Analysis of Human Activities, Built-Up and Rainfall Impacts on Groundwater Potential Zones Using GIS and AHP Techniques: A Case of Karaman River, Southern Western Ghats, India

In recent years, realizing groundwater prospects using geospatial technologies gained attention due to their rapid and cost-effective nature for better management. The present study attempts to delineate the groundwater potential zones (GWPZs) of a tropical mountainous river, the Karamana, in southern India, using geographical information system (GIS) and analytical hierarchical process (AHP) techniques. A total of ten thematic layers viz. geomorphology, lithology, land use/land cover (LULC), lineament density, drainage density, rainfall, soil, slope, roughness, and topographic wetness index are prepared in a GIS environment. The AHP is used to assign the weights to all ten thematic maps based on their characteristics to influence the groundwater. The composite GWPZ map is divided into five distinct categories, i.e., very low (0.23%), low (12.87%), moderate (46.1%), high (40%), and very high (0.23); additionally, the description highlights the presence of low GWPZ in the eastern and some middle regions due to the influence of slopeness (24.83–53.22 degrees) and stream order pattern in the study area. The GWPZ map is validated with available groundwater level data of observation wells at different parts of the study area. Further, LULC features and rainfall are identified as dominating control factors of GWPZ which are operated by human activities and climate change effects respectively. For future management and strategies concerning GWPZ, these impacts are assessed and adjusted by modifying the controlling factors according to their recent temporal changes: (i) altering rainfall levels by one standard deviation from the long-term average, (ii) expanding the built-up area within the LULC features by 5% and 10%. The changes in GWPZ due to perturbing the controlling factors suggest that increasing the rainfall and rise in built-ups results in abruptly increasing the very low and low GWPZ by reducing the medium and high potential zones. The framework and results of the present study will be valuable for both government and non-government initiatives, serving as a useful pre-decisional tool for managing and preserving groundwater and rainwater systems in India.