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.

Recharge cannot be represented as a uniform flux: it depends on climate, land use, soil properties, topography and preferential infiltration pathways.