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Chapter One
Introduction
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Learning Objectives
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•
•
•
•
At the end of this chapter the students will be
able to:
Define Irrigation, irrigation engineering and
related terms,
Explain the phases of irrigation,
List the advantage and disadvantage of Irrigation.
Describe the necessity of irrigation
List and explain the scope of irrigation,
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Learning Objectives
• Explain the factors to be considered in the
deciding the need for irrigation.
• List and discuss about the different types of
irrigation schemes.
• Discuss the historical development and current
status of irrigation in the world.
• Discuss the history and status or irrigation
development in Ethiopia.
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Contents of the chapter
1. Introduction
1.
2.
3.
4.
5.
6.
7.
8.
Definition
Phases of irrigation engineering
Necessity of Irrigation
Advantage of Irrigation
Disadvantage and Ill-effects of Irrigation
Requirements for Successful Irrigation
Scope of Irrigation
Economics of Irrigation
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Contents of the chapter
2. Types of Irrigation Systems
3. Irrigation History and Development
4. Agriculture and Irrigation Development in
Ethiopia
4.1 Agriculture
4.2 Irrigation
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1.1 Definition of Irrigation
• Irrigation may be defined as
science of artificial application of water to the land,
in accordance with the crop requirements
throughout the crop period
for full-fledged nourishment of the crops
● Irrigation Engineering is an engineering which is concerned with
the design, layout and construction of irrigation structures and
systems.
● mainly concerned with the design, lay out and construction of
head works, canals, canal structures, cross drainage works and
canal falls.
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1.1 Definition of Irrigation
• According to an eminent engineer N.D. Gulhati,
Irrigation is the "science of survival" for the ever
increasing mankind.
• It includes the following activities/works:
training and tapping of sources of water,
storing of water,
conveying that water efficiently to the fields (It
includes drainage of surplus water also), and
using that supply of water economically for the
bumper crop production. '
,
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1.1 Definition of Irrigation
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1.2 Phases of Irrigation
• Irrigation can be divided in two main phases,
namely:
(a) Engineering phase
(b) Agricultural phase
• Engineering phase: includes
training and tapping of sources of water,
storing of water,
conveying that water efficiently to the fields
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1.2 Phases of Irrigation
In Engineering phase the following are
performed
(a) Assessment of the availability of suitable source of
water
(b) Deciding mode of utilization
(c) Modifying flow conditions
(d) Conveying that water efficiently to the fields
(e) Application of water to the fields
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1.2 Phases of Irrigation
• In Agricultural phase the following are
performed
(a) evolving suitable cropping pattern,
(b) study of soil moisture availability,
(c) determination of crop water
requirement.
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1.2 Phases of Irrigation
d) deciding depths of water with respect to
time over the crop period,
e) arranging equitable distribution of
water.
f) examination of quality of water
g) application of other inputs like high
yielding varieties of seeds, chemical
fertilizers and pesticides etc.
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1.3 Necessity of Irrigation
•
•
•
•
•
•
•
•
Inadequate rain fall
Uneven distribution of rainfall
Increasing the yield of crops
Growing a number of crops
Growing perennial crops
Growing superior crops
Insurance against drought
Controlled water supply
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Cont…
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Cont…
• Application of water to the soil by irrigation
methods serves the following purposes.
It adds water to the soil to supply the moisture
essential for the plant growth.
It saves the crops from drying during short duration
of droughts.
It cools the soil and the atmosphere,
It washes out or dilutes salts in the soil.
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1.4. Advantage of Irrigation
•
•
•
•
•
•
•
•
•
Increase in Food Production
Optimum Benefits
General prosperity
Elimination of Mixed Cropping
Generation of Hydro-electric power
Domestic water supply
Facilities for communications
Inland Navigation
Afforestation
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1.5. Disadvantage of Irrigation
•
•
•
•
Raising water table
Formation of marshy and water logged land
Cause colder and damper condition
Loss of valuable land due to storage of water in
the reservoir
• May contribute to water pollution
• May cause increase in salinity of soil
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1.6 Requirements for Successful Irrigation
•
•
•
•
•
•
Land capability
Adequate Water Supply
Adequate Labor
Climate
Adequate Capital
Favorable policy
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1.8 Scope of Irrigation
• Irrigation engineering is not confined only to the
application of water to the land for raising crops.
