Climate Variability and Change: vulnerability of communities in Senqu ecological zone, Lesotho.
Deepa Pullanikkatil1, Caxton Henry Matarira2 and Motsomi Maletjane3
1
Lerotholi Polytechnic; 2 National University of Lesotho; 3Lesotho Meteorological Services.
Abstract:
This study analyses climate variability and change in the Senqu valley in Lesotho and provides
information on impacts of climate change on agriculture and water supply for communities living
in the Senqu valley. Climate change studies have been focused at global, continent and regional
levels and this study scales down to country and community level. The study analysed 30 years of
data for rainfall and temperature for the Senqu valley.
The results show that temperatures are on a rising trend for Senqu valley ad winter rainfall is on
decreasing trend, while summer and spring rainfall is showing and increasing trend. This has
implications for agriculture and water supply for the community. The study recommends amongst
others to improve water storage capacity and change agricultural practices to adapt to changing
climate. Further areas for research are also identified.
Keywords: Climate change, climate variability, Senqu, Lesotho, vulnerability, adaptation.
Introduction
Africa is said to be one of the most vulnerable regions in the world to climate change (WWF,
2008). According to the IPCC IV Technical Paper (2008) on “Climate Change and Water”, a
decrease of water resources are expected due to climate change in Southern Africa. Climate
change can affect and change water quantity and water quality. Precipitation changes will impact
on water quantity while temperature changes and extreme variations in rainfall will affect water
quality by altering sediment load, causing thermal pollution and making changes in chemical
composition of water (IPCC IV technical report, 2008). This change in water quality and quantity
will, in turn, affect communities. Food security, agricultural yields and stability and access to
water are expected to be negatively impacted.
There is a need to scale down the studies on climate change to local levels. In response to this
need, this study focuses on the Orange/Senqu River catchment area in Lesotho. The study
analyses temperature and rainfall variability and trends over 30 years in the Orange/Senqu
ecological zone. The study also assesses how these changes will impact agriculture and water
availability for communities living in the area.
Background
The study area is limited to the Orange/Senqu river basin within Lesotho (Figure 1). Figure 2
shows the Senqu livelihood zone.
Figure 1 Rivers in Lesotho
Source: fao.org accessed 2008
Figure 2 Senqu River Valley
Objectives of the study
The specific objectives of the study are:
1. To analyse temperature and rainfall changes in Orange/senqu region and Lesotho as a
whole for thirty years (1961-80 and 1971-90)
2. To assess how temperature and rainfall trends will impact
a. Agriculture
b. Water supply for communities within the area.
3. To identify further research areas.
Literature Review
The Orange River rises in the Lesotho Highlands 3300m above sea level. The river basin is the
largest watershed in South Africa, and the Orange is the largest river in Africa south of the
Zambezi. Approximately 64% of the one million square kilometers that form the catchment area
lie within South Africa (Table 1). The remainder falls within Botswana (8%), Namibia (25%)
and Lesotho (3%). The river originates in the Drakensberg range in Lesotho and stretches over
2200 km westwards to the south Atlantic (Nakayama et. al.2003).
Country
South Africa
Namibia
Botswana
Lesotho
Total area of Area
of
the Percent of total
country (km2)
Country within area of country
Orange
river
basin (km2)
1,221,040
575,769
47
824,900
219,249
27
581,730
71,000
12
30,350
30,350
100
Table 1 Area of Orange river basin in countries
Source: FAO, 1997
% of total area
of basin
64
25
8
3
Hundred per cent of land area of Lesotho falls within the area of the Orange river basin as the
three catchments of the Orange River basin lie within Lesotho. These are the Senqu, Makhaleng
and Mohokare. Senqu is the largest river and has a drainage area within Lesotho of 20,847 square
km and a mean annual runoff at the point of exit of 128 cubic meters /second. Mohokare has a
drainage area within Lesotho of 6,890 square km and an average annual discharge rate of 35.4
cubic meters / second at the point of exit. Makhaleng, which is the smallest river, registers a mean
annual runoff of 16.7 cubic meters / second at the lowest point, and covering a drainage area of
2,911 square km. It is estimated that Lesotho has a total 5,925 million cubic meters of static and
341 million cubic meters of renewable ground water resources (TAMS 1996).
