Fractured crystalline-rock aquifers are among the most heterogeneous groundwater systems. Their functioning results from the interaction between weathering, fractures, recharge, surface waters and groundwater flow at different spatial scales. Over several decades of field studies in India, Africa and Europe, I investigated different components of this system. I describe them as six pieces of a hydrogeological puzzle.

Each piece addresses a fundamental question. Together, they lead to an integrated conceptual model of fractured and weathered crystalline-rock aquifers.

The puzzle is solved here