• It includes all aspects and problems extending
from the watershed to the agricultural fields.
• It embraces almost all the aspects of water
resources and hydraulic engineering and the
multipurpose river valley projects
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1.8 Scope of Irrigation Engineering
• It embraces the following fields
 Hydrology, hydraulics, Open channel
 River engineering,
 The design and construction of dams, weirs, canals and various
other hydraulic and irrigation structures,
 Drainage, soil reclamation, irrigation practices and water-soil-crop
relationships.
 Soil mechanics, RC, Foundation Eng
 Flood control, hydropower, inland navigation
 Economics, Management, Sociology
 Road construction
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1.8 Scope of Irrigation
• The various aspects of irrigation engineering can
be divided into the following sub-heads.
A. Water Resources and Hydrology aspect
B. Engineering aspect
C. Agricultural aspect
D. Management aspect
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A. Water Resources and Hydrology Aspect
• The basic knowledge of water resources and hydraulic engineering and
hydrology is essential for an engineer.
• While designing and planning various irrigation structures the engineer
requires the following information:
 The quantity of water that will be available at a reservoir site for storage
 The max & min discharge at a river site
 The reservoir capacity that would be required to assure adequate water
 The effects which are likely to occur on the discharge, water levels and
characteristics of the river after the construction of various irrigation
structures.
 The quantity of ground water which can be economically exploited for
various uses,
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B. Engineering Aspect
• The engineering aspect of irrigation engineering involves
 development of a source of water for irrigation
 construction of various irrigation structures for the storage,
diversion, conveyance and application of water.
• It is a vast field and can be subdivided into the following:
(i) Dams and water power engineering
(ii) Diversion and Distribution structures.
(iii) Minor irrigation schemes.
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C. Agricultural Aspect
• The agricultural aspect involves the
following
(i) Irrigation Practice
(ii) Study of agricultural characteristics
(iii) Command Area Development (CAD)
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D. Management Aspect
• It deals with the successful implementation and efficient
management of engineering and agricultural works
• Some points to be considered in the efficient management of the
project are as follows
 There should be most economic use of available water
 The cultivation should be carried out in the most scientific manner
 The distribution of water among various cultivators should be managed
properly.
 Reliable and efficient service should be provided to the cultivators
 Proper arrangement for the measurement of water
 In order to increase the efficiency of irrigation, the small land holdings of the
small farmers should be consolidated to form large holdings.
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2. Types of Irrigation Systems
• Irrigation schemes may be classified in different
ways as indicated below :
– Classification Based on the Level of the
Available Water
– Classification Based on the Duration of
Irrigation
– Classification Based on Size of Command Area
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A/ Classification Based on the Level of the
Available Water
• Based on the level of the available water, the irrigation schemes can be
classified into the following two types
1. Flow Irrigation system
2. Lift Irrigation system
Flow Irrigation system:
 irrigation water is available at a high level
 water is conveyed to the irrigated fields by gravity flow (open channel
flow).
• The flow irrigation systems can be further classified on the basis of the
source of water from which the flow irrigation canals take off.
(a) Direct Irrigation system (b) Storage Irrigation system
(c) Combined Direct and Storage Irrigation system.
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A/ Classification Based on the Level of the Available Water
A/ Direct Irrigation System:
• water is directly diverted to the canal without
creating a storage reservoir.
• A low diversion weir (or a barrage) is usually
constructed across the river for raising the water
level so that it can flow into the canals.
• Used for the perennial rivers which have
adequate flow throughout the year.
• also called the diversion scheme.
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Direct Irrigation System
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Direct Irrigation System
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Direct Irrigation System
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Direct Irrigation System
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Direct Irrigation System
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Direct Irrigation System
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Direct Irrigation System
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(b) Storage Irrigation System
Storage Irrigation System:
● a dam is constructed across the river for creating a large storage
reservoir .
● canals take off from the reservoir.
● comparatively larger in size and involve much more expenditure.
● used when the river is non-perennial and
does not have
adequate flow throughout the year.
● Tank irrigation system is a small storage irrigation scheme in which
a small dam (or a bund) is constructed across a small stream to
create a small pond .
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Storage Irrigation System
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Storage Irrigation System
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Storage Irrigation System
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(c) Combined Direct and Storage Irrigation system
 used for the non-perennial rivers.
● a storage reservoir is created by constructing a dam at a suitable
site.
