An evaluation of climate change impacts on groundwater flow in the Plana de La Galera and Tortosa alluvial aquifers (Spain)

Abstract

The increasing evidence of climate change motivates the need of quantifying its impacts on groundwater resources and their associated ecosystems to minimize its negative effects. Climate change is expected to produce an increase in temperature and a decrease in precipitation in many places of the Iberian Peninsula. These changes will reduce the groundwater resources. The rise of the sea level in coastal aquifers is an additional threat to groundwater resources. The effects of climate change in the groundwater resources of the Plana de La Galera and Tortosa alluvial aquifers near the Ebre River Delta have been evaluated with water balance and groundwater flow models and three regional climate models by taking into account simultaneously the reduction of groundwater recharge and the rising of the Mediterranean Sea level. The models were calibrated with historic data from 1998 to 2008 and then used to simulate the impacts of climate change in groundwater levels in the simulation periods 2020–2050 and 2069–2099. The climate models predict an increase in average temperature and a decrease in rainfall in the simulation periods 2020–2050 and 2069–2099 compared to the control period 1960–1990. Consequently, the mean annual recharge in the Plana de La Galera aquifer will decrease 23 % in the period 2020–2050 and 27 % in the period 2069–2099 compared to the mean annual recharge in the control period 1960–1990. The recharge in the Tortosa alluvial aquifer will decrease 22 % in the period 2020–2050 and 31 % in the period 2069–2099. The predicted changes in recharge vary significantly from rain-fed to irrigated (drip and flood) areas. In rain-fed areas, the decrease in groundwater recharge is approximately equal to the decrease in precipitation. According to the models here developed, the reduction in recharge will lead to a significant lowering of hydraulic heads in the recharge areas of the Plana de La Galera aquifer for the period 2069–2099. Near the Ebre River Delta, however, groundwater heads will increase slightly due to the rise of the mean sea level.