Geo-electrical investigation for groundwater reserves in the Boranakanive Reservoir Catchment in Tumkur district, Karnataka, India

The groundwater resources have been under significant constraints due to excessive exploitation and climate change. It is imperative to comprehend these dwindling resources' characteristics, given their distribution and occurrence variability across the space and time. A semi-arid climate characterizes the study area and agriculture is the primary occupation, their reliance on groundwater is indispensable due to the lack of surface water sources and erratic rainfall patterns. Consequently, the study employed the Schlumberger array of 200 m-spaced half-current electrodes Vertical Electrical Sounding (VES) survey was conducted at 100 VES locations to identify groundwater potential zones. Further, curve-matching and correlation of lithologies have been carried out from various VES-soundings, and also generated pseudo-cross sections of the subsurface geometry. The results revealed the existence of five geoelectrical resistivity layers as follows layer 1–6 to 422 Ωm, layer 2–8 to 7708 Ωm, layer 3–4 to 37117 Ωm, layer 4–37 to 95059 Ωm, and layer 5–205 to 83142 Ωm. The iso-apparent resistivity maps of the study area reveal values ranging for the first layer 11Ωm - 333 Ωm, the second layer 23Ωm - 5347Ωm, the third layer 11Ωm - 26734Ωm and 10Ωm - 67250Ωm for the fourth layer. The present research determined that the third and fourth layer constitute the principal aquifers due to their fractured structures. As a result, these layers produce a significant quantity of groundwater in the north-eastern (NE) and southern (S) regions of the study region. As a consequence of these findings, further exploration and management of groundwater resources in the study areas can be carried out with valuable insight. • Schlumberger array of 200 m-spaced half-current electrodes VES survey conducted at 100 VES locations to identify GW reserves in study area. • Interpreted curve matching and correlating lithologies from various soundings to generate pseudo-cross sections of sub-surface geometry. • Key research finding is, 3rd and 4th layer constitute the principal aquifers due to their fractured structures and it indicates significant quantity of GW in the NE and southern regions of the study area.