Assessment of the relative impacts of climate changes and anthropogenic forcing on spring discharge of a Mediterranean karst system

Abstract

The Mediterranean region is a climate change hotspot where the rate of climate change exceeds the global mean. The rapidly changing climate in combination with an increase in anthropogenic pressures cause water resources in the Mediterranean basin to become increasingly scarce. Modelling future water resource availability considering both climate and anthropogenic changes on karst catchments remains a major challenge in the field of hydrology. The purpose of this study is to assess the relative effects of climate change and anthropogenic forcing on the spring discharge of a Mediterranean karst system by coupling 12 climate model simulations under two emission scenarios (RCP 4.5 and RCP 8.5) with three hydrological models and four scenarios of future groundwater extraction for drinking water supply (no abstraction, present-day abstraction, +50% abstraction and + 100% abstraction at horizon 2100). The study area is the Oeillal spring’s karst catchment which is located at the Fonfroide-Monredon massif located in Southern France. The periods of spring drying-up can increase up to 30% according the RCP 4.5 and up to 70% according the RCP 8.5. This may be aggravated by groundwater abstraction in the area which, combined with climate change, could contribute to double the length of spring drying-up period in the worst scenario. The main results of the study suggest that climate change has a major effect on the future evolution of the Oeillal spring’s discharge and that groundwater abstraction constitutes a secondary but non-negligible factor which increases the occurrence of drying-up of this Mediterranean spring.