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1.., Introduction, About This Chapter, After reading this chapter students can understand., Irrigation Engineering, Type of Irrigation, Advantages of Irrigation, Methods of Irrigation, 1.1 DEFINITION OF IRRIGATION, Irrigation may be defined as the scientific artificial application of water to the agricultural land to supply, necessary moisture to the crops as and when required for its healthy growth., The water is supplied throughout the crop-period for full-fledged nourishment of the crops. In the, absence of required quantity of moisture in the soil, the plants and crops cannot grow., It is a science of the planning and designing an efficient, low cost, economical irrigation system tailored, to fit the natural conditions., 1.2 IRRIGATION ENGINEERING, Irrigation engineering is a branch of civil engineering which deals with the investigation, planning,, construction, management and maintenance of all structures connected with irrigation., The structures comprise of:, (1) Dams, diversion weirs, wells, tubewells., (2) Canals and canal masonry works etc., 1.3 NECESSITY OF IRRIGATION IN INDIA, India is basically an agricultural country and all its resources depend on the agricultural output. India, being a tropical country, there is a vast diversity of climate, topography and vegetation., The amount and frequency of rainfall varies from place-to-place., Water is evidently the most vital element in the plant life. Crops cannot therefore be raised successfully, over the entire land. The total rainfall in a particular area may be either insufficient or ill-timed., Crops require certain quantity of water after certain fixed interval throughout its period of growth., If rain water falling directly on land on which the crop stands can satisfy both these requirements,, irrigation water will not be required for raising this crop., But it rarely happens, and in order to save this area from the complete wishes of nature and to ensure, full growth of crops, it is necessary that adequate irrigation facilities are ensured., Indian Government is spending lot of amount to ensure irrigation facilities for the maximum cultivable, area., Thus, the necessity of irrigation can be summarised in the following four points., (1) Less rainfall., (2) Non-uniform rainfall or ill-timed rainfall., (3) Cultivation of cash crops with additional supply of water., (4) Controlled water supply., (1.1), 1

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Irrigation Engineering, 1.2, 1.4 ADVANTAGES OR BENEFITS OF IRRIGATION, Introduction, Benefits of irrigation are of two types direct and indirect., 1.4.1 Direct Benefits, Some of the direct benefits of irrigation are as under:, (1) Increase in food production : Irrigation helps in increasing the yield of the crops. Two or more, crops can be taken on the same land. Early growing and better yielding hybrid cereals can be sown., Fish production can be developed in the irrigation tanks., (2) Protection from famine : Irrigation protects people from the occurrence of famines when rainfall, in any year is much less than normal. During the construction of irrigation works, employment is, created to the people and thus they get some relief against famine., (3) Cultivation of cash crops Irrigation makes it possible to grow cash crops such as sugarcane,, banana, tobacco, cotton etc. More money will be available with the farmers which raises their, standard of living., (4) Flood control : Irrigation reservoirs detain flood water sometime and hence reduces possibility of, flood damages., (5) Generation of hydro-electric power : Hydro-electric power can be generated from falls on some, canals or by water stored in a storage reservoir. This cheap power will serve many agricultural,, domestic and industrial purposes., (6) Domestic and industrial water-supply : Irrigation helps in augmenting the town-water supply, which can be used for domestic and industrial purposes., (7) Inland navigation : Some large canals can serve the dual purpose of irrigation and navigation., 1.4.2 Indirect Benefits, (1) Increase in revenue to the government : Government spends lot of money on the construction of, irrigation projects and makes irrigation water available to the cultivator. Government takes, irrigation cess for this facility and thus it is a paying concern to it., (2) Increase in communication : Project approach roads, canal roads ferry services, telegraph and, telephone lines increase the communication facilities., (3) Canal plantation : Trees are generally grown along the banks of the canals, distributeries,, watercourses etc. This increases the timber wealth of the country and also prevents the erosion of, soil., 1.5 DISADVANTAGES OF IRRIGATION (III Effects of Irrigation), (1) Water logging : Water logging renders the soil infertile and useless for cultivation., (2) Salt efflorescence due to water logging. It damages the soil., (3), Breeding of mosquitoes., Damp climate The climate becomes cold and damp due to intense irrigation of an area. This, (4), unhealthy climate causing malaria disease., (5) Excessive humidity : Excess and intense irrigation may result in increasing the humidity of the area., (6) Ecological imbalance., 1.6 TYPES OF IRRIGATION OR METHODS OF IRRIGATION, The various types of irrigation can be broadly classified as follows:, Irrigation, Flow irrigation, Lift irrigation (sub-soil water irrigation), Perennial, Inundation, irrigation, irrigation, Direct irrigation, or River canal irrigation, Storage irrigation or, valley irrigation, 2

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Irrigation Engineering, 1.3, Introduction, 1.6.1 Flow Irrigation, In flow irrigation, the irrigation water flows to the land by gravity. It may be:, Perennial irrigation or, (), (ii) Inundation or flood irrigation., (i) Perennial Irrigation : In this system, some storage head works such as dams, storage weirs or, barrages are constructed to store the water. The water required for irrigation is supplied according, to the crop requirements throughout the crop period., (ii) Inundation Irrigation : It is also called as river canal irrigation. In this type, there is no irrigation, work across river to control the level of water in the river. The canal is seasonal as the water is, available in it for a particular season during floods in a year. It is classified as follows :, (a) Direct Irrigation or Rivers, Canal Irrigation :, In direct irrigation, water is taken directly from river by means of main canal. For such system, a low, diversion weir, bandhara or barrage is constructed across river, to raise the level of water in river, and thus divert the water to the canal., Generally, direct irrigation schemes are of small magnitude, and are practised where the river is, perennial., Diversion weir, Right main canal, CDW, Left main canal, River, CDW, Drain, Drain, T.E., J.C., Tributary, C.D.W. = Cross drainage works, T.C. = Tail cluster, T.E. = Tail escape, Fig. 1.1: Direct irrigation system, (b) Storage Irrigation :, In case of storage irrigation, a solid barrier such as dam or a storage weir is constructed across the, river and water of river flowing during rainy season is stored in the reservoir at the back of such, barrier., Storage irrigation scheme is comparatively bigger in magnitude and involves construction of head, works. There may be one or two canals taking-off from the reservoir., In India, most of the irrigation schemes fall under this category. This system is economical and, reliable. If a project is located in the valley of a river, it is called valley irrigation project and when it, is located in the delta of a river, it is called delta irrigation project., 3, Marginal bund, River, Marginal bund

