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Supply of sustainable water is a priority for urbanization of the country. Managed aquifer recharge (MAR) is recommended to enhance the groundwater resources, but finding the favorable site for MAR is quite challenging, particularly, in urbanized karst terrains because of highly heterogeneous and anisotropic properties of carbonate aquifers. The expansion along Naya Raipur is posing a severe threat to its groundwater resources by altering the hydrological framework in the area. In this work, we characterize the unsaturated zone for finding potential pathways for MAR in karst terrain of central India by using hydro-geophysical techniques. Sub-surface geophysical investigations including electrical sounding and profiling, captured the shallow surface of the area to the depth of around 40 m. The Wenner–Schlumberger and gradient methods could decipher strong lateral and vertical anomalies. The low resistivity in the unsaturated zone, as compared to the high resistivity of limestone bedrock is the main path for infiltration. The low resistivity anomalies in the 2D inverted sections might be water filled conduits or solution channels with uncertain geometry. Hydrogeological heterogeneity based on geophysical data helped to locate the favourable zones for construction of MAR structures. The Chokra Nala in the Telibandha area of Raipur is the favorable zone along which MAR could be more effective in replenishing the groundwater. The Telibandha lake area with the indication of the presence of hidden mafic dyke later intruding the limestone after its deposition, was also inferred from the geophysical data. Highlights: Characterizing the unsaturated zone for finding potential pathways for MAR in karst terrain using hydro-geophysical techniques. Establishing MAR along the solution channels, conduits and fracture network. 3D fracture system in limestone from 2D ERT profiles. Mapping hydrogeological heterogeneity based on geophysical data. [ABSTRACT FROM AUTHOR]

A comprehensive geophysical and petrological study was carried out at Giddalur area in Prakasam district, Andhra Pradesh, which is geologically a highly deformed area and is difficult to delineate the aquifer zone(s). The task was to find out the exact rock type in which aquifer is concealed as well as to delineate the aquifer zone, which can yield sufficient quantity of water. The resistivity models derived from geophysical dataset were interpreted in terms of hydrogeology and the results revealed substantial resistivity contrast of the geological formations within the study area. We have delineated two major groundwater potential zones based on this study. These zones were tapped at different depths in diverse rock types. Drilled hand specimens (rock cuttings) were not adequate, so these specimens were petrographically studied to reveal the exact contact zones of the rock type. On integration of the geophysical and the petrographic results, it was illustrated that two aquifer zones were struck at a depth of 92 and 122 m between shale-phyllite and phyllite-quartzite, respectively. These findings were correlated, which matched with the lithology of the drilled borehole. This integrated approach will be helpful in strategy for groundwater assessment as well as prospecting groundwater resources in different geological terrain. [ABSTRACT FROM AUTHOR]

Raipur of Chhattisgarh state, central India, is facing water problems due to rapid urbanization and altered hydrological processes despite adequate rainfall. Deteriorated surface water, diminished recharge and elevated pumping have reduced water availability in the region. Therefore, proper measures like managed aquifer recharge (MAR) need to be successfully implemented to conserve rain water for long-term sustainability. Hydrogeological data, combined with geophysical investigations lead to the construction of a conceptual model of the Chandi limestone aquifer for this purpose. The results indicate that the compact and massive limestone has negligible primary porosity, but solution weathering (karstification) has developed secondary pores at variable depths that favour recharge, groundwater storage and movement. The study helped to locate potential recharge sites that have significance in optimizing MAR structures such as check dams and injection wells. The hydrogeological model has a great significance in managing these complex and heterogeneous aquifers for better future water supply in the region. [ABSTRACT FROM AUTHOR]