● canals do not take off from the reservoir. Water is released from
the reservoir into the river downstream of the dam.
● A diversion weir (or a barrage) is constructed on the river at
a suitable place on the down-stream of the dam to divert water
into the canals .
● The weir in this case is known as the pick up weir
● It is used when a suitable site for the dam does not exist near the
commanded area of the canals.
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(c) Combined Direct and Storage Irrigation system
Irrigation Engineering
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(c) Combined Direct and Storage Irrigation system
Irrigation Engineering
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2. Lift Irrigation System:
● used when the water is available at a level lower than the ground
surface/point of use.
● water is lifted up by pumps and other mechanical means and
supplied to the agricultural fields.
● Irrigation from wells is the most common type of lift irrigation
system. Sometimes, water is pumped out directly from the river or
canals for lift irrigation system.
● costlier than direct irrigation systems and are used only when
adequate quantity of water is not available at a high level.
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2. Lift Irrigation System:
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2. Lift Irrigation System:
Irrigation Engineering
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B/ Classification Based on the Duration of Irrigation
• On the basis of duration of irrigation, the
irrigation systems may be classified into the
following two types .
 Perennial Irrigation System
 Non-Perennial Irrigation System
Irrigation Engineering
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Classification Based on the Duration of Irrigation
• Perennial Irrigation System:
 irrigation water is available throughout the year.
 Water is supplied to the fields as per the requirements of the
crops at regular intervals throughout the crop period from sowing
to harvesting of the crop.
 All important irrigation systems are perennial irrigation systems.
 It is the most commonly used irrigation system.
 The water for the perennial irrigation system may are obtained
from a flow irrigation system or a lift irrigation system or a
combination of both these systems.
Irrigation Engineering
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Classification Based on the Duration of Irrigation
• Non-Perennial Irrigation system:
a large quantity of water flowing in a river during floods is
used to flood (or inundate) the land to be cultivated.
The flood water causes saturation of the soil in the fields.
The excess water may drain off before cultivation is done.
The moisture stored in the soil is generally sufficient to
bring the crops to maturity
Irrigation Engineering
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Classification Based on the Duration of Irrigation
Irrigation Engineering
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Classification Based on the Duration of Irrigation
Irrigation Engineering
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Classification Based on Size of Command Area
• Based on the Cultivable/culturable commanded
area (CCA), irrigation system are, classified into
four types:
1. Major projects / Large scale irrigation
2. Medium projects/ Medium scale irrigation
3. Minor projects/ Small scale irrigation
4. Micro Irrigation
Irrigation Engineering
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An Historical Perspective
• Irrigation is an old art as old as civilization
•
•
•
•
•
Nile River Basin (Egypt) - 6000 B.C.
Tigris-Euphrates River Basin (Iraq, Iran, Syria) - 6000 B.C.
Yellow River Basin (China) - 3000 B.C.
Indus River Basin (India) - 2500 B.C.
Maya and Inca civilizations (Mexico, South America) - 500
B.C.
• Western U. S. - 1800’s
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Agriculture and Irrigation Development in Ethiopia
The Ethiopian economy is dominated by
smallholder subsistence agriculture
It accounts for 46 per cent of GDP and 85 per
cent of employment.
It is entirely sector depends on rainfall
10 million hectares of cultivated land
• Only 63,170 ha (0.7 per cent) was under
traditional irrigation in 1998/99.
Irrigation Engineering
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An Historical Perspective




Estimated Irrigation potential vary.
According to WAPCOS, irrigated area =3.73 mill has.
Currently developed= 200000has. Only 4.3%
Ethiopia, faced with rising population pressure, has remained
a food-deficit country since the 1970s.
 In 1999/2000, for example, Ethiopia imported over 800,000
tones of grain in the form of food aid.
• To achieve food self-sufficiency and food security, the current
production shortfalls call for drastic measures to expand
irrigation and improve productivity of rain-fed agriculture.
Irrigation Engineering
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Resources
 Water resource





Twelve river basins
Annual runoff= 122 BMC
Ground water potential= 2.6 BMC
Per capita freshwater= 1,924 m³ (1483.33 m³)
Water tower of East Africa
 Land resource
 total area of about 1.13 million km²
 estimated 55 million ha of arable land
 only 14.8 per cent of the country’s total landmass is being utilized for
crop cultivation constituting just 30 per cent of the arable potential.
