Theme 2-20-Optimum lining of distribution network for effective reduction in ground water withdrawal in a distributary canal command

Abstract

Water is the crucial input for crop production. Canal irrigation is always preferred by the farmers over the other conventional methods due to lower cost of irrigation and ease in its application. But because of limited water availability at the reservoir, the canal water alone may not be sufficient to irrigate the whole command area. On the other hand the lower conveyance efficiency of the distribution system results in further reduction in the actual availability of water at farmers' field. Under such conditions the conjunctive use of canal water and water from other sources like ponds or tubewells, has been practiced in all most all the canal irrigated commands. Now due to the alarming decline of water table in many commands the emphasis is given to reduce the ground water withdrawal and to enhance the conveyance efficiency of the canal distribution systems. The water losses in the form of seepage through bed and banks of irrigation canal network is the prime cause of poor distribution efficiency in a canal command. This not only affects the system performance but also had created waterlogging problem in many canal commands. Therefore, this substantial loss of water through canal seepage clearly indicates that the lining of canal system, to enhance the efficiency and to conserve the land and irrigation water, is badly needed. Keeping it in view the present study was taken up to evaluate twenty four lining alternatives, involving partial or full lining of the distributary, minors and watercourses, in terms of benefit cost ratio, increase in canal water availability at field level and reduction in ground water withdrawal in Bulandshahr distributary command of Upper Ganga canal system. The benefits for an alternative are obtained by using linear programming model. The study reveals that the optimum lining of distribution network will result in more than 50 percent increase in canal water availability at field level. This increased canal water availability intern would result in seven to eight percent reduction in ground water withdrawal in the command. On the basis of different constraints different alternatives of lining have been suggested.