Priyamitra Munoth

The present study developed an integrated hydrologic model for sustainable utilisation and water management in two complex watersheds with varying physioclimatic features and reservoirs. The soil and water assessment tool (SWAT) is used for predicting integrated inflows into the Hatnur reservoir from the Burhanpur and Purna watersheds of the Upper Tapi River basin, while outflows are simulated using a rule curve. The influence of watershed complexities on hydrological model parameters and the watershed processes are investigated using extensive multisite and multivariable calibration (1998–2007) and validation (2008–2013) approaches, including sensitivity and uncertainty analyses. The sensitive parameters are related to curve number (CN), groundwater, slope, and main channel characteristics. The annual streamflow (m3/km2/mm of rainfall) in the Burhanpur watershed is 568.7, which is 4.2 times higher than the Purna watershed's streamflow of 136.2. The hypsometric analysis, areal rainfall, and flow duration curves revealed a substantially different streamflow pattern and a larger coefficient of variation in the spatial distribution of water balance components over sub-watersheds in the Burhanpur watershed compared to the Purna watershed due to diverse topographic features. The developed model would be useful for planning controlled releases from the terminal reservoir to mitigate hazards in the downstream reaches of the Tapi River basin.

Land use land cover (LULC) changes can result in shortage of water, flood risk and soil erosion and thus contribute to the deterioration of living conditions. Understanding the impacts of LULC changes on water resources is therefore an important research issue for watershed management. Therefore, this paper discusses the impacts of LULC changes on surface runoff and sediment yield of Upper Tapi River Sub-basin, India using Soil and water assessment Tool (SWAT). The land use dynamics of the sub-basin was assessed through the analysis of four land use maps corresponding to year 1975, 1990, 2000, and 2016. It is found that from the year 1975 to 2016 agricultural area is increased by 18% whereas forest land and rangeland are decreased by 7% and 10% respectively. This land use change may lead to land degradation and ecological damages in the study area. These LULC maps were used to calibrate four separate SWAT models with the corresponding climate data from 1979 to 2013. These models performance are evaluated based on R², ENS and PBIAS values which indicate very good agreement between observed and simulated discharge. The impacts of LULC changes were assessed by four different scenarios in which climate data (1979-2013), Soil map and slope map were kept same, and only the land use maps were changed. The results of this study showed that LULC changes have resulted in corresponding increase in surface runoff, water yield, and sediment yield. The surface runoff has increased about 36% and water yield has increased about 22%. Similarly, sediment yield is also increased around 22% from the scenario S₁ to S₄. The outputs of this study could be used for soil and water conservation and river health protection in the Upper Tapi River Sub Basin.