households or 11.7 million people could benefit from road runoff harvesting. This
figure represents 3.6% of the total population living in the drylands (Murray et al., 1999). This percentage
is higher if only the people who directly depend on agriculture or pastoralism, are taken into account. Due
to the considerable number of assumptions that were necessary for this assessment, it is important to
58
realise that these outcomes present only a rough estimate of the potential for up-scaling road runoff
harvesting. Indeed, the sensitivity analysis shows that these figures merely represent an indication of the
potential for upgrading the collection and use of road runoff. The potential runoff from roads in subSaharan Africa, around 0.5 cubic kilometre, represents approximately 0.01 % of the gross volume of
annual runoff that is generated in Africa as a whole – some 5,195 cubic kilometres (Malesu et al., 2006).
However, it is not known what percentage of this total runoff in Africa is used for agriculture. It was not
possible to quantify the potential impact of up-scaling road runoff harvesting on rainfed agriculture in subSaharan Africa.
As the sensitivity analysis in the previous chapter shows, the outcomes must be regarded with care. A
first, important consideration is that the estimated road lengths in the rangelands and cultivated lands
may significantly differ from the current estimates. First, this is because the total road length is based on
the assumption that ‘unclassified’ rural roads have not been taken into account. Though this may be true
for Kenya, this remains to be verified for all other countries. If this assumption is proven wrong, a more
than 60% lower estimate of the road network length would be the result. Second, the share of rangelands
and cultivated lands is based on world averages. These shares will most likely differ from country to
country. Third, the road lengths have been estimated assuming that road density is fully correlated with
population density. A more accurate estimate of road densities in the drylands could positively or
negatively affect the present results.
Another consideration is that the expected runoff volumes are based on several assumptions. An annual
rainfall of 300 mm was taken to estimated runoff volumes in the drylands as a whole. As this is the upper
limit of rainfall in the arid zones, higher rainfall depths can be expected for the semi-arid and dry subhumid zones. In turn, higher runoff volumes could benefit more land and/or more people. Also, the size of
the catchment area of culverts was roughly set at 1 hectare. Depending on the layout of the river basin
and the position of the road, the catchment area of a culvert may be smaller or larger than 1 hectare. This
is also reflected by the size and number of culverts on a given stretch of road. Similarly, the catchment
area represented by the surface of road and roadsides may be very different and depends on the slope,
width and length of the suitable parts of both road and roadside. These factors will in the end determine
what the total amount of runoff is that can be collected from road surfaces and culverts.
Lastly, the estimates of the number of households that could benefit are based on the assumption that
one culvert or an average stretch of 500 metre road can benefit one household (or 5.3 people).
Considering the potentially large difference in catchment area size and hence runoff volumes, the
potential number of households may largely differ from the estimated 2.2 million. In principle, road runoff
harvesting can be practiced using, for instance, only a few banana planting pits. Also, a large culvert may
provide enough runoff for several farmers at a time.
6.4 Experience of using WOCAT and the TEES-test
The WOCAT Questionnaire for SLM Technologies is very long and detailed, which requires a lot of time
and effort from both interviewer and interviewee. This is also pointed out by Schwilch et al. (2011). Filling
in the questionnaire requires experience in asking the right questions, especially when the questions and
answers have to be translated. Furthermore, analysis of benefits and costs is not straightforward (Ibid.).
Incorporating the elements of the WOCAT Questionnaire for SLM Technologies into the four categories of
the TEES-test (plus a ‘general’ category) and a limited number of sub-categories seems to have the
following advantages:
59
1) Comparison of data between different questionnaires is facilitated due to the limited number of
categories; this includes comparison with data from a revisited site (i.e. monitoring and
evaluation) – it is easier to point out the differences
2) More emphasis is given to the social and environmental impacts, which often receive less
attention than technical and economic aspects. These aspects are important to take into account
when the sustainability of a technology is assessed. In addition, these aspects are also directly
related to the potential for (wide-scale) adoption.
3) It is more obvious when new elements have been added (such as the C/CA ratio)
4) Conditions (general context) are clustered and separate from characteristics (measures,
knowledge required, benefits, disadvantages etc) of the Technology
5) Analysis of benefits and costs and/or disadvantages is more straightforward, also because
nd
rd
quantitative and qualitative data from the 2 and 3 section of the questionnaire are combined.
6) Presentation / communication of the questionnaire data is facilitated, i.e. it is not necessary to
refer to four-digit questions
7) Comparison/combination with other tools is less complicated, for instance with a Social CostBenefit Analysis, an Environmental Impact Assessment, (Valuation of) Ecosystem Services,
sustainability criteria of ESTs
This is the first study that combines WOCAT with the TEES-test. The TEES-test itself is not a fully
developed tool and needs further refinement to turn it into a (strong) scientific tool. Linking it with WOCAT
seems to be a good start to find answers to the questions related to the technical, economic,
environmental and social performance.
