From over to optimal irrigation in paddy production: what determines over-irrigation in Bangladesh?

This paper examines the level of optimal irrigation and the determinants of over-irrigation in paddy production since about three-fourth of freshwater withdrawal is used to irrigate paddy plants in Bangladesh. Cobb–Douglas production function reveals that optimal irrigation is 75 × 10 2 m 3 per acre per season. Results show nearly, 39% of water is over-irrigated. It escalates farmer’s irrigation cost by USD 56 per acre and induces additional depletion 60 × 10 2 million m 3 freshwater with substantial welfare loss USD 70–73 million in south-western Bangladesh. Further analyses reveal that farm characteristics, salinity, and irrigational modes determine over-irrigation in the study area. This study suggests that the alternate wetting and drying (AWD) technique helps farmers to reduce irrigation substantially and to reach the optimal level. Welfare effects of the AWD technique are 89–93% reduction in over-irrigation 68–71% reduction in ancillary cost.