| Summary: | Sustainable groundwater management by artificial recharge of aquifers has become a possible resolution for increasing depletion and deterioration of groundwater in several river basins across the word. The present study identifies suitable sites to adopt possible aquifer recharge structures in the Vamanapuram River Basin (VRB), South India, where water scarcity and groundwater declines caused parts of the basin to fall in the semi-critical category. The potential of the basin for suitable artificial recharge were investigated by analysing the geo-environmental variables using remote sensing, geographical information system and analytic hierarchy process (AHP) technique. The geo-environmental variables considered for the analysis includes plan curvature, profile curvature, land use/land cover, aspect, distance from streams, relative relief, geology, geomorphology, slope angle, available space for recharge, lineament density, sand percent, rainfall and drainage density. The slope stability assessment and potential recharge zonation was carried out using weighted overlay analysis by assigning the comparative weights to different thematic layers with the help of the multi-criteria decision-making tool of AHP technique. The results of the slope stability analysis were validated using existing slope failure data. The receiver operating characteristic curve (ROC) and area under the curve (AUC) value were used as a performance indicator for the validation of slope stability map. Further, suitable locations in the basin for four site-specific recharging mechanisms viz., rainwater infiltration pits, percolation ponds, injection wells and pond-cum-injection wells were identified using a rule-based approach. It is estimated that an annual volume of 2489.3 Mm3 of water is available to recharge groundwater in VRB, which accounts for nearly 19.2% of the precipitation in the basin. The potential for artificial recharge in VRB is found to be controlled significantly by factors such as geology, geomorphology, slope and available space for recharge. The slope stability analysis shows that about 94.3% of the basin fall under stable zone category and are safe for the construction of aquifer recharge structures, which was further validated with a prediction accuracy of 89.2%. It is estimated that 22,17,639.76 (m3/year) volume of water is available for recharge in VRB; however, the average recharge rates in the basin varies spatially. Western and north-central parts of the basin are found to be suitable for the construction of rainwater infiltration pits and injection wells and percolation ponds respectively, whereas the central parts are found to be suitable for the implementation of percolation ponds and pond-cum injection wells. The outcome of this study can be used for the planning of sustainable groundwater development and regional management of the river basin.
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