SPATIAL MAPPING OF AGRICULTURAL WATER PRODUCTIVITY USING THE SWAT MODEL IN UPPER BHIMA CATCHMENT, INDIA

The Upper Bhima River Basin is facing both episodic and chronic water shortages due to intensive irrigation development. The main objective of this study was to characterize the hydrologic processes of the Upper Bhima River Basin and assess crop water productivity using the distributed hydrologic model, SWAT. Rainfall within the basin varies from 450 to 5000 mm in a period of 34 months. The basin has an average rainfall of 711 mm (32 400 Mm(3) (million cubic metres)) in a normal year, of which 12.8% (4150 Mm(3)) and 21% (6800 Mm(3)) are captured by the reservoirs and groundwater reserves, respectively, 7% (2260 Mm(3)) exported as runoff out of the basin and the rest (63%) used in evapotranspiration. Agricultural water productivity for sugarcane, sorghum and millet were estimated as 2.90, 0.51 and 0.30 kg m-3, respectively, which were significantly lower than the potential and global maximum in the basin and warrant further improvement. Various scenarios involving different cropping patterns were tested with the goal of increasing economic water productivity values in the Ujjani Irrigation Scheme. Analysis suggests that maximization of the area by provision of supplemental irrigation to rainfed areas as well as better on-farm water management practices can provide opportunities for improving water productivity. Copyright (C) 2011 John Wiley & Sons, Ltd.