The Orange basin is characterized by extremely variable rainfall, ranging from around 2000 mm
per year in the Lesotho Highlands to 50 mm per year near its mouth. The climatic variability
within the Orange Basin produces large differences in the distribution of water resources within
it. Lesotho, constituting only 3% of the basin area, contributes approximately 45% of its runoff,
yet Botswana does not contribute any runoff to the basin (FAO, 1997). This has impacts on water
demand.
Globally, a country is categorized as “water-stressed” if its annual renewable freshwater supplies
are between 1000 and 1700 cubic meters per capita and “water-scarce” if its renewable freshwater
supplies are less than 1000 cubic meters per capita (World Bank 2000). At the current population
growth rate and climate, and a fresh water availability of 5.4 cubic km per annum, it is estimated
that Lesotho will enter a water stress period of less than 1700 cubic meters per capita per year by
2019, and a water scarcity period of less than 1000 cubic meters per capita per year by year 2062
(TAMS 1995). Under climate change scenarios which predict lower surface and sub-surface
runoff, this would mean increased water scarcity for both households and livestock. A host of
other economic activities are likely to be affected. Reduced precipitation in Lesotho under climate
change translates into reduced runoff in the catchment areas of the biggest rivers in southern
Africa.
Water demand in Lesotho is largely for households, followed by manufacturing and services, and
then agriculture, livestock, traditional uses, mining and lastly crop irrigation.
Agriculture
Crop irrigation
Livestock
19.27
0.40
18.87
Traditional
18.87
Mining
1.00
Manufacturing and services
21.00
Households
24.00
Table 2 Water Use in Lesotho 2000 (million cubic meters)
Source: Lange, Mungatana and Hassan (2007)
Land use changes already impact the terrestrial water cycle and will continue to do so in the next
century. They cause a marked increase in runoff (Jackson et. al. 2005). Studies are required to
investigate how these changes in cropland establishment and abandonment, and climate change,
modify the regional runoff patterns. Long term runoff changes result from the balance of
precipitation and evapotranspiration. Runoff change is driven mainly by climate trends and
variability alone.
The interannual runoff variability in Africa and the spatial distribution of trends in runoff are
related to rainfall and surface fractional area of croplands (Jackson et. al. 2005). The expansion of
croplands produces a remarkable increase in runoff. The largest increase in runoff is located in
mountain areas where pronounced increases in annual precipitation are observed. A decrease in
runoff accompanied by an increase in evapotranspiration, has important implications for both
soil-water storage and plant growth. Such a decrease in soil moisture can exert negative
feedbacks on vegetation growth, especially in water stressed ecosystems.
There is, generally, a cause-and-effect relationship between rainfall and the resulting runoff.
However, such a relationship is not a direct one. A lot of other complex aspects come into play.
These include evapotranspiration, interception, depression storage, infiltration and soil-moisture
deficiency. Other aspects are the characteristics of the catchments: namely, the size, slope, shape,
altitude, subsurface geology and climate.
Methodology
The methodology followed in this study was a combination of literature review , followed by
analysis of climate data to identify historic trends. Data from 1961 to 2004 were analysed for
temperature and precipitation. Data for entire Lesotho was analysed and data for Senqu river
valley which composed of information from three meteorlogical stations namely Ha Nohana,
Quthing and Seaka were anlysed specifically to generate graphs for the Senqu region.
Furthermore, climate change modeling was done using Magicc Scengen. Data from the following
models were used in Magic Scengen to generate scenarios:
CSM 98,
ECH 395,
ECH 498,
GFDL 90,
HAD 297,
HAD 300.
Results
Instrumental climate data are available for a few sites in Lesotho, from the middle of the
twentieth century. Climate data was analyzed to identify historical trends. Figure 3 shows
temperature trends over whole of Lesotho.
Figure 3 Mean temperatures over thirty years in Lesotho
The annual temperature for the whole country has increased by 0.8 OC from 1967 to 2006 (figure
3). The average rate of warming over this period is about 0.05O C per decade. Figure 4 shows the
maximum and minimum temperature trends over the Senqu River Valley. Both temperatures
show an increasing trend over the period of instrumental record.
Figure 4 Annual maximum and minimum Temperatures for Senqu River Valley
Further analyses were carried out to detect any trends in temperature for each of the threemonthly seasons, namely; June-July-August (winter), September-October-November (spring),
December-January-February (summer) and March-April-May (autumn).
Figure 5 Seasonal Temperatures for Senqu valley
Winter temperatures show a higher increasing trend although this trend is common to all the
seasons. Therefore it may be concluded with certainity that temperatures are on an increasing
trend for all seasons. Next, rainfall data was analysed and results plotted. Mean rainfall for each
season was calculated based on thrity year daya and anomalies from the mean were plotted.
