Streamflow Assessment of Mountainous River Basin Using SWAT Model

Abstract

The topography can have a substantial effect on the streamflows of the mountainous river basins. The Sutlej river basin (SRB) is mountainous, often with streamflows affected by its natural topography, which ranges from 443 to 6988 m. The hydrological modeling tools used for streamflow assessment in such river basins should accommodate the elevation differences or bands. The Soil and Water Assessment Tool (SWAT) model framework, coupled with the help of Remote Sensing (RS) and Geographical Information System (GIS) capable of fitting the elevation bands in the model. The present study demonstrates the performance of the SWAT model through a statistical performance indicator, namely, Kling-Gupta efficiency (KGE), while assessing the monthly streamflows in the SRB with the consideration of the elevation bands and without them. Optimal model parameters and the level of uncertainty are calibrated through the SUFI-2 algorithm by taking KGE as an objective function. The results obtained with the elevation band use in the SWAT model proved better compared to the model without elevation band use. The model performance statistics, such as KGE, R², p-bias, and p-factor, show 0.91, 0.83, 2.30, and 0.82, respectively, with the use of elevation band, and 0.21, 0.47, 0.85, and 0.01, respectively, for without the elevation band use in the model, signifies the SWAT model poorly performed without the use of elevation band or natural topography of the river basin. It confirms that the topography shows a significant effect on the streamflows of the mountainous river basins. This work will help the researchers to make them aware of the limitations of the SWAT model use while applying it to the mountainous river basins.