6.5 Refining the sub-Saharan Africa-wide suitability assessment
The present assessment gives a first, preliminary indication of the physical potential for up-scaling road
runoff harvesting in sub-Saharan Africa. This potential varies from country to country. For a more
comprehensive assessment, the following information needs to be taken into consideration for each
country:
-
-
The length of classified and unclassified rural roads
The road density per dryland area
The share of rangelands and cultivated lands per dryland area
The topography of the area (exclude slopes where road runoff harvesting cannot be
practiced)
The number of culverts (from national or regional road administrations)
Data from ground truthing (to adjust estimates regarding e.g. average road width, number of
suitable culverts, size of culverts, share of suitable road surface, size of catchment for both
culverts and road surface, presence and size of gullies, size of cultivation areas, size of pans
or other reservoirs in rangelands and cultivated areas)
Length of road that is constructed each year and number of culverts that are place
Length of road that is maintained each year and number of culverts that are (re)placed
Besides these physical characteristics of roads, other aspects should also be studied to better quantify
the real potential for up-scaling. These aspects include technical capacity of farmers, type(s) of crop
produced, level of wealth, access to credit, access to markets, environmental state of the land and
potential upstream-downstream impacts.
60
7. Conclusions
Two general forms of road runoff harvesting can be distinguished. The first, more common form is
collecting runoff from road surfaces with roadside drains. The second form is road runoff harvesting from
a culvert, which concentrates runoff on the upstream side of a road and releases it on the lower side of
the road. Road runoff harvesting, in most cases, emanates from the tinkering mind of innovative
smallholder farmers.
The case studies (including the four additional sites that were visited) suggest that road runoff harvesting
is performing well and can indeed be considered as a welcome, complementary technology for a selected
number of smallholder farmers to cope with the unreliable and erratic rains in the drylands of subSaharan Africa. It is primarily a simple technology that can easily be adopted by farmers – provided of
course that their farm is located in the vicinity of a road. The case studies show that indigenous
knowledge is often combined with scientific expertise. Runoff is either used directly for flooding the farm
field (runoff farming) or stored for supplemental irrigation. In a second instance, more sophisticated
adaptations to runoff harvesting systems can be made, e.g. by adding water reservoirs and water
distribution tools. The technology is very flexible and can be adapted to the local conditions. These
findings are corroborated by the (sporadic) information on road runoff harvesting found in literature.
Farmers interviewed for this study are overall positive about the impacts of their road runoff systems.
Nevertheless, the technical performance, economic viability, environmental friendliness and social
acceptance differ per case. Negative environmental impacts have not been recorded. Analysis of
adoption factors points at the high establishment and maintenance costs as a critical factor.
Comprehensive (technical, economic, environmental and social) benefit-costs analysis of these and other
case studies is needed to confirm these outcomes.
The estimated potential for up-scaling road runoff harvesting in sub-Saharan Africa is large: around 2.63
million kilometres of roads are located in the drylands (rangelands and cultivated areas only). If only 25%
of these roads would be suitable for collecting runoff, still vast volumes of runoff could be harvested from
the road surface. Together with the estimates of the number of culverts along these roads, these results
suggest that roughly 2.2 million households could benefit from the additional ‘green’ (for crops) or ‘pink’
(for livestock) water flows arising from the approximately 0.5 cubic kilometre of runoff. Studies at the local
level are required to determine the feasibility of applying road runoff harvesting on a case-by-case basis.
As more and more people living in the drylands of other continents are facing water scarcity, farmers in
sub-Saharan Africa may become world leaders in upgrading rainfed agriculture with simple, low-cost
water harvesting technologies like road runoff harvesting.
61
8. Recommendations
8.1 Further research
Based on the research carried out for this thesis, the following recommendations can be made for further
research on road runoff harvesting:
•
•
•
•
•
•
•
•
•
•
Document more and different designs of road runoff harvesting systems.
Monitor runoff flows to estimate actual runoff volumes, monitor pollution of runoff, monitor crop
performance, monitor the impacts on livelihoods, the community and the natural environment.
Include all relevant technical, economic, environmental and social aspects of road runoff
harvesting.
Focus on long-term research projects: include monitoring and evaluation (M&E) activities over a
period of several years.
Do a full benefit-cost analysis of road runoff harvesting sites, including social and environmental
factors, based on a large sample size and preferably on data collected over longer periods of
time. Lare Division in Kenya could be a potential target area, because many of the hundreds of
farm ponds are known to collect runoff from roads and have already been mapped (Malesu et al.,
2006). Use GPS and GIS to determine the exact size of catchment and cultivation areas.
Further analyse the factors that lead to adoption or to non-adoption. Provide further insight into
the adoption process, for instance with regard to early and late adopters. Make an inventory of
both success stories and failures.
Study the upstream and downstream impacts of road runoff harvesting, at the community level
and at the watershed level.
