drainage engineering

1. INTRODUCTION
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2. Content
 Definitions of Irrigation
 Early History of Irrigation Development
 The Need for Irrigation
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3. Definitions:
• Irrigation is the science of artificial application of water to the land,
in accordance with the crop requirements through out the crop
period
 for full-fledged nourishment of crops
 to supplement natural precipitation for crop production
• Irrigation is a process, other than natural precipitation, in which
water flows and spreads over the land to nourish the plant life to
give maximum crop output.
Need for irrigation are as follows :
• Where, Rainfall is not sufficient to supply crop water
needs
• Where rainfall is not uniformly distributed to supplement the crop
requirement
• If there is variable crop water requirement
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4. Early History of Irrigation Development
 For thousands of years, irrigation has contributed
substantially to world food production.
 Historians note that irrigation was one of the first
modifications of the natural environment undertaken by
early civilizations.
 Several millennia ago, irrigation permitted nomadic tribes to
settle in more stable communities with assurance of annual
crop productivity.
 Initial attempts at irrigation were ponding water in basins
enclosed by low earthen dikes. 4

5.  The earliest societies rely on four major river basins for irrigation:
 the Nile in Egypt around 6,000 B.C.E.,
 the Tigris and Euphrates in Mesopotamia about 4,000 B.C.E.,
 the Yellow River in China around 3,000 B.C.E, and
 the Indus in India approximately 2,500 B.C.E.
 Irrigation began to expand in many countries in the nineteenth century
and took on new dimensions in terms of the amounts and methods of
water diversion and management.
 Historians sizing up the twentieth century will almost certainly include
irrigation as one of the century’s characteristics.
 During the first half of the century, irrigated area worldwide rose to
more than 230 million acres.
 The surge continued in the second half of the century with over 800
million acres in 2017.
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6. Table 1.1. Growth in irrigated land and world population since 1900
(adapted from FAOSTAT, 1999; FAO, 1998, 2021).
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7. Table 1.2. Top 10 irrigated countries in the world in 2017 (adapted from
FAO, 2021).
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8.  Many countries such as China, Egypt, India, Indonesia,
Israel, Japan, Korea, Pakistan, and Peru rely on irrigation for
more than half of their domestic food production.
 Large areas of irrigated lands in south-east Asia lie in the
humid equatorial belt.
 These areas have monsoon climates with very large totals of
annual rainfall, but portions of the year are dry.
 In these countries, paddy or flooded rice is the dominate
irrigated crop.
 Countries like China, Korea, Japan, Indonesia, and the
Philippines have long been noted for this type of irrigated
agriculture.
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9.  History of Irrigation in Ethiopia
 In Ethiopia, traditional irrigation was practiced before centuries.
 Moreover, in the highlands of Ethiopia, irrigation practices have
long been in use since ancient times for producing subsistence food
crops.
 Supplementary irrigation has been practiced by smallholder farmers
of Ethiopia for centuries to solve their livelihood challenges.
 Modern irrigation, however, was started in the early 1950’s by the
bilateral agreement between the government of Ethiopia and the
Dutch company jointly known as HVA-Ethiopia sugar cane
plantation.
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10.  Irrigated agriculture was started in Ethiopia in the upper Awash
Valley with the objective of producing industrial crops as
sugarcane, cotton, and horticultural crops on a large-scale basis,
explained in a remarkable emergence of irrigation development
and establishment of agro-industrial centers.
 This was due to taking an advantage of the construction of Koka
dam aimed as a reservoir irrigation water supply, flood control
and hydropower generation.
 During the middle 1970s, windmills and hand pumps were
introduced to lift water from groundwater for drinking water
supply, domestic and gardening purposes (MoA, 2011a).
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11.  The exact date when irrigation was started in Ethiopia
remains uninvestigated regardless of routinely saying
“irrigation was started in Ethiopia during ancient times.
 However, the development of irrigation practices in Ethiopia
must be investigated to seriously know the history of
irrigation emergence and its subsequent developments.
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12. Factors necessitating Irrigation
• Inadequate rainfall
• Non-uniform distribution of rainfall
• Growing of cash crops
• Increasing the yield of the crops per hectare
• Growing a number of crops in a year
• Growing perennial and superior crops
• Insuring against drought
• Growing perennial crops
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13. Cont’d…
Consequences of water shortage
 crop yield reduced
 famines and disasters
So, we need irrigation:
 for a continuous & reliable water supply to crops
 when water supply is not sufficient and timely
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14. Cont’d…
Types of irrigation based on different criteria
 Rainfall availability (Supplementary irrigation / Total
irrigation)
 Size of command area (small, medium and large)
 Application method (surface, sprinkler, drip)
 Source of water (surface, ground water or conjunctive)
 Conveyance method (gravity or pressurized)
 Control system (upstream or downstream)
 Water scheduling (continuous or rotation)
 Payment (area based or volumetric based)
 Location (Supply or demand based)
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15. Cont’d…
Locations Vs Irrigation Need
 Arid and semi-arid regions:
 rainfall does not provide all the water needed
 irrigation can make up the deficiency
 Areas with seasonal rain shortage:
 Irrigation practiced during the dry season
 Humid areas:
 the rainfall is normally adequate
 irrigation is a safe guard against drought
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16. Cont’d…
 The Benefits of irrigation:
 Improve crops quality;
 Stabilize the farm economy;
 Cultivation of superior crops
 Harvest time closely controlled;
 Eliminates mixed cropping;
 Increases the survival of transplanted crops,
 Protects crops from frost/high temperature damage;
 Conjunctive use– hydroelectric power, domestic water supply;
 Communication facility and etc.
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17. Cont’d…
Ill effects (disadvantages) of irrigation:
Occur if scheme is not properly designed & implemented.
 Water logging:
 happen when water table reaches near the root zones
 results colder & damper climate causing disease outbreak (Eg.
Malaria)
Salinity and sodicity
Relatively expensive
Tail end problem,
Social differentiation
Water pollution(seepage of nitrates from fertilizers)
Results in a colder and damper climate(outbreak of diseases such
as malaria)
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18. Cont’d…
Requirements for Successful Irrigation Project
Land Capability:
 Soils that are capable of producing sustained high yields.
Adequate Water Supply :
 adequate to meet the needs of the crops
Adequate Labor :
 Adequate labor and machinery when needed
Climate:
 Suitable to the crops to grow.
Adequate Capital
 Enough initial capital to install, operate and maintain project
Others:
 Effective management of soil and water
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