Figure 6 shows anomalies for winter rainfall from mean.
Figure 6 Winter Rainfall anomalies in Senqu Valley
The analysis also brought out historical episodes related to droughts and flood events. The
instrumental record of rainfall for the same period shows a different trend (Figure 6). It
demonstrates the erratic nature of annual rainfall over Senqu agro ecological zone. Year-to-year
variability has been large (+/- 30 per cent) and has shown little sustained trend. Extreme rainfall
events during winter were registered in 1961/62, 1963/64 and 1974/75 when rainfall was above
40% of mean rainfall for the thirty year period. Severe droughts were experienced in 1962/63,
1964/65 and 1977/78 when rainfall was below 30% of mean.
Figure 7 shows rainfall anomalies during spring. The years 1976/77 and 1988/89 received rainfall
in excess of 100% of normal rainfall. On the other hand, the years 1965/66 and 1981/82 recorded
rainfall which was below 75% of normal.
Figure 7 Rainfall anomalies in spring
Results of the analysis of the summer rainfall are shown in shown in Figure 8.
Figure 8 Rainfall anomalies for summer
Notable excessive rainfall was received in 1975/76 when rainfall was over 200% of normal. Least
rainfall was received during summers of 1982/83, with less that 200% of normal.
Figure 9 Rainfall anomalies during autumn
During autumns of 1960/61 and 1961/62 rainfall was in excess of 150% of mean rainfall
calculated over 1961-90. In the 1969/70 autumn season, less than 125% of mean value was
received.
The extreme rainfall episodes are summarised and tabulated under Table 3.
Months
JJA (winter)
SON (spring)
Years of excess %
increase
rainfall
from from Mean
Mean
1961/62
+45%
1963/64
+60%
1974/75
+50%
1979/80
+40%
1961/62
1963/64
1974/75
1976/77
1978/79
1986/87
1987/88
1988/89
1989/90
+46%
+60%
+49%
+112%
+75%
+57%
+75%
+110%
+67%
Years
of
reduced rainfall
from Mean
1962/63
1964/65
1977/78
1978/79
1980/81
1965/66
1968/69
1973/74
1978/79
1979/80
1980/81
1981/82
1984/85
%
reduction
from Mean
-40%
-35%
-37%
-30%
-31%
-80%
-45%
-50%
-60%
-55%
-75%
-80%
-60%
DJF (summer)
1962/63
1966/67
1971/72
1973/74
1974/75
1976/77
1987/88
+125%
+175%
+100%
+175%
+250%
+60%
+60%
1963/64
1964/65
1967/68
1969/70
1972/73
1974/75
1982/83
1983/84
1985/86
1986/87
1986/8
1989/90
1965/66
1969/70
1978/79
1979/80
1982/83
1983/84
1984/85
1985/86
1986/87
MAM (autumn)
1960/61
+180%
1961/62
+175%
1962/63
+80%
1966/67
+120%
1968/69
+65%
1970/71
+110%
1975/76
+150%
1977/78
+120%
1987/88
+110%
1989/90
+85%
Table 3 Extreme rainfall episodes in Senqu valley
-50%
-80%
-140%
-80%
-100%
-55%
-200%
-140%
-100%
-150%
-150%
-70%
-105%
-130%
-90%
-100%
-60%
-50%
-80%
-115%
-60%
These results are in line with what Climatic Research Unit of East Anglia University (Hulme M,
1996) has said about Southern Africa as a whole. According to Hulem M, “In the region of
southern Africa represented by the twelve nations of SADC, a similar rate of warming has been
observed during the present century. ……Rainfall in the region is variable from year-to-year and
droughts have always occurred from time-to-time. The last twenty years, however, have seen a
trend towards reduced rainfall and, during the early 1990s, two or three serious droughts
occurred. The decade 1986-95, as well as being the warmest this century, has also been the
driest.”
The next section discusses Climate Change scenarios and what they predict for seasonal rainfall
patterns.
Seasonal Rainfall Projections for Lesotho
Climate change scenarios were created using trend projection from the Global Circulation
Models-down scaled models and the Magicc Scengen. The study downscaled outputs from GCM
models, i.e. the use of methods to interpolate model outputs from the relatively coarse grid sizes
that GCM’s currently utilize (typically cells of side 2 to 3 degrees latitude and longitude) to
higher spatial resolution. Once the output was downscaled, the study looked at possible change in
rainfall patterns and amounts, and temperatures, compare possible future scenarios with current
conditions, and used these as a basis for identifying the region which would be affected by
climate change. For looking at different scenarios of climate change to 2100, the variables used
are the diurnal temperature range, precipitation and average daily temperature on a monthly basis.
