Geophysical methods are scientific techniques used to investigate the subsurface properties of the Earth without drilling. These methods are essential in locating groundwater aquifers, determining depth, thickness, and quality of water-bearing layers, and supporting sustainable groundwater management.
1. Importance of Geophysical Methods in Groundwater Studies
a) Identification of Aquifers
- Helps in locating porous and permeable layers (aquifers) that can store and transmit groundwater.
- Useful in distinguishing between water-bearing and dry zones.
b) Depth Estimation of Water Table
- Accurately estimates the depth of the water table, which helps in proper well placement and construction.
c) Delineation of Aquifer Boundaries
- Defines the horizontal and vertical extent of aquifers.
- Prevents over-extraction by identifying recharge zones and aquifer limits.
d) Assessment of Groundwater Quality
- Some geophysical signals (like resistivity) vary with salinity and mineral content, helping estimate water quality.
2. Common Geophysical Methods Used
a) Electrical Resistivity Method
- Measures resistance of underground materials to electrical current.
- Water-bearing zones generally show low resistivity.
- Widely used for groundwater surveys in India.
b) Seismic Methods
- Detect subsurface layers and fractures that can store water by measuring how seismic waves travel.
c) Magnetic and Gravity Surveys
- Useful in regional-scale mapping of groundwater systems.
- Identify basins and fractures favorable for groundwater storage.
3. Advantages of Geophysical Methods
- Non-invasive and eco-friendly (no digging required).
- Cost-effective compared to random drilling.
- Helps in planning borewells and avoiding failures.
- Supports groundwater resource mapping and recharge planning.