Following the preliminary assessment of roads in sub-Saharan Africa presented (the present
study), do a GIS mapping study for sub-Saharan Africa on the potential of roads and culverts for
road runoff harvesting, similar to the study of Mati et al. (2006) that focused on the potential of
rainwater harvesting in Africa.
Support such a region-wide study with GIS-studies focused on smaller regions (e.g. Machakos
District, Kenya), to map in detail which areas could be used as catchment and cultivation areas.
Link the data from local case studies and GIS mapping with local data on demographic, climatic,
socio-economic, political and cultural data to determine the local potential for road runoff
harvesting.
Identify suitable funding mechanisms for up-scaling road runoff harvesting (e.g. through microcredit or merry-go-round schemes).
In addition to these research needs related to road runoff harvesting, there also seems to be a need for
standardising the definitions (and thus boundaries) of arid, semi-arid and dry sub-humid areas, as well as
drylands as a whole.
8.2 Policy-making
The outcomes of this study highlight some aspects that are also relevant for policy-makers. It is
recommended that:
62
•
•
•
•
•
•
•
Road runoff harvesting is streamlined into the policies and activities of relevant ministries, i.e.
ministries that deal with (railway and road) infrastructure, agriculture, water and the environment.
Local administrations are made aware of the opportunities of using road runoff harvesting (e.g. as
part of integrated water resources management (IWRM) plans in watersheds).
Road runoff harvesting is further promoted at supranational level, such as at the African
Ministerial Conference on Water (AMCOW).
Monitoring and evaluation (M&E) is also done at the level of policy implementation.
An (agro-) environmental impact assessment is commissioned prior to (rail) road construction or
maintenance activities, and an long-term agreement is reached with neighbouring (farmer)
communities about the management of road runoff (from roadside drains and/or culverts). On one
hand, this could help preventing erosion, gully-formation and pollution; on the other hand it may
provide farmers with extra ‘green’ flows.
Funding agents (such as the World Bank and the African Development Bank) incorporate an
agro-environmental impact assessment into their guidelines for road construction and
9
maintenance , including suggestions for socially accepted management plans that deal with road
runoff harvesting. In addition, road network evaluation and decision making tools that are
available online could be upgraded to also consider the possibilities for road runoff harvesting.
Credit facilities are put in place to allow farmers to invest in road runoff harvesting technologies
(including reservoirs, drip-irrigation kits and greenhouses).
8.3 Development and extension work
Development agents (such as inter-governmental organisations, non-governmental organisations,
networks, associations and civil society organisations) and extension workers can also be involved in the
further promotion and development of road runoff harvesting schemes. Developments agents include the
United Nations Environment Programme (UNEP), the United Nations Development Programme (UNEP),
the Food and Agriculture Organisation (FAO), World Vision International (WVI), the Southern and Eastern
Africa Rainwater Network (SearNet), and the Greater Horn of Africa Partnership (GHARP) that involves
rainwater associations located in Ethiopia, Kenya, Somalia, Tanzania and Uganda.
It is recommended that these agents:
•
•
•
•
Promote the various options of using road runoff harvesting amongst the smallholder farmers in
sub-Saharan Africa, e.g. through FAO’s Farmer Field Schools.
Incorporate road runoff harvesting as a complementary technology in their programmes, plans
and projects, e.g. in the Promoting Farmer Innovation (PFI) methodology.
Develop business plans for smallholder farmers to adopt road runoff harvesting, e.g. like the
plans WVI has developed in collaboration with local partners who provide a greenhouse/dripirrigation kit and the necessary credit. See for instance:
http://www.amirankenya.com/index.php?option=com_content&view=article&id=305
Include M&E as a standard element of projects; request the active involvement of farmers in the
M&E activities.
9
See e.g.:
http://web.worldbank.org/WBSITE/EXTERNAL/TOPICS/EXTTRANSPORT/EXTROADSHIGHWAYS/0,,contentMDK:2
0483189~menuPK:1097394~pagePK:148956~piPK:216618~theSitePK:338661,00.html
63
References
African Development Bank (AfDB) (2007) Assessment of best practices and experiences in rainwater
harvesting. Rainwater harvesting handbook. Tunis, Tunisia: AfDB.
Agarwal A. and Narain, S. (eds) (1997) Dying Wisdom: rise, fall and potential of India’s traditional water
harvesting systems. Centre for Science and Environment, New Delhi, India, 404 pages
Barron, J. and Okwach, G. (2005) Run-off water harvesting for dry spell mitigation in maize (Zea mays
L.): results from on-farm research in semi-arid Kenya. Agricutlural Water Management 74: 1-21.
Bittar, O.J. (2001) Water conservation and harvesting – Busia experience. Water Conservation,
Harvesting and Management (WCHM) in BUsia District, Kenya – A minor field study. Soil and Water
Conservation Branch, Ministry of Agriculture.