The climate change scenarios are made up of permutations of atmospheric-Ocean General
Circulation Models (HadCM3, and ECHam4) and three SRES scenarios (A1F1, A2 and B2).
Details of the SRES scenarios can be found in IPCC (2000).
Figure 10 shows different trends in seasonal rainfall. While the SON and DJF seasons show an
increase towards 2100, the winter seasons, MAM and JJA are projected to have decreasing
rainfall for the same period. A greater increase in SON implies that rainy seasons will set in
earlier, or that they will have isolated heavy storms. A lower increase would also imply either
lower rainfall amounts in middle of the rainy season, or intense dry spells. Both situations will
have negative impact on the amount of runoff, and hence water resources. Dry spells are often
accompanied by higher temperatures, leading to higher evapotranspiration.
Figure 10 Seasonal rainfall projections for Lesotho
Furthermore, predictions from various climate models are also congruent to the results obtained
from figures 7,8,9 and 10.
Source : www.knmi.nl/africa_scenarios/Southern_Africa/
Figure 3 Climate Change models predictions of seasonal variations in Rainfall
According to Figure 11, rainfall for South Eastern south Africa and Lesotho is reducing for winter
while increasing for spring and summer. This will have impacts on the Senqu valley and
community living within the Senqu valley. The next section discusses these impacts.
Discussion
This study analyzed 30 year data (1961-1980 and 1971-90) and collated the extreme events of
rainfall in Table 3. Analysis of temperature data revealed that temperatures are on a general
increasing trend in Lesotho (0.76degC increased over 30 years 1961-90). Senqu valley
temperatures and precipitation data were analyzed separately and the study found that minimum
temperatures for winter are increasing in Senqu region and seasonal rainfall is also showing
trends of changing. Winter rainfall is seen to decrease while summer and spring rainfall is
increasing.
The impacts of warmer temperatures on agriculture is well documented and is said to alter the
distribution of agro ecological zones.(FAO, 1997). Highlands in Lesotho may become more
suitable for annual cropping due to increased temperatures (and radiation) and reduced frost
hazards. Conversely, in some lowland areas, high temperature events may affect some crops.
Growth is hindered by high temperatures and plant metabolism begins to break down for many
cereal crops above 40OC. The effects of stress are related to the growth stage. Flowering is often
the most sensitive period. Warming tends to accelerate plant growth, reducing the length of the
growing season. If growth is accelerated during the period in which the grain is filling, the quality
of yield may decrease.
Higher temperatures also effect water resources by increase in the atmospheric demand for
moisture, i.e., potential evapotranspiration (PE). Changes in PE per degree of warming can be an
increase of up to 100 mm in climates typical of semi-arid Africa, depending on changes in
radiation and wind (Hulme1996).
The frequency distribution of temperature, rainfall and other climatic elements may change.
Within current growing season, for instance, an increase in the intensity of rainfall would
accelerate soil erosion. Rainfall that is more patchy and occurring with less regularity would
exacerbate water stress. Between wet seasons, weather could become more variable, with more
intense and persistent droughts and heat
Adaptation strategies for the agricultural sector
Adaptation involves adjustments in social and economic activities to enhance their viability and
to reduce their vulnerability to climate. It represents a practical means of accommodating current
climatic variability and extreme events as well as adjusting to longer term climatic change. The
government should encourage crop diversification and substitution. Skills transfer in seed
selection, storage and use of on-farm seeds, particularly varieties that are well adapted to harsh
environments, should be one of the priorities. The government should avail to rural farmers,
improved seeds. Farmers should be encouraged to use indigenous varieties.
The other critical strategy is the strengthening of community capacity to manage rural water
systems. There is need to prioritize small holder farmers, including encouragement of appropriate
gravity techniques, using water harvesting , water management and irrigation techniques as a
supplement to rain fed agriculture wherever possible and appropriate.
Farmers should be encouraged to incorporate conservation techniques, as well as water
management and controls, as central parts of their farming systems. This includes helping farmers
to adopt watershed management approaches, water retention, harvesting, and distribution and
control practices. They should incorporate conservation and sustainable farming practices (e.g.
terracing, contouring, trees, zero/minimum tillage etc.) into farming systems, and rehabilitate
degraded lands.
