Assessment of spatio-temporal variation of water balance components by simulating the hydrological processes of a large complex watershed

This study explains the application of the semi-distributed hydrological model, mainly in the semi-arid regions of India. It is quite complicated to do the multi-site calibration for a complex river basin, as Middle Tapi basin is surrounded by three major dams. For simulating the stream flows SWAT model was used for the total basin area of 32,927 km2 for a total of 20 years. SWAT-CUP software with the SUFI-2 approach was applied to calibrate, validate, and determine the model performance. Out of 19 parameters, SCS runoff curve number (CN2) came out as the highest sensitive parameter, according to the global sensitivity analysis. The periods of calibration and validation used were 1998–2006 and 2007–2013, respectively. Model performance indicators R2, NSE, and PBIAS for a period of calibration and validation came out to be between very good and satisfactory for Sarangkheda, Gidhade, and Ukai stations. For all three stations on a daily basis, R2 ranges between 0.77 and 0.85, NSE between 0.76 and 0.84, and PBIAS (%) between − 19.9 and 5.7 for the calibration period; and for the validation period, R2 ranges between 0.76 and 0.79, NSE between 0.7 and 0.77 and PBIAS (%) between − 24.7 and 13.5. Using DEM, the delineation of the watershed was completed and divided into 65 sub-watersheds depending upon the area contributing to it and the direction of the flow. The highest groundwater and surface discharge were detected in subbasins 9 and 25. The highest evapotranspiration was seen in subbasins 64 and 11. The wettest year was 2006, while the driest was 2000. Most of the precipitation, surface runoff, and evapotranspiration occurred from July to September.