Kabita Lepcha
Abstract
Surface runoff significantly affects the hydrological characteristics and soil erosion of the river basin. Rainfall, land use land cover and soil texture determines the amount of surface runoff. The estimation of surface runoff is one of the prerequisite for sustainable watershed management. The Soil Conservation Service- Curve Number (SCS-CN) method is one of the most widely used methods for the surface runoff estimation. In the present study, Chhota Rangit river basin located in the Darjeeling Himalaya has been selected for the estimation of the surface runoff by SCS-CN method. The thematic layers for important parameters such as soil texture, land use/land cover and rainfall has been generated in ArcGIS environment. The curve number (CN) polygon wise has been estimated using a combination of land use, soil, and antecedent soil moisture condition (AMC). This study reveals that SCS-CN method coupled with Remote Sensing and GIS is capable of simulating runoff pattern and runoff volume successfully for the mountainous watershed of Chhota Rangit River. The result shows that the volume of surface runoff varies from 16401.1 mm in 1991, 18222.03 mm in 2001, 16505.61 mm in 2011 and 14832.2 mm in 2022. It is observed in this study, that spatial and temporal distribution of the surface runoffs of the river basin has changed significantly due to changing land use and rainfall pattern.