A multi-model approach for improved simulations of future water availability at a large Eastern Mediterranean karst spring

Recent studies identified the Mediterranean as a region particularly vulnerable to climate change. Since a large fraction of the region’s water originates from karst aquifers, information about their future water availability is important for sustainable water management. This study presents an ensemble of 50 model chains considering five different realisations of the A1B ECHAM5 and HadCM3 climate projections, two different averaging methods to transfer the climate variables to the system scale and five different hydrological models that represent reasonable conceptualizations of the karst system. The ensemble is applied to Faria spring, a large Eastern Mediterranean karst spring in the West Bank. We show that for the near future (2021–2051) variability resulting from the different climate change projections and five different models is too large to draw conclusions on any significant change. In the remote future (2068–2098), variability decreases and our simulations suggest a decrease of water availability of −15% to −30%. We also assess the impact of recent pumping activities by running our hydrological models with recently measured data. There is a strong indication that the spring, which dried out in 2007, would have still yielded significant amounts of water if groundwater extractions had been limited. This calls for a better management of groundwater abstractions to meet future water needs in this drought-prone Mediterranean region.