Boers, D. and Ben-Asher, J. (1982) Review of rainwater harvesting. Agricultural Water Management 5:
145-158.
Bongaarts, J. (2001) Household Size and Composition in the Developing World. Population Council., New
York, USA. Available at: http://www.popcouncil.us/pdfs/wp/144.pdf
Bouma, J.A., et al., The downstream externalities of harvesting rainwater in semi-arid watersheds: An
Indian case study. Agric. Water Manage. (2011), doi:10.1016/j.agwat.2011.02.010
Critchley, W.R.S. (1991) Looking after our land. Soil and water conservation in Dryland Africa. Ed. Olivia
Graham. Oxfam, 1991. Available at http://www.fao.org/docrep/x5301e/x5301e00.htm#Contents.
Critchley, W.R.S. and Siegert, K. (1991) Water Harvesting: A Manual for the Design and Construction of
Water Harvesting Schemes for Plant Production. FAO, Rome.
Critchley, W.R.S., Reij, C. and Turner S.D. (1992) Soil and Water Conservation in Sub-Saharan Africa:
towards sustainable production by the rural poor. IFAD, Rome and CDCS, Amsterdam.
Critchley, W.R.S., Cooke, R., Jallow, T., Lafleur, S., Laman, M., Njoroge, J., Nyagah, V. and Saint-Firmin,
E., (1999) Promoting Farmer Innovation. Nairobi: RELMA WorkShop Report no 2, Nairobi, Kenya.
Critchley, W.R.S. 2007. Working with farmer innovators. A practical guide. Technical Centre for Agricltural
and Rural Cooperation (CTA), Wageningen, The Netherlands.
Falkenmark, M. (1989)
The Massive Water Scarcity Now Threatening Africa—Why Isn't It Being
Addressed? AMBIO 18(2): 112–20.
Falkenmark, M. (1995) Land-water linkages - A synopsis. in Land and`Water integration and river basin
management. FAO Land and Water Bulletin No I : 15-16. FAO. Rome, Italy.
FAO (1986) Irrigation Water Management. Training Manual No. 3 (crop water needs). Available online at
http://www.fao.org/docrep/S2022E/S2022E00.htm. Accessed on 29-7-2012.
FAO (1989) Arid zone forestry: A guide for field technicians. FAO Conservation Guide. Available at:
http://www.fao.org/docrep/T0122E/t0122e00.htm#Contents. Accessed on 5-8-2012.
FAO (1993) Land degradation in arid, semi-arid and dry sub-humid areas: rainfed and irrigated lands,
rangelands and woodlands. Inter-governmental negotiating committee for the preparation of a
convention to combat desertification and drought (INCD). First Substantive Session, Nairobi 24 May 4 June 1993. Available at http://www.fao.org/docrep/X5308E/X5308E00.htm. Accessed on 12-82012.
FAO (1995) Irrigation in Africa in Figures – L’irrigation en Afrique en Chiffres. FAO, Rome.
FAO
(1995)
Country
Pasture/Forage
Resource
Profile.
Available
http://www.fao.org/ag/AGP/AGPC/doc/Counprof/kenya/Kenya.htm#3. Consulted on 31-1-2012.
at:
FAO (2001) Smallholder irrigation technology: prospects for sub-Saharan Africa. International Programme
for
Technology
and
Research
in
Irrigation
and
Drainage
Knowledge Synthesis Report No. 3. Roma, Italy, 2001.
Fox, P., Rockström, J. and Barron, J. (2005) Risk analysis and economic viability of water harvesting for
supplemental irrigation in semi-arid Burkina Faso and Kenya. Agricultural systems 83: 231-250.
Hatibu, N. and Mahoo, H.F. (2000a). Rainwater Harvesting for Natural Resources Management, A
planning guide for Tanzania. Technical Handbook No. 22. RELMA, Nairobi.
64
Hatibu, N., Mahoo, H. F. and Kajiru, G.J. (2000b) The role of RWH in agriculture and natural resources
management: from mitigating droughts to preventing floods. In: Rainwater Harvesting for Natural
Resources Management. Hatibu, N. and Mahoo, H. F. (eds) A planning guide for Tanzania. Technical
Handbook No. 22. RELMA, Nairobi. 58-83.
ICRAF,
(2012)
Website
of
World
Agroforestry
Centre
http://worldagroforestry.org/projects/searnet/index.php?id=67. Accessed on 30-7-2012.
(ICRAF):
IFAD (2010) Rural Poverty Report. New realities, new challenges: new opportunities for tomorrow’s
generation. International Fund for Agricultural Development (IFAD), Roma, Italy, 2010.
IUCN (Behnke, R. ed.) (2007) Kenya’s Drylands – Wastelands or an Undervalued National Economic
Resource. The World Conservation Union (IUCN), 2007.