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Irrigation Engineering, 1,4, Introduction, River, Reservdir, DAM, Drain, Drain, ATH.R., C.R Distributary, C.R., TE., Tributary, H.R., T.C., .E., T.E, Tributary, H.R. = Head regulator, C.R. = Cross regulator, T.E. = Tail escape, T.C. = Tail clusture, S = Superpassage, T= Tributary, A = Aqueduct, Fig. 1.2 : Storage Irrigation Scheme, 1.6.2 Lift Irrigation, In this system, the source of water is the underground water., The water can be lifted by sinking wells and tube-wells by mechanical means., It can be lifted from rivers or lakes for irrigation purpose. This water is then supplied to the nearby land., Well irrigation is more widely practised in deltaic areas but it is also spread in non-deltaic areas. This is, costly, uneconomical and reliable., 1.6.3 Comparison between Perennial Irrigation System, and Inundation Irrigation system, Perennial irrigation system, Inundation irrigation system, 1. In this system water can supplied as per the 1. No control over water as per requirement., required., 2. In this system dams, storage weirs or barrages 2. No storage of water is possible., are constructed to store the water., 3. This system is useful throughout the crop period. 3. This system is seasonal as the water is available, 4. Water is obtained by flow irrigation system or a, lift irrigation system., in it for a particular reason during foods., 4. Water is obtained by conveying it through, cannal., 4, Right main canal, TH.R., Branch canal, River, C.R., CF, Left main canal, Distributary

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Irrigation Engineering, 1.5, Introduction, 1.7 CLASSIFICATION OF IRRIGATION WORKS, The irrigation works can also be classified as follows :, 1.7.1 Purpose Wise Classification of Reservoirs, A reservoir may be planned for the various purposes such as irrigation, water-supply, flood control,, recreation etc., (a) Single Purpose Project : A project planned for one or single purpose is called as single purpose, project., Examples of this type are Koyna Project for hydro power, Gangapur Project for irrigation, Hatnur, Project for irigation., (b) Multipurpose Project : A project planned for more than one purpose is called a multipurpose, project., Examples of this type are Bhakra Nangal Project for irrigation and hydro-power generation, Damodar, Valley Corporation for irrigation, flood control and power generation, Pench project for irrigation and, power generation, Jayakwadi project for irrigation and power., 1.7.2 Administrative Classification, The irrigation works are classified for the purpose of administration as (i) Major projects, (ii) Medium, projects, (iii) Minor projects., Major projects : Major projects are those which have irrigation potential of more than 10,000 hectares, and which cost 50 millions and above., Medium projects : Medium projects are those which have irrigation potential between 2000 to 10,000, hectares and cost between 25 million to 50 million., Both major and medium projects are financed by the Government from five year development plans., For these projects, the benefit cost ratio should be 1.5., Net benefit or gain accruing from the project, Cost of the project, Benefit Cost Ratio =, Minor projects : Minor projects are those which irrigate less than 2000 ha. and cost less than 2.5, million. These include small tanks, percolation tanks, bandharas, wells and tube wells., The yard stick of benefit cost ratio is not applied to minor tanks. These works are financed by private, finances aided by the Government in the form of loans and grants and also by State Government itself., 1.8 IMPORTANT RIVERS IN INDIA, In India, there are 12 major river basins with drainage area exceeding 20,000 sq. km., (4) Krishna, (8) Tapi, (2) Ganga - Brahmputra, (6) Brahmani - Baitarni, (10) Narmada, (3) Godavari, (7) Pennar, (1) Indus, 5) Mahanadi, (9) Cauvery, (11) Mahi, (12) Sabarmati., 1.9 IMPORTANT DAMS IN INDIA, (1) Bhakra Dam (River Satlaj, H.P.)., (3) Nagarjun Sagar Dam (River Krishna, A.P.)., (5) Rihand Dam (River Rihand, U.P.)., (7) Ukai Dam (River Tapi, Gujarat)., (9) Ujjani Dam (River Bhima, M.S.)., (2) Koyna Dam (River Koyana, M.S.)., (4) Gandhi Sagar Dam (River Chambal, M.P.)., (6) Hirakud Dam (River Kirakud, Orissa)., (8) Tehri Dam (River Bhagirathi, U.P)., (10) Tungbhadra Dam (River Tungbhadra, Karnataka).., 1.10 IMPORTANT RIVERS IN MAHARASHTRA, (1) Narmada, (2) Tapi, (3) Girna, (4) Purna, (5) Godavari, (9) Bhima, (14) Koyna, (19) Pench, (24) Bogavati, (10) Vaitarna, (15) Panchganga, (20) Indravati, (25) Darna, (8) Ghod, (13) Savitri, (6) Pravara, (11) Tansa, (16) Mnjra, (21) Krishna, (26) Nira., (7) Mula, (12) Ulhas, (17) Penganga (18) Wardha, (22) Mutha, (23) Bindusura