Climate change impact on groundwater resources of a hard rock mountain region (Serra da Estrela, Central Portugal)

Water resources in mountain regions are at risk due to demographic and economic growth and climate change. This paper presents an evaluation of the impacts of climate change on the groundwater resources of Serra da Estrela Mountain (Portugal). The changes in the water resources in the last 30 years of the twenty-first century have been evaluated with respect to the hydrometeorological conditions of the control period 1975–2005. The predictions for the period 2069–2099 were made by using the Representative Concentration Pathways RCP4.5 and RCP8.5, which are two climate scenarios of the EURO-CORDEX project. The climate scenarios RCP4.5 and RCP8.5 cover a reasonably wide range of possible future trends. The impacts of the climate change have been assessed by using the simulated daily temperature and precipitation values from the climatic models and by solving the daily hydrological water balance model with the code VISUAL-BALAN. The mean annual temperature for the RCP4.5 and RCP8.5 scenarios will increase 3.1 and 5.4 °C, respectively. The increase of temperature in the winter will reduce snow precipitation and favor the melting of the snow cover in the highest sub-basins. The mean annual precipitation will decrease from 8% (RCP4.5 scenario) to 15% (RCP8.5 scenario). The mean annual snow precipitation will decrease drastically from 54 to 84%. The mean interflow and aquifer recharge will decrease from 12 to 22%. The mean streamflow will decrease from 10 to 18%. The largest decrease in monthly streamflows will occur from March to May due to the decrease of rainfall and snow precipitation. Monthly streamflows during the snow melting season will decrease from 37 to 45%. It can be concluded that the water resources in the Serra da Estrela mountain basin will be very vulnerable to the predicted changes in precipitation and temperature.