Jungerius, P.D., Matundura, J., van de Ancker, J.A.M. (2002) Road construction and gully erosion in
West Pokot, Kenya. Earth Surface Processes and Landforms 27: 1237-1247.
Kenya National Bureau for Statistics (2012) http://www.knbs.or.ke/counties.php. Accessed on 10-8-2012.
Kenya Roads Board (2012) Website of the Kenya Roads Board. http://www.krb.go.ke/road-network/roadnetwork.html Accessed on 10-8-2012.
Kiggundu, N. (2002) Evaluation of rainwater harvesting systems in Rakai and Mbarara Districts, Uganda.
GHARP case study report. Greater Horn of Africa Rainwater Partnership (GHARP), Kenya Rainwater
Association, Nairobi, Kenya.
Malesu, M., Sang, J.K., Odhiambo, O.J., Oduor, A.R., Nyabenge, M. (2006) Hydrologic impacts of ponds
on land cover change: Runoff harvesting in Lare, Kenya. (Rainwater harvesting innovations in
response to water scarcity: The Lare experiences.) Technical Report No. 32 Nairobi, Kenya: Regional
Land Management Unit (RELMA-in-ICRAF), Netherlands Ministry of Foreign Affairs and Swedish
International Development Agency (SIDA), 41 p.
Malesu, M., Oduor, A.R., and Odhiambo, O.J. (2007) Green Water Management Handbook. Rainwater
harvesting for agricultural production and ecological sustainability. Technical Manual No. 8 Nairobi,
Kenya: World Agroforestry Centre (ICRAF), Netherlands Ministry of Foreign Affairs. 219 p.
Mati, B.M. (1993) Soil erosion and conservation activities on land affected by road drainage: a case study
of Nyeri District. In Workshop. Abstracts, 4th Land and Water Management Workshop towards
Sustainable Land Use. University of Nairobi.
Mati, B.M. (2005) Overview of water and soil nutrient management under smallholder rainfed agriculture
in East Africa. Work Paper 105. Colombo, Sri Lanka: International Water Management Institute
(IWMI).
Mati, B., De Bock, T., Malesu, M., Khaka, E., Oduor, A., Nyabenge, M., and Oduor, V. (2006) Mapping
the Potential of Rainwater Harvesting technologies in Africa: A GIS overview on development
domains for the continent and ten selected countries. Technical Manual No. 6 Nairobi, Kenya: World
Agroforestry Centre (ICRAF), Netherlands Ministry of Foreign Affairs. 116 p.
Molden, David. (Ed.) 2007. Water for food, water for life: A Comprehensive Assessment of Water
Management in Agriculture. London, UK; Colombo, Sri Lanka: Earthscan; IWMI. 645p.
Mugerwa, N. (2007) Rainwater harvesting and rural livelihood improvement in banana growing areas of
Uganda. Master’s Thesis, Department of Water and Environmental Studies, Linköping University.
Muhammad, L., Njoroge, K., Bett, C., Mwangi, W., Verkuijl, H., De Groote, H. (2003) The Seed Industry
for Dryland Crops in Eastern Kenya. Mexico, D.F.: CIMMYT and Kenya Agricultural Research
Institute (KARI)
Murray, S., Bruke, L., Tunstall, D. and Gilruth, P. (1999). Drylands population assessment II. Draft
November, 1999. World Resources Institute and UNDP Office to Combat Drought and Desertification.
Mutiga, J.K., Zhongbo, S, and Woldal, T. (2011) Impacts of agricultural intensification through up-scaling
of suitable rainwater harvesting technologies in the upper Ewase Ngiro North basin, Kenya. Hydrol.
Earty Syst. Sci. Discuss. 8: 2477-2501.
Mutunga, K., and Critchley ,W. (2001) Farmers' initiatives in Land Husbandry: promising technologies for
the drier areas of East Africa. Regional Land Management Unit/Sida. Nairobi. 108 pp.
Ngigi, S.N. (2003a) Rainwater Harvesting for Improved Food Security: promising technologies in the
Greater Horn of Africa. Kenya Rainwater Association for the Greater Horn of Africa Rainwater
Partnership.
65
Ngigi, S.N. (2003b) What is the limit of up-scaling rainwater harvesting in a river basin? Physics and
Chemistry of the Earth. 28: 943-956.
Ngigi, S.N., Savenije, H.H.G., Rockström, J., Gachene, C.K. (2005) Hydro-economic evaluation of
rainwater harvesting and management technologies: Farmers investment options and risks in semiarid Laikipia district of Kenya. Physics and Chemistry of the Earth 30 (2005): 772–782.
Ngigi, S.N., Savenije, H.H.G., Gichuki, F.N. (2007) Land use changes and hydrological impacts related to
up-scaling of rainwater harvesting and management in upper Ewaso Ng'iro river basin, Kenya.
Ngigi, S.N. (2008) Technical evaluation and development of low-head drip irrigation systems in Kenya.
