Drip flow and gravity driven simulations of water transfer in vadose dolomite karst

English Abstract:

Recharge processes in a Mediterranean dolomite karst are studied on the basis of simulations and field measurements. Located 10 meters beneath the surface of a karst plateau, the Canalette's cave (Larzac, South France) offers a window on the karst vadose zone. To appreciate the various recharge processes, models are constrained with hydro-meteorological and gravity data, which are sensitive to the underground mass variation. The high weathering of the dolomite karst allows assuming that the vadose zone has a continuous porosity and permeability. Numerical simulations accounting for Richard's equations are performed; then, the influence of i) the matrix rock/cave interface and of ii) hysteresis and on the drip discharge and on the water content distribution within the vadose zone is assessed. The major water storage variations are clearly evidenced within the first 5 meters. A saturated zone is observed above the matrix rock/cave interface, which locally enhances permeability and generates downward flush mechanism. Finally, the recharge processes and the role of hysteresis evidenced from the local study are discussed at the basin scale to understand the dolomite karst singular recharge dynamic.