Location map

Key findings

• Aquifer architecture: the aquifer is organized into a weathered/saprolitic layer overlying a fractured granite layer, with the most transmissive zone near their interface and a network of predominantly sub-horizontal fractures.
• Groundwater recharge and flow: stable isotopes showed that groundwater is mainly derived from present-day monsoon rainfall, with evaporation during infiltration through the soil and saprolite and spatially variable recharge.
• Multi-scale characterization: combining boreholes, geophysics, hydraulic tests and groundwater-level monitoring made it possible to characterize the geometry and hydraulic properties of the heterogeneous weathered–fractured aquifer from the well to the catchment scale.
• Impact of intensive pumping: long-term monitoring demonstrated a persistent decline in groundwater levels under intensive irrigation pumping, leading to the drying of springs and streams and progressively deeper water tables.
• Groundwater management: the observatory provided a quantitative basis for estimating specific yield and recharge, assessing groundwater budgets, and developing management approaches for heavily exploited crystalline aquifers.

Hydrogeological model

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