Assessing the potential groundwater recharge from precipitation in the Pyrenees in the global change context

The Pyrenees range is a transboundary region shared by Spain, France and Andorre whose water resources are diverse (snowmelt and rainfall runoff in a topographically variable context, groundwater in complex and heterogeneous aquifers) and poorly known. As many other mountain regions, this territory is particularly vulnerable to the impacts of climate change. In the framework of the PIRAGUA project, funded by FEDER through the EU POCTEFA Program, the potential groundwater recharge from precipitation was estimated over the last 30 years at the scale of the Pyrenean range.

 

Using the meteorological forcing data provided at high spatial resolution in the framework of the PIRAGUA Project, the effective rainfall was computed at the daily time step using three different simple water balance methods, including land use effect on evapotranspiration (crop coefficients method) over the 1981-2010 period. Resulting effective precipitation ranges from 50 to more than 2000 mm/year on average and shows strong differences between the east and west sides of the Pyrenean chain.

 

Potential groundwater recharge from precipitation was then estimated using an effective precipitation infiltration ratio derived from the comparison of the IDPR geomorphological index to the baseflow index extracted from selected river discharge time series over the Pyrenees. The resulting potential recharge was finally averaged at the groundwater bodies’ scale of the Pyrenean chain.

 

Corresponding potential groundwater resources were finally compared to groundwater uses estimated at the Pyrenean scale in order to 1) assess their respective importance in relation to water uses and 2) identify the sectors of the territory for which situations of tension on groundwater resources could already be observed, tensions which are likely to increase in the context of climate change.