Groundwater modelling requires data from electrical resistivity surveying and pumping test, which consumes more time and cost for its collection for a larger area. In this study, using remote sensing data and GIS tools, a sequential process is proposed for finding the suitable vulnerable smaller area for groundwater modelling from a relatively larger area. The chosen larger area, Cheyyar river basin, Tamil Nadu, India spreading 4358 km2, has groundwater decline due to aquifer groundwater exploitation. Groundwater potential zone with river basin as boundary and stage of groundwater development with firrka boundary are used for this study. For comparison, 56 firrkas covering the entire river basin were reduced to 26 firrkas, with at least 95% preserved area after reducing along the river basin boundary. Groundwater potential zones were converted to a firrka-wise representative potential zone by considering mode as a central tendency. As all the firrkas come under the moderate category, it was further reclassified into good-skewed-moderate, moderate and poor-skewed-moderate. The combinational class was developed by combining the two category maps for each firrka. The over-exploited and critical categories under good-skewed-moderate and over-exploited under the moderate category were considered vulnerable combinations. A total of eight firrkas come under the vulnerable category. Based on data availability and data collection feasibility in the vulnerable firrkas, Kelur's moderate overexploitation category is considered a smaller vulnerable area for groundwater modelling study.
