Quantifying the significance of basin parameters and hydro-climatic factors to water and sediment yields across spatio-temporal scales in mountainous river Basin, Sikkim

Abstract

The precise identification of basin characteristics and climate factors that plays a significant role in determining water and sediment yield is of paramount importance. However, due to the enormous complexity associated with the hydrologic cycle, it is usually challenging to extricate the influence of individual parameters on the combined water and sediment yield responses. To accomplish this, a combined hydrological modelling and statistical approach was adopted in this study. The Soil and Water Assessment Tool (SWAT) model was adopted to simulate different components of the watershed and the results were utilized in Boosted Regression Trees (BRTs) to analyze the contribution of different parameters to water and sediment yield at spatio-temporal and seasonal scales in the upstream Teesta River basin. The outcomes of the analysis showed that precipitation and baseflow play a crucial role in regulating the water yield at all spatio-temporal scales. On the other hand, precipitation alone has a key role in determining the sediment yield, especially at the daily (49.30%) and monthly (21.14%) temporal scales. The relative contribution of the remaining parameters at a yearly temporal scale, and small and intermediate spatial scales showed relatively close results with an exception at the large basin scale (precipitation alone by 35.88%). The average contribution of actual evapotranspiration was found to be less on both water and sediment yield prediction in all spatio-temporal scales considered. The analysis also revealed that the precipitation, baseflow, and minimum temperature play a key role in regulating the water and sediment yield in both monsoon and non-monsoon seasons, whereas the contribution of maximum temperature and snowmelt was found less during monsoon and non-monsoon seasons. The outcomes of this study may assist policymakers and water managers in rational water management goals as well as in coping with soil degradation issues.