Piece 4 - Groundwater–Surface Water Interactions
Is the river feeding the aquifer — or the aquifer feeding the river?
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Recharge is one of the most difficult components of the groundwater budget to quantify in semi-arid crystalline aquifers.
The double water table fluctuation method
A two-step method combining groundwater budgets and water-table fluctuations: the dry season is used to estimate specific yield, while the wet-season water-table rise is then converted into natural groundwater recharge.
Key findings
- Groundwater recharge can be quantified from long-term water-table fluctuations, using complementary approaches such as the Double Water Table Fluctuation and groundwater budget methods.
- Recharge is highly seasonal, closely linked to the monsoon rainfall regime in the semi-arid crystalline-rock aquifers of southern India.
- Recharge is spatially heterogeneous, reflecting the strong heterogeneity of the weathered and fractured profile.
- Fracture distribution strongly controls recharge pathways, with preferential infiltration occurring where fractures provide hydraulic connections between the surface and the transmissive fractured layer.
- The weathered zone plays a dual role, acting both as a temporary groundwater storage reservoir and as a buffer controlling the transfer of recharge towards the underlying fractured aquifer.
- Borehole observations revealed distinct recharge dynamics and flow paths, providing a basis for understanding how artificial recharge structures interact with the heterogeneous crystalline aquifer.
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Managed aquifer recharge
From natural recharge to managed rechargeThe understanding of infiltration and groundwater storage was also applied to artificial/managed recharge in fractured basement aquifers.
Managed aquifer recharge (MAR) can enhance groundwater replenishment, but its efficiency depends strongly on the local hydrogeological structure and connectivity of the fractured zone. Your work included both the assessment of recharge structures and their long-term sustainability.
Recharge cannot be represented as a uniform flux: it depends on climate, land use, soil properties, topography and preferential infiltration pathways.