Study on water distribution in Ganges - Kobadak project

Abstract

A field study on water distribution in the Ganges – Kobadak irrigation project during the Aman (Kharif-II) season of 1988 was conducted. The Kushtia main canal, three secondary canals and three tertiar:v canals of each of the selected secondary canals representating the head, middle and tail reaches were Daily data on flow of !-Iater, water adequacy, selected rainfall,evaporation and seepage and percolation and seasonal data on irrigated, area and yield were recorded at each of the nine tertiaries. The existing method of water distribution was evaluated in terms of equity, efficiency and productivity.The technical and institutional constraints in proper implementation of the existing water distribution were identified through field observations and questionnaire survey. The questionnaire survey was conducted among the few selected BWDB officials and farmers of the project area. The prepared 9-day rotational water distribution schedule was found to have some defects and the schedule was not found to be followed. The distribution of water was unequal among different reaches of the system. The average rate of irrigation water delivery per hectare of irrigated land was found to vary widely. from a very low value of 0.27 Ips to a very high value of 4.04 Ips in the selected tertiaries. Deficit irrigation was found in most of the selected tertiary area during the study period. The impact of water distribution on yield was studied. It was found that the yield value was related to some extent to the water distribution pattern of the system. The constraints identified in the implementation of the existing water distribution were inadequate capacity of the canals, poor condition of secondary outlet structures, absence of tertiary outlet structures, poor control of water at different levels, lack of communication between the farmers and the project authority, lack of supervision and lack of water users group. For proper implementation of the rotational water distribution in the project, the capacity of the canal should be increased. Alternate rotation programme which may fit better to the existing canal capacity should also be studied. For controlled water distribution structure should be repaired and maintained properly; tertiary outlet structures should be constructed; water distribution should be regularly monitored and strong water users group should be developed.