Irrigation and drainage. 57: 450-462.
Ngigi, S.N. (2009) Climate Change Adaptation Strategies: Water Resources Management Options for
Smallholder Farming Systems in Sub-Saharan Africa. The MDG Centre for East and Southern Africa,
The Earth Institute at Columbia University, New York. 189p.
Nissen-Petersen, E. (2006) Water from roads. A handbook for engineers and technicians on harvesting
rainwater from roads. DANIDA 2006.
Nissen-Petersen,
E.
(2010)
Video
on
road
runoff
harvesting.
http://www.thewaterchannel.tv/es/videos/categorias/viewvideo/631/water-harvesting/water-fromroads. Accessed on 29-7-2012.
Opiyo, F.E.O., Mureithi, S.M. and Ngugi, R.K. (2011) The Influence of Water Availability on Pastoralist’s
Resource Use in Mwingi and Kitui Districts in Kenya. Journal of Human Ecology. 35(1): 43-52.
Oweis, T., Hachum, A., and Kijne, J. (1999) Water harvesting and supplemental irrigation for improved
water use efficiency. SWIM Paper No. 7. IWMI, Colombo, Sri Lanka.
Pretty, J., Toulmin, C. and Williams, S. (2011) Sustainable Intensification: Increasing Productivity in
African Food and Agricultural Systems. International Journal of Agricultural Sustainability. 9 (1).
Qiang, Z. and Yuanhong, L. (2003) Drought-Proofing villages in Gansu Province. LEISA magazine ,
Volume 19 no2, ILEIA, The Netherlands
Roads
Fund
Board
(2012).
Website
Roads
http://www.roadsfundtz.org/web/roadnetworks.asp. Accessed on 11-8-2012.
Fund
Board,
Rockström, J. (1999) On-farm Green Water Estimates as a Tool for Increased Food Production in Water
Scarce Regions. Phys. Chem. Earth (B). 24(4): 375-383.
Rockström, J. (2000) Water Resources Management in Smallholder Farms in Eastern and Southern
Africa: An Overview. Physics and Chemistry of the Earth, 25 (3): 275-283.
Rockström, J. and Falkenmark, M. (2000) Semiarid crop production from a hydrological perspective: gap
between potential and actual yields. Critical Reviews in Plant Sciences, 19: 319–346.
Rockström, J., Barron and Fox, P. (2003) Water Productivity in Rain-fed Agriculture: Challenges and
Opportunities for Smallholder Farmers in Drought-prone Tropical Agroecosystems. In: Kijne, J.W. ,
Barker, R. and Molden, D., , CAB International.
Sachdeva, S.N., Sharma, U. (2008) Potential of Road Rainwater Harvesting in Urban Areas. 3rd IASME /
WSEAS Int. Conf. on WATER RESOURCES, HYDRAULICS & HYDROLOGY (WHH '08), University
of
Cambridge,
UK,
Feb.
23-25,
2008.
Available
at
http://www.wseas.us/elibrary/conferences/2008/uk/WHH/WHH-04.pdf.
Safriel, U., Z. Adeel, D. Neimeijer, J. Puigdefabregas, R. White, M. Lal, M. Winslow, J. Ziedler, S. Prins,
E. Archer, en C. Koning. 2002. Dryland Systems (Ch. 22): 625-662. Millennium Ecosystem
Assessment. Island Press, New York.
Schwilch, G., Bestelmeyer, B., Bunning, S., Critchley, W., Herrick, J., Kellner, K., Liniger, H.P.,
Nachtergaele, F., Ritsema, C.J., Schuster, B., Tabo, R., van Lynden, G. and Winslow, M. (2011)
Experiences in monitoring and assessment of sustainable land management. Land Degrad. Develop.
22: 214–225.
Shaxson, F. and Barber, R. (2003) Optimizing Soil Moisture for Plant Production. FAO Soils Bulletin 79.
Rome, 2003. Available at http://www.fao.org/docrep/006/y4690e/y4690e00.htm#Contents.
SIWI (2001) Water harvesting for upgrading of rainfed agriculture: Problem analysis and research needs.
Eds. Falkenmark M, Fox P, Persson G, Rockström J. SIWI report 11, Stockholm, Sweden, (pp41-79).
Stockholm Environment Institute (Barron, J. ed) (2009) Rainwater Harvesting: a Lifeline for Human WellBeing. United Nations Environment Programme.
66
Svendsen, M., Ewing, M., Msangi, S. (2009) Measuring irrigation performance in Africa. International
Food Policy Research Institute (IFPRI) Discussion Paper 00894. IFPRI, Environment and Production
Technology Division.
Tiffen, M., and Mortimore, M. (1994) Environment, Population growth and Productivity in Kenya: A Case
Study of Machakos District. IIED Drylands Networks Programme Issues Paper:27.
