AHP and geospatial technologies for identifying groundwater exploration target regions in Dindigul, southern India

Recent advances in space technology are being widely utilized in resource mapping and management as they provide a high level of accuracy over a short duration and at a lower cost, when compared to traditional methods. Remote sensing and the geographical information system (GIS) play a vital role in collecting and analyzing information used to map resources and earth surface features. For example, anthropogenic activities and climate change affect the natural interaction between the surface and ground water making the monitoring and management of groundwater resources mandatory for future sustainable development. In this study, we attempt to identify the groundwater potential zones in the Dindigul district of Tamil Nadu, India using these emerging technologies. To map regions with groundwater potential, the analytical hierarchical process (AHP) was used to assign weights to all classes in each thematic layer based on groundwater-influencing factors. The sub-features of every parameter were also ranked, using a pairwise comparison method, based on the groundwater-influencing factors and expert knowledge. The parameters selected for the analysis were geology, geomorphology, soil, land use/land cover, drainage density, lineament density, slope, rainfall, thickness of top-soil, thickness of fractured zone, thickness of weathered zone, topographic wetness index, roughness and curvature. The weighted overlay analysis method was adopted for all the thematic layers, with technical support from the AHP for assigning weightages. The results were classified into five categories viz., very high, high, moderate, low, and very low potential zones, and used to prepare a groundwater potential map. This map revealed a nuanced distribution of groundwater potential across the district, with varying degrees of potentiality in different regions. Very high potential zones occupy a minimal area (0.07%) but are strategically located in areas characterized by high weathered zone thickness and conducive soil characteristics. High potential zones cover a significant area (22.33%) and are dispersed throughout the district, with specific concentrations in regions featuring highly fractured zones and favorable geological attributes. Moderate potential zones (35.12%) are primarily located in the northeastern part of the study area, while low and very low potential regions cover 19.56% and 22.92% of the study area. The low and very low potential zones appear particularly in hilly terrains, with unfavorable top soil and geological conditions. The validation of the groundwater potential zone (GWPZ) map using the annual average water level data demonstrates a substantial match (60.53%) between the identified groundwater conditions and actual well depths, affirming the reliability and significance of the findings from this study.