Hyderabad : Scientists in India have found an easy way to detect groundwater in semi-hard rock areas. The new way, which the scientists claim is also economical, uses electricity and could improve the siting of borewells to improve clean water supply in the developing world.
Hyderabad-based National Geophysical Research Institute scientists claim electrical conductivity measurements of hard rock terrain recorded before and after the monsoon season can reveal differences that show where water accumulates most in subterranean rock fissures.
By comparing the data with other geological measurements and tests, regions of underground water can be located without additional test drilling and pinpoint the best location for borewells.
The scientists -- PD Sreedevi, Dewashish Kumar and Shakeel Ahmed -- said details of the approach are outlined in the International Journal of Hydrology Science and Technology this month.
A statement said understanding hard rock aquifers relies on hydrology of fractured rock and knowing details of the subterranean environment. Data is commonly obtained through drilling test boreholes or investigating underground openings.
Such work is hazardous and time consuming and does not necessarily reveal the most appropriate site to sink a water well. However, anomalies in electrical conductivity measurements of which many have been made in various regions might be useful in finding the most abundant sources of groundwater.
The researchers demonstrated how effective the approach might be in correlating information from 25 boreholes in the Maheshwaram watershed situated in the Ranga Reddy district of Andhra Pradesh, India, about 30 kilometers south of Hyderabad, covering an area of about 60 square kilometers.
The area is semi-arid with average annual rainfall of 750 millimeters. The bedrock is mostly granite.
The team points out that, based on the detailed geological and hydrogeological studies, the aquifer is classified as a two-tier coupled system with weathered and fractured layers that exist over almost the entire area. However, due to over-exploitation, the groundwater levels have affected the weathered layers and groundwater flow is currently in the fractured rock aquifer.
There are no rivers feeding the aquifers so the system relies on the monsoon to for replenishment.
Our approach is fast and cost effective and could be very useful as a screening tool prior to conducting hydraulic testing and water sampling, the scientists claimed.