Gangrel Dam, also known as the R.S. Sagar Dam, is located in Chhattisgarh, India. It is built across the Mahanadi River. It is located in Dhamtari district,about 15 km from dhamtari and about 90 km from Raipur. It is the longest dam in Chhattisgarh. This dam supplies year round irrigation, allowing farmers to harvest two crops per year. The dam also supplies 10 MW of hydro-electric power capacity.