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Sources of Irrigation Water |
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Determination of amount of water for the field - Gravity water (check dam)- The amount of water is determined by the flow of water from up stream and the total water catchments of the dam. - In case of pumps- the amount of water needed for irrigation (water is planned) by the size of the pump. There fore the size of the pump is influenced by:- 1.8 its total salt content which is expressed in terms of electrical conductivity (E. C.) (In million hrs/cm or ppm) 2. The relative proportion of exchangeable cation of Na+ in comparison with ca++ and Mg ++ ions. This is expressed by sodium absorption ratio (SAR) 3. The contents of bicarbonates and boron, relation tolerance of plants to Borron in irrigation water. Conveyance of water This is may be classified as:- 1) pressure (closed conduct) and - 13 - 2) gravity which includes open channel or closed conduit (partial flow) Open channels- steady uniform flow. When velocity exceeds a certain value, particles are dislodged from sides& bottom of channel so erosion caused by attractive forces. And when velocity fall below certain limit sedimentation ( salutation) is formed. So there is limitation in construction of canals, these are side slops, free boards, should be considered. Canals- can be lened or unlined. Since it is economical to construct lined canals unlined canals are widely used. Advantages of lined canals: 1) Avoiding excessive loss of water due to seepage. 2) To avoid erosion 3) To avoid water logging of adjacent lands due to seepage. 4) To reduce flow resistance. 5) To help in control of weeds aquatic growth. 6) To provide needed side slope stability. |
| Source of Irrigation water The main source of irrigation water are:- 1. Surface water:- is found on the surface of the land. These include spring water, River water, lake water, etc. This can be supplied to the field by wier (check dam) by gravity or by using pump. Check dam /wier/ system is used only when the source of water is from river, or spring water that starts from up stream. - 12 - Where the slop of the source of water is greater than the slop of the field to be irrigated. Pumps are used where the source of water for the field is at down stream (at lower altitude.) Here mostly centrifugal type pumps are used. 2. Ground water:- Where these is shortage of surface water ground water is used for irrigation. This is supplied only by using pumps. | |
