Water balance study and performance evaluation of a lift irrigation system

Abstract

Chandpur Irrigation Project (CIP) is one of the successful irrigation projects' of Bangladesh Water Development Board. Although the project has abundant sources of irrigation water, the desired benefit of irrigation has not been achieved, possibly due to absence of improved management and technology, lack of farmer's awareness and inadequate infrastructure facilities. This study has been performed to estimate demand and compare it with the irrigation water supply and to evaluate the system performance in terms of water balance parameters. Water balance study and performance evaluation was performed for irrigation seasons of 1996 and 1998. The inputs (Irrigation water supply and rainfall), outputs (Crop water use and percolation losses) and storage change were calculated for each 10-day period. Irrigation water supply was calculated from the combined discharge and the operating hours as recorded in the logbook. Seepage and percolation from rice field and canal network was considered for this study. The former was taken as 2.5 mm/day and later one was calculated by an assumed value based on global average value of conveyance loss. Crop water requirement was computed using CROPW AT software developed by FAO. Required crop data and climatic data were collected from Department of Agriculture Extension and Bangladesh Meteorological Department respectively. Effective rainfall was calculated by USDA soil conservation service method. The results show that water deficiency occurred in 3 decades out of 10 in 1996 and in 2 decades out of 11. Irrigation water supply situation was more adequate in the irrigation season of 1998 compared to 1996. Seasonal average value of Relative Water Supply was found to be 1.21 in 1996 and 1.08 in 1998. Seasonal Project Efficiency was computed as 62.0 % in 1996 and 64.0 % in 1998. On the other hand Water delivery Performance was computed as 60.9 % in 1996 and 48.0% in 1998. In the irrigation season of 1998 substantial improvement of project performance in terms of water adequacy and efficiency was observed which might be due to the rehabilitation works carried out by the project authority of CIP in 1997.