Assessment of spatially explicit annual water-balance model for Sutlej River Basin in eastern Himalayas and Tungabhadra River Basin in peninsular India

In this paper, Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) water yield model, based on the Budyko framework which is relatively simple and requires less data, has been applied in Sutlej River Basin, located in the eastern Himalayas and in Tungabhadra River Basin, located in peninsular India. The effect of extrapolation of the lumped Zhang model to distributed model (InVEST) has also been analyzed. We also determined the most suitable method for calculating reference evapotranspiration among three different methods, i.e., modified Hargreaves, normal Hargreaves and Hamon's equation. It was found that modified Hargreaves method is the most suitable one under limited data conditions although in certain stations in Tungabhadra River Basin, this method is not applicable. We also observed that the InVEST model performed well in the Sutlej River Basin although a certain proportion of the basin is snow covered. The results from the study also show that errors in climate inputs will have significant influence on water yield as compared to other parameters, i.e., seasonality constant (Z) and evapotranspiration coefficient (KC). In the case of the crop dominated Tungabhadra River Basin, both seasonality constant (Z) and evapotranspiration coefficient (KC) have comparatively greater sensitivity as compared to the Sutlej River Basin.