Runoff Estimation and Identification of Water Harvesting Structures for Groundwater Recharge Using Geo - Spatial Techniques

A geo-spatial study was conducted to estimate the runoff by Soil Conservation Services ? Curve Number (SCS ? CN) method, in Nagapattinam Taluk (areal extent of 303.96 km2 ), Tamil Nadu, India. In this study, the spatial data of land use (2007) was derived from satellite images. A hydrological soil group thematic map was also prepared using ArcGIS 9.3. The thematic maps were overlaid with each other and assigned the SCS? CN values, and the runoff potential map was prepared on the basis of curve number classes. The highest, moderate and low runoff potential zones (2007) were obtained, and the area covered under each category was found to be 165.96, 121.65 and 15.81km2 , respectively. To determine the suitable locations of rainwater harvesting structures, land use, soil group and slope map were overlain. From the overlain map attributes viz., soil, land use and slope, the suitable locations of rainwater harvesting structures like check dams (84 Nos.), percolation ponds and nalla bunds (76 Nos.) and farm ponds (20 Nos.), respectively, were found. The geospatial identified structures were validated through existing structures in the study area with their GPS coordinates, and it was found that some of the structure locations were exactly in line.