Estimaion of runoff using SCS-CN method and geographic information system under changing climatic scenarios in Halia catchment

Climate change affects the hydrology mainly through changes in precipitation, temperature, evaporation, and it subsequently influences the temporal and spatial distributions of runoff and sediment. The study area, Halia river basin, located in Nalgonda district of Telangana state, covering an area of 3918.41 km2 was delineated in Arc-GIS and 416 sub-catchments were generated. The spatial and temporal variations of rainfall and runoff were analyzed. Most of the study area has normal rainfall less than 790 mm. Different thematic layers were intercepted in Arc-GIS and Soil Conservation Services Curve Number (SCS-CN) method was applied to estimate the runoff spatially and most of the catchment has runoff ranged from 10.5% to 17.5% of average annual rainfall during 1951 to 2020. Runoff was estimated under changing climatic scenarios using the ENSEMBLE data of CMIP 5. Major portion of the basin has runoff in the range 7.5% to 15.0% of annual rainfall during baseline period (1976 to 2005) and the runoff varied spatially from 7.5% to 20.0% of rainfall. By 2030s, under RCP 4.5, the runoff was predicted to increase by 0.60% to 6.80% of annual rainfall and under RCP 6.0, it is expected to increase by 0.59% to 6.53% of annual rainfall with respect to baseline. Changes in the climatic conditions are resulting in the uncertainty in rainfall distribution.