Estimating Change in Runoff Caused by Land-Use Change over a Period of 13 Years in a Watershed in Keonjhar District (Odisha) using Gis Based SCS-CN Method

Change in land-use is an inevitable phenomenon that occurs within a landform over time, especially in human-intercepted areas. A watershed of 380.5 Km2 consisting major segment of mining and allied operations of Gandahamardhan Iron Ore mines was selected in the Keonjhar district of Odisha. The paper aims to estimate the difference in the runoff caused by the landuse change in the watershed over a period of 13 years (2008-2021). All the other factors such as Hydrological Soil Group (HSG), precipitation and topography were kept constant in order to understand the variation in runoff caused solely due to land-use change. The runoff estimation was done using Soil Conservation Service- Curve Number (SCS-CN) method and CN values for normal conditions (CNII) values were used for the calculation and incorporated in GIS platform. 16.62% increase in area under cropland, 48.5% increase in area under barren land, 21.86% decrease in area under woods and 0.76% increase in area under woods-grass combination was observed in 2021, keeping 2008 as the base year. A resulting increase in the runoff by 2.38%, 1.59%, 1.65% and 2.16% was observed in June, July, August and September of 2021 as compared to the corresponding values of runoff in 2008. Even though the range of runoff depth remained constant for both years (76.99 mm - 193.99 mm), but the mean runoff increased in 2021, as a result of the land-use change.