Tiffen , M., Mortimore, M. And Gichuki, F. (1994) More People, Less Erosion. Environmental recovery in
Kenya. ACTS Press, Nairobi, Kenya, and Overseas Development Institute, London, 1994.
Thornton, P.K., P.G. Jones, T.M. Owiyo, R.L. Kruska, M. Herero, P. Kristjanson, A. Notenbaert, N. Bekele
and Co-authors (2006) Mapping Climate Vulnerability and Poverty in Africa. Report to the Department
for International Development, ILRI, Nairobi, 200 pp.
Tuitoek, D.K., Owido, S.F.O., China, S.S., Wanjama J.K. (2001) Transfer and adoption of water
harvesting technologies for domestic and livestock use in Lare Division, Nakuru District. Unpublished
paper.
UNEP (1992) World atlas of desertification. United Nation Environment Programme (UNEP) and Edward
Arnold.
UNEP (1997) Source Book of Alternative Technologies for Freshwater Augmentation in Latin America
and the Caribbean. IETC Technical Publication Series by UNEP International Environmental
Technology Centre, Osaka/Shiga, Japan, 1997.
UNEP (2003) Technology Transfer: The Seven “C”s for the Successful Transfer and Uptake of
Environmentally Sound Technologies. International Environmental Technology Centre (IETC), United
Nations Environment Programme (UNEP). Osaka, Japan.
Vlek, P.L.G., Bao Le, Q. and Tamene, L. (2008) Land Decline in Land-Rich Africa: A Creeping Disaster in
the Making. Consultative Group on International Agricultural Research. Centre for Development
Research (ZEF), University of Bonn, Germany.
WOCAT (2005) Online database, available at www.wocat.org.
WOCAT (Liniger H. and Critchley, W. eds) (2007) where the land is greener: case studies and analysis of
soil and water conservation initiatives worldwide. CTA, FAO, UNEP, CDE, Bern
WOCAT (2000) WOCAT Questionnaire on SLM Technologies. A framework for Evaluation of Soil and
Water Conservation. WOCAT Centre for Development and Environment, University of Bern,
Hallerstrasse 12, CH-3012, Berne, Switzerland.
Zeedyk, B. (2006) Water harvesting from low-standard rural roads. Joint publication of The Quivira
Coalition, Zeedyk Ecological Consulting, LLC, The Rio Puerco Management Committee – Watershed
Initiative, and the New Mexico Environment Department – Surface Water Quality Bureau, April 2006.
Ziadat, F.M., Mazahreh, S.S., Oweis, T.Y., Bruggeman, A. (2006) A GIS-based Approach for Assessing
Water Harvesting Suitability in a Badia Benchmark Watershed in Jordan. 14th International Soil
Conservation Organization Conference. Water Management and Soil Conservation in Semi-Arid
Environments. Marrakech, Morocco, May 14-19, 2006 (ISCO 2006)
67
Annex I Categorisation of WOCAT data
Categorisation of the WOCAT Questionnaire for SLM Technologies according to four elements of the TEES-test
(Technical, Economic, Environmental and Social) as well as General information on a Technology. The subcategories of each element are also indicated in the last column.
PART 1: GENERAL INFORMATION
1.1 Specialist*
1.2 SLM technology*
1.2.1 Common name*
1.2.2 Local name*
1.2.3 Part of watershed?*
1.2.4 Approach*
1.3 Area information
1.3.1 Area definition*
1.3.2 Coordinates*
PART 2: SPECIFICATION OF SLM TECHNOLOGY
2.1 Description
2.1.1 Definition*
2.1.2 Main characteristics*
2.1.3 Photos*
2.1 Purpose and classification
2.2.1 Land use problems*
2.2.2 Characterisation and purpose
2.2.2.1 Land use type*
2.2.2.2 Conservation measures*
2.2.2.3 Goals*
2.2.2.4 Land degradation type*
2.2.2.5 Causes of land degradation
2.2.2.6 Measures against land degradation
2.3 Status
2.3.1 Origin
2.3.2 Technical knowledge required*
2.4 Technical drawing*
2.5 Technical specifications
2.5.1 Agronomic measures*
2.5.1.1 Type and lay-out*
2.5.1.2 Activities, inputs and costs*
2.5.2 Vegetative measures
2.5.2.1 Type and layout
2.5.2.2 Activities, inputs and costs
2.5.3 Structural measures
2.5.3.1 Type and layout
2.5.3.2 Activities, inputs and costs
2.5.4 Management measures
2.5.4.1 Type and layout
2.5.4.2 Activities, inputs and costs
2.6 Overview of costs
2.6.1 Establishment
2.6.2 Most determinate factors
2.7 Natural environment
2.7.1 Average rainfall*
2.7.2 Agro-climatic zone*
2.7.3 Thermal climate
2.7.4 Growing seasons
2.7.5 Climate tolerance of Technology
2.7.6 Altitudinal zonation*
2.7.7 Landforms*
2.7.8 Slopes*
2.7.9 Soil depth*
2.7.10 Soil texture*
2.7.11 Soil fertility*
2.7.12 Topsoil organic matter*
Input TEES- test
Sub-category
General
General
General
General
General
General
General
General
General
None
None
None
None
None
None
None
None
None
NA
General
General
General
NA
Technical
Technical
Technical
Technical
Technical
Technical
Technical
Technical
NA
Social
Technical
Technical
NA
Technical
Technical
Technical / Economic
Technical
Technical
Technical / Economic
Technical
Technical
Technical / Economic
Technical
Technical
Technical / Economic
NA
Economic
Economic
NA
Technical
Technical
Technical
Technical
Technical
Technical
Technical
Technical
Technical
Technical
Technical
Technical
NA
None
None
None
NA
Purpose
Purpose
Purpose
Measures
Purpose
Purpose
Purpose
Measures
NA
Origin
Knowledge required
Measures
NA
Measures
Measures
Measures / Input (resp.)
