Satara, Solapur and Sangli in Maharashtra lie in the Deccan volcanic province, in the rain shadow region of the Western-Ghats. And the hard rock terrain also restricts water availability.
To locate and assess groundwater in the area, G. Gupta and team from the Indian Institute of Geomagnetism studied aquifers in the Mann River basin. There were many volcanic events in the region 65 million years ago. The resultant layers of porous rock can harbour water.
Rock, clay and subterranean water bodies have different electrical resistances. So the team used electrical resistivity to identify and assess subsurface water-bearing zones. They did 118 vertical electrical soundings to investigate subsurface geology and soil characteristics.
They found water-bearing zones at 20 and 40 meters. And deep confined aquifers below 40 meters. Some aquifers were up to 75 meters thick. The central and western areas of the river basin had good groundwater potential, say the researchers.
But the area has porous rocks and may allow fertilisers and chemicals to contaminate groundwater. Though most of the area had freshwater, lack of clayey materials allows fertilisers, pesticides and other chemicals to percolate into groundwater.
So they prepared thematic maps to evaluate the protective capacity and hydrologic properties of the aquifers. Only about 20% area had adequate clayey overburden to protect aquifers from contamination.
The report offers insights into groundwater exploration and identification of areas that need protection using scientific methods. Now there is a need to take steps to protect the valuable life sustaining resources underground.
Moreover, the mapping needs to be extended to other areas in the region, with similar geomorphological characteristics.
J. Earth System Sci. 128 (4): 78 (2019);
*The original version of this report was published in Current Science, 116 (11): 1783 (10 JUNE 2019)