Groundwater Potential Zone Delineation Using Multi-criteria Decision-making Approach: A Case Study

Over-exploitation of groundwater from coastal aquifers causes seawater intrusion and depletion of freshwater resources. As 40 percent of the world's population live within 100 km of the coast. This will increase the demand for potable water in coastal aquifers. Hence, it is essential to evaluate the sources of fresh-groundwater potential and productivity in coastal aquifers. Nowadays, integrated studies based on geographic-information systems play a major role in groundwater-exploration studies. Thus, the current study was carried out with the objective to delineate groundwater potential in the Nambiyar river basin in Tamil Nadu's southeast coastal area, where groundwater is in a critical condition. In order to improve groundwater recharge, it is very important to identify possible recharge areas. A novel work of the integration of remote sensing, geographic information system (GIS) and multi-criteria decision-making approaches of analytical hierarchical-process methodologies (AHP) was used in the present study. A total of 11 thematic layers, such as slope, curvature, soil, roughness, topographic-wetness index, drainage density, land use/land cover, geology, geomorphology, lineament density and rainfall, were generated for delineating groundwater potential zones. All the thematic maps are weighted using AHP based on the attributes of the classes and the potential capacity of their water supply. The demarked region of groundwater potential was validated by comparing pre-monsoon and post-monsoon groundwater levels. The groundwater potential zone map was classified into five categories: very high, high, moderate, low and very low. Areas with very high and very low potentials are delineated only in very limited areas. 64% of the regions are covered under the moderate-potential zones. The low-and high-groundwater potential zones are delineated at 22% and 14%, respectively.