Measures
Measures
Measures / Input (resp.)
Measures
Measures
Measures / Input (resp.)
Measures
Measures
Measures / Input (resp.)
NA
Costs
Costs
NA
Conditions
Conditions
Conditions
Conditions
Conditions
Conditions
Conditions
Conditions
Conditions
Conditions
Conditions
Conditions
68
2.7.13 Soil drainage / infiltration*
2.7.14 Soil water storage capacity
2.7.15 Ground water table
2.7.16 Availability of surface water
2.7.17 Water quality (untreated)
2.7.18 Biodiversity
2.8 Human environment and land use
2.8.1 Land users applying Technology*
2.8.2 Population density*
2.8.3 Annual population growth
2.8.4 Land and water ownership and rights*
2.8.5 Level of wealth
2.8.6 Significance of off-farm income
2.8.7 Access to services and infrastructure
2.8.8 Conditions crop land
2.8.8.1 Market orientation*
2.8.8.2 Land use tools*
2.8.8.3 Type of cropping system
2.8.8.4 Water supply
2.8.8.5 Livestock
2.8.8.6 Size of cropland*
2.8.9 Conditions grazing land
2.8.9.1 Market orientation
2.8.9.2 Type of grazing system
2.8.9.3 Water supply
2.8.9.4 Livestock density
2.8.9.5 Size of grazing land
2.8.10 Conditions forest / woodland
2.8.10.1 Market orientation
2.8.10.2 Type of forest / woodland
2.8.10.3 Purpose
2.8.10.4 Size of forest / woodland
2.8.11 Conditions other land
2.8.11.1 Types
PART 3: ANALYSIS OF THE SLM TECHNOLOGY
3.1 Impacts: benefits and disadvantages
3.1.1 On-site benefits
3.1.1.1 Production and socio-economic benefits*
3.1.1.2 Socio-cultural benefits*
3.1.1.3 Ecological benefits*
3.1.1.4 Other benefits*
3.1.2 Off-site benefits*
3.1.3 On-site disadvantages
3.1.3.1 Production and socio-economic
disadvantages
3.1.3.2 Socio-cultural disadvantages
3.1.3.3 Ecological disadvantages
3.1.3.4 Other disadvantages
3.1.4 Off-site disadvantages
3.1.5 Contribution to wellbeing
3.2 Economic analysis
3.2.1 Benefits vs establishment costs*
3.2.2 Benefits vs maintenance costs*
3.3 Acceptance or adoption
3.3.1 Acceptance with external material support*
3.3.1.1 Number of land user families*
3.3.2 Spontaneous adoption*
3.3.2.1 Number of land user families*
3.3.2.2 Adoption trend*
3.4 Concluding statements
3.4.1 Majors strengths of Technology
3.4.2 Major weaknesses of Technology*
* Questions that are part of the Summary Questionnaire
Technical
Technical
Technical
Technical
Technical
Environmental
NA
Social
Social
Social
Social
Economic
Economic
Economic
NA
Economic
Economic / Social
Economic
Economic
Economic
Economic / Technical
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Conditions
Conditions
Conditions
Conditions
Conditions
Biodiversity
NA
Conditions
Conditions
Conditions
Conditions
Conditions
Conditions
Conditions
NA
Conditions
Conditions / Conditions
Conditions
Conditions
Conditions
Conditions / Conditions
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Economic
Social
Environmental
General
Social / Environmental
NA
Economic
NA
NA
Benefits
Benefits
Benefits
NA
Benefits
Disadvantages
Disadvantages
Social
Environmental
General
Social / Environmental
Social
NA
Economic
Economic
NA
Social
Social
Social
Social
Social
NA
General
General
Disadvantages
Disadvantages
NA
Disadvantages
Benefits
NA
Costs, Benefits
Costs, Benefits
NA
Adoption
Adoption
Adoption
Adoption
Adoption
NA
NA
NA
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