According to a study by Seo, Sungno Niggol and Mendelsohn, Robert, 2007, “A survey of over
5,000 livestock farmers in 10 countries reveals that the selection of species, the net income per
animal, and the number of animals are all highly dependent on climate. As climate warms, net
income across all animals will fall, especially across beef cattle. The fall in net income causes
African farmers to reduce the number of animals on their farms.” The authors argue that farmers
may tend to keep sheep and goats rather than cattle when their incomes fall. Therfore, small farms
may survive better than large farms specialising in beef cattle.
This can be useful information for Lesotho which have smaller livestock famers. Accordign to the
authors, “Livestock operations will be a safety valve for small farmers if warming or drought
causes their crops to fail.”
Next, we discuss adaptation strategies for water supply within communties in the wake of climate
change.
Adaptation in the water sector
The main legislation regarding water resource is the Water Resources Act of 1978 (Kingdom of
Lesotho 1978) It establishes that any use other than domestic use requires a water permit, and
that domestic use has priority over other uses. The assignment of a permit does not include any
guarantee of current or future availability of the assigned water. There is no mention of catchment
organizations. Water inspectors are responsible for the implementation of the law, implying that
the resource is managed by the ministry of Natural resources. One of the first basin institutions in
the region is the Orange-Senqu River Basin Commission (ORASECOM 2008) in 2000, which
serves as the technical advisor on matters relating to the development and utilization of the water
resources.
In 1999 Lesotho’s National Environmental Policy was approved. The policy identified “periodic
prolonged droughts and scarcity of water for agriculture” and “pollution of land and water
courses” as being among the main environmental problems. The first of its guiding principles of
the water resources management is public participation. It recognizes that “involvement of
stakeholders contributes to the efficiency, sustainability and success of water projects”. Among
other strategies identified for water resources management is the promotion of research and
conservation of shared watercourses systems and resources.
Climate change is the only issue identified for which the need for adaptive response is recognized
and included in the policy. It is recognized that there is need for mainstreaming climate change in
all developmental plans. One of the strategies envisaged is the “drawing up of contingency plans
to respond to the impacts of climate change on water resources, agriculture and other economic
sectors.
Adaptation may be improved by improving collection of water by means such as rainwater
harvesting. This will also help communities adapt to drier climates and droughts if storage
capacities for rainwater harvesting tanks are substantial enough to last several months demand for
water.
Conclusion
In view of the current climate variability and the projected decrease in rainfall in the coming
decades, as well as projected increases in temperature which will have negative impacts on future
available water resources to the Senqu communities, it is imperative that Southern African
governments take steps to adapt to the projected climatic conditions. There is a strong need for an
integrated approach for assessing adaptation options. We need to prepare for changing climatic
hazards by reducing vulnerability, by developing monitoring capabilities and by enhancing the
responsiveness of the agricultural sector to climate change.
This study gives information on climate variability and change and possible impacts for
agriculture and water supply. The recommendations from the study are :
1.
In order to meet the challenges posed by climate variability and possible climate change,
there is need to develop adequate water storage facilities for communities in Senqu valley. This
may include rainwater harvesting tanks large enough to store water for the months where rainfall
is expected to reduce.
2.
Wetlands conservation for flood control and soil erosion control will help in adapting to
extreme rainfall events.
3.
Communities dependant on agriculture as their livelihood will need to adapt to changing
climate. This may be by form of small livestock farming to augment their crops, and use of
drought resistant seeds to withstand the extreme weathers and increasing temperature. Moreover,
changes in planting times and also changes in crops varieties are to be made to suit the changing
climate.
Further research needs to be done on
1.
how agriculture can adapt to the changing climate of Senqu valley region.
2.
local level research on community level adaptation techniques including indigenous
knowledge in climate change adaptation.
The country also needs to adapt and be prepared for climate variabilities. As Hulme M, 1996 puts
it, “The clearest objective at present is to prepare for changing climatic hazards by reducing
vulnerability, by developing monitoring capabilities and by enhancing the responsiveness of the
agricultural sector to forecasts of production variations and food crises. As for general
development assistance, such activities are already justified by the present state of vulnerability to
climatic hazards in Africa. However, climate change is likely to alter the distribution of climatic
hazards, most notably drought, floods, heat waves, and frost. Enhanced preparedness is thus a
direct response to climate change as well as contributing to current development objective.”
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