Assessment of water yield and evapotranspiration over 1985 to 2010 in the Gomti River basin in India using the SWAT model

Soil and Water Assessment Tool (SWAT) was used to assess the water yield and evapotranspiration for the Gomti River basin, India for over a period of 25 years (1985-2010). Streamflow calibration and validation of results showed satisfactory performance (NSE: 0.68-0.51; RSR: 0.56-0.68; vertical bar PBIAS vertical bar: 2.5-24.3) of the model. The water yield was higher in the midstream sub-basins compared to upstream and downstream sub-basins whereas evapotranspiration per unit area decreased from upstream to the downstream. Both evapotranspiration and water yield at upstream and midstream sub-basins increased from 1985 to 2010, whereas water yield at downstream decreased from 1985 to 2010. We found that the spatial and temporal patterns of evapotranspiration and water yield were closely linked to climatic conditions and irrigation in the basin. The long-term trends in water yield point to a drying tendency of downstream sub-basin covering the districts of Jaunpur and Varanasi.