Irrigation Engineering
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Irrigation
 Traditional irrigation is very old in the country. They are, however,
small schemes and are simple river diversions.
 Modern irrigation was started at the beginning of 1960's by private
investors.
 In 1991 irrigated land = 197,250 ha
 64000 ha under SSIS
 112,105 ha under MSIS and LSIS
 In 1998 increased from 176,105 ha to 197,250 ha
• On a per capita basis, Ethiopia has developed irrigation over an area
of a mere 0.3 ha per 100 people, vis-à-vis its potential of about 4.0
ha per 100 people.
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Categories of irrigation schemes
There are four categories of irrigation schemes
countrywide
They include :
traditional small-scale schemes
modern communal schemes,
modern private schemes
public schemes
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Categories of Irrigation schemes
Traditional small-scale schemes /Small-scale:
traditional communities
• Built traditionally by farmers at their own initiative,
with government technical and material support.
• They manage them in their own users’ associations or
committees,
• irrigating areas of 50 to 100 ha, the average ranging
from 70 to 90 ha.
• A total of 1,309 such schemes existed in 1992, covering
an estimated 60,000 ha.
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Categories of Irrigation schemes
 Modern communal schemes /Small- to medium-scale: modern
communal schemes
• Built by Government agencies with farmer participation
• Areas extending from 20 to 200 ha.
• Were developed after the catastrophic drought of 1973 as a means to
improve food security and peasant livelihoods.
• There are 288 modern communal schemes in Ethiopia that are capable of
irrigating a total of approximately 30,000 ha
• They are generally based on run-of-river diversion of streams and rivers,
and may also involve micro-dams for storage.
• Beneficiary farmers usually operate and maintain them through users’
associations
Irrigation Engineering
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Categories of Irrigation schemes
 Modern private schemes/Medium- to large-scale: private
enterprise
 Owned and operated by private investors
• Private estates pioneered the development of medium and large-scale
irrigation projects in the Upper Awash region during the 1950s and
1960s.
• They were unexpectedly nationalized in the mid-1970s.
• During the 1990s some private schemes, mostly in the form of limited
companies, re-emerged with the adoption of market-based economic
policy but have expanded relatively slowly.
• Currently 18 modern private irrigation projects are operating in some
form over a total area of 6,000 ha.
Irrigation Engineering
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Categories of Irrigation schemes
 Public schemes /Large-scale: public schemes
 owned and operated by public enterprises, as state farms.
 relatively recent, having started late in the 1970s.
 Gode West, Omo Ratti, and Alwero-Abobo, began late in the 1980s and
early in the 1990s, but have not yet been completed.
 Most large-scale schemes, excepting the Finchaa Sugar Estate
(currently operating successfully), have been suspended
 Area over 3,000 ha
 The recently issued water management policy has, however,
committed the Federal Government to small- and large-scale project
development in the new millennium
Irrigation Engineering
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Irrigation Development Program
 Ethiopia was irrigating fewer than 200,000 hectares (ha) of farmland
at the turn of last millennium, although a total of 3.7 million ha had
been classified as potentially irrigable.
 This gross underdevelopment of capacity to grow food and industrial
crops has spurred the Irrigation Development Program (IDP) to put
an additional 273,829 ha under irrigation, an increase of 135 per
cent of currently irrigated farmlands, within its 15-year plan period
of 2002–2016.
 The central role of irrigated agriculture within the context of poverty
reduction is well understood in Ethiopia
• Irrigated agriculture is important in stimulating sustainable
economic growth and rural employment, and it is the cornerstone
for food security and poverty
reduction.
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Irrigation Engineering
Irrigation Development Program
Accordingly, the IDP attempts to target the
following specific objectives so as to achieve
the overall goal of sustainable development.
• Increase food production, leading to
improvements in nutritional status and
economic well-being among the people.
• Increase production of agricultural raw
materials for industries and export.
•
Develop
capacities
for
planning,
implementing,
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Irrigation Development Program
• Exploit land and water resources to enhance
sustainability of agriculture and rural
livelihoods.
• Reduce dependence on rain-fed water sources
for agriculture and vulnerability to erratic
rainfall patterns.
• Expand rural employment opportunities
through increased agricultural activity.
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Irrigation Development Program
• IDP Components
• During the short-term, the large-scale projects of Omo Ratti (for 8,700 ha
of new coverage) and most (72 per cent) of the Koga project (for 4,344 ha)
will be implemented.
