Runoff Volume Estimation by SCS-CN Method Through Arc-GIS Approach

The salient resources of water for discharge of groundwater in a watershed or catchment area are rainfall and rainfall runoff. The primary source of groundwater recharge is rainfall. Runoff in the watershed or catchment area affected by geomorphologic feature principally, land use change affects the surface runoff volume over and rate of runoff considerably. This project aims to estimate the runoff volume over Gangadhara watershed (289.29 km²), Telangana by one of the methods called Soil Conservation Services (SCS)–Curve Number (CN) method. In this method, alternate land use/land cover (LULC) and soil type shape files were first obtained and compiled using by remote sensing (RS) and geographic information system (GIS) techniques. Then, hydrologic soil group (HSG) maps will be developed by interpreting formative elements by soil taxonomy. Available rainfall data of the past 30 years (1988–2018) from rain gauge station of Gangadhara watershed is collected and screened to consistency and accuracy and is linked to GIS database. Based on soil and rainfall conditions of a watershed, the antecedent soil moisture condition (AMC) is found to be AMC-I, i.e. dry condition. By using relevant equations, the runoff volume over the watershed estimated is 0.81 km³.