Location map

(a) Maheshwaram watershed with location of pumping borewells for irrigation (July 2002), (b) EHP (0.55 km²) site near Choutuppal village, with two clusters of monitored borewells

Key findings

• Groundwater flow is controlled by the weathered/fractured interface
  The most transmissive part of the crystalline aquifer is concentrated near the interface between the saprolite and fractured granite. This zone acts as a major preferential pathway for groundwater flow.
• The aquifer is highly compartmentalized and its connectivity changes with water level
  When groundwater levels fall, hydraulic connections between fractures become progressively disrupted, producing a discontinuous or compartmentalized aquifer. Thus, fracture connectivity is not fixed: it depends on the hydraulic state of the aquifer.
• Recharge is preferentially transmitted horizontally
  Experiments with the infiltration basin (MAR: Managed Aquifer Recharge) showed that recharge reaching the saprolite–bedrock interface can propagate laterally over the aquifer through a well-connected preferential pathway. The variable relief of this interface controls the amplitude and timing of groundwater-level responses.
• Tracer and hydraulic experiments revealed multi-scale transport processes
  The dense borehole network made it possible to combine pumping, slug, packer and inter-well tracer tests to characterize permeability, vertical connectivity, dispersivity and effective porosity. This provided a rare experimental view of how water and solutes actually move through a heterogeneous fractured crystalline aquifer.

Hydrogeological model

Conceptual fractured crystalline-rock aquifer model at the watershed-scale as a function of water level conditions: (a) under high water level conditions and (b) under low water level conditions.

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