• During the medium-term, 4 large-scale and 2 medium-scale project will be
implemented, for a combined area of 34,236 ha; they include
Alwero/Abobo (for 10,400 ha), Gode West and a small part of Gode South
(9,000 ha), Koga (1,656 ha), Megech (10,018 ha), Nagi Beach (2,070 ha),
and Azena/Ayo (1,092 ha).
• During the long-term, 11 projects will be implemented that comprise 10
large-scale and 1 medium-scale scheme and cover a new area of 71,963 ha;
with an additional 21,518 ha of large-scale schemes
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Irrigation Development Program
• IDP Planning
• The IDP is an effort to promote sustainable agricultural development.
• In this context, it determined the new areas of irrigated cropland that
would be required to satisfy the demand for agricultural products from
the projected population at the end of each of the three 5-year periods of
program (i.e., 2006, 2011, and 2016).
• Population projections by the Central Statistical Authority were used in
estimating national demand for cereals, seed cotton, and sugar crops for
three planning horizons.
• Table 1.5 Projected demand for cereals, cotton, and sugar and estimates
of required irrigated area over the planning horizon (2001–2016)
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Irrigation Development Program
Incremental Demand (Million )
Cereals
Seed Cotton
Sugar
Total
Irrigated
Year
Populatio
Area
n
Required
(Million)
Tons
Ha
Tons
Ha
Tons
Ha
(Million Ha)
2001
65.26
2.59
0.992
0.26
0.116
0
0
1.108
2006
74.83
3.62
1.117
0.49
0.194
0.210
0.019
1.330
2011
85.50
4.90
1.213
0.85
0.298
0.620
0.052
1.563
2016
96.34
6.25
1.250
1.41
0.441
1.420
0.118
1.809
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Irrigation Development Program
• IDP Target setting
• The IDP has set the following average annual growth-rate targets for
the development of irrigated area:
(a) 4.5 per cent during the short-term period;
(b) 5.5 per cent during the medium-term; and
(c) 6.5 per cent during the long-term.
●Increases in agricultural production resulting from the new irrigation
projects are expected to reduce the national
● cereals deficit by 11 per cent and
● the deficits in seed cotton and sugar crops by 24 per cent each.
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Table 1.6 Targets for the Irrigation Development Program (2002–2016)
Large- and
Small-scale
medium-scale
Description
schemes
schemes
Short-term 1st 5 years: (2002-2006):
40,319
13,044
53,363
Medium-term 2nd 5 years: (2007- 2012):
40,348
39,701
80,049
Long-term 3rd 5 years: (2012-2016):
46,471
94,729
141,200
2016:
127,138
147,474
274,612
Currently developed (approximate):
98,625
98,625
197,250
Grand total irrigated area by 2016:
225,763
246,099
471,862
Total area
Total area to be developed during 2002-
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Summary of major constraints
• Absence of a coherent development policy, strategy, and
program, until very recently.
• Low institutional capacity and effectiveness.
• Shortage of financial resources coupled with immense
investment requirements, particularly in the case of large-scale
projects.
• Lack of coordination among the various implementing
institutions:
Federal
Government,
Regional
(State)
Governments, NGOs, donors, and others involved.
• Lack of appropriate technology at the level of local resources.
Irrigation Engineering
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Summary of major constraints
• Low level of infrastructural development that would allow easy
access to inputs and outputs.
• Absence of involvement of the stakeholders in the
development process.
• Inadequate technical capacities.
• Lack of data and information required for efficient sector
planning and management.
• Insufficient public-private partnerships.
• Low water use efficiencies in all water consuming sectors.
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List of Federal Government LS & MS irrigation projects
•
•
•
•
•
•
•
•
•
•
•
•
Alwero Abobo 1
Omo Ratti
Gode 2
Koga3
Dabus
Ribb
NE Tana
Megech
Gilgel Abbay-5
Upper Guder
NW Tana
Gumara
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List of Federal Government LS & MS irrigation projects
•
•
•
•
•
•
•
•
•
•
•
•
•
SW Tana
Tis Abbay Pump.
Tis 3-5
Azena/Ayo
Study/Part Imp:
Arjo-Didessa
Negesso
Dabena
Angar
Nekemte
Humera
BaroRB
Upper Beles
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