• Energy Research

A comparative study on climate change and its impacts on coastal aquifers is performed for three Mediterranean areas. Common climate scenarios are developed for these areas using the ENSEMBLES projections that consider the A1b scenario. Temperature and precipitation data of three climate models are bias corrected with two different methods for a historic reference period, after which scenarios are created for 2020–2050 and 2069–2099 and used to calculate aquifer recharge for these periods based on two soil water budget methods. These multiple combinations of models and methods allow incorporating a level of uncertainty into the results. Groundwater flow models are developed for the three sites and then used to integrate future scenarios for three different parameters: (1) recharge, (2) crop water demand, and (3) sea level rise. Short-term predictions are marked by large ranges of predicted changes in recharge, only showing a consistent decrease at the Spanish site (mean 23 %), particularly due to a reduction in autumn rainfall. The latter is also expected to occur at the Portuguese site, resulting in a longer dry period. More frequent droughts are predicted at the Portuguese and Moroccan sites, but cannot be proven for the Spanish site. Toward the end of the century, results indicate a significant decrease (mean >25 %) in recharge in all areas, though most pronounced at the Portuguese site in absolute terms (mean 134 mm/year) and the Moroccan site in relative terms (mean 47 %). The models further predict a steady increase in crop water demand, causing 15–20 % additional evapotranspiration until 2100. Scenario modeling of groundwater flow shows its response to the predicted decreases in recharge and increases in pumping rates, with strongly reduced outflow into the coastal wetlands, whereas changes due to sea level rise are negligible.

AbstractThere are about 175 abandoned mining sites in Portugal, of which about 60 are old uranium workings. The Castelejo mine is an old uranium located about 2km W of Vila Cortês da Serra, in Guarda district, on the River Mondego basin. In geologic terms, the mine is located in medium-grained two-mica monzonitic granite, with porphyroidal tendency. Exploitation started with two open cast mines between 1979 and 1990 which produced about 132 tonnes U3O8. From 1992, production started to be carried out through the in situ H2SO4 leaching of the mine’s low-grade materials. The superficial and groundwater circulation are structurally conditioned by