Design of Lift Irrigation Systems
The design of the various components of lift irrigation systems are highly situation specific. Detailed investigation of the site, including river flow characteristics, topography, and climate conditions, mainly rainfall characteristics will enable the development of the system which best suits the requirements and provides maximum possible economy in installation and operating costs. The main structural components on lift irrigation systems are (i) intake structure, (ii) intake pipe, (iii) jack well/pump well,
- (iv) pump house, (v) rising main and accessories, (vi) delivery chamber,
- (vii) distribution chamber, and (viii) on-farm water distribution system. The pumping system equipment comprise of pumps, electric motors/ engines, electrical accessories and fittings, transformer and power connection and protective devices.
Water Lifting from Canals
In canal pumping schemes the capacity of the pumping sets and the periods of pumping have to be fixed after careful consideration of the irrigation requirements of downstream users, including those receiving their supplies from gravity flow and / or are allowed to pump canal flows at specified time periods. The basic requirements of both these categories of users should not be adversely affected by a new pumping scheme. However, in many situations there are ample opportunities to provide adequate supplies for pumping at several points along a canal. They arise due to a change in the cropping system of the command area served by the gravity flow system, in order to combat the problem of excessive rise in ground water table after the introduction of canal irrigation. Canal pumping schemes will help in the effective utilization of canal flows during periods of low demand in the gravity command area. With the present day advances in plant breeding, there is ample scope for selecting crops and their varieties which could be grown successfully during this period. In many regions, the practice of night irrigation is not well established, when surface methods of water application are practiced. Sizable quantities of canal supplies during the night are not effectively utilized. It is desirable to permit pumping during the night to utilize the under-utilized canal flows during the period. There are also situations where the initial reaches of a canal system cannot be brought under gravity flow irrigation due to the unfavorable topography of the surrounding areas. In such cases canal pumping assumes importance as they add to the culturable command area of the canal system. Utilizing canal flows in its upstream reaches results in a major reduction in the total seepage loss of a canal system.
Canal pumping schemes are most economical when the lift command area is close to the canal and the pumping heads are low. In general, lift irrigation results in more efficient use of the canal supplies, as compared to gravity flow systems, as the farmers are more conscious of the cost of pumped water supplied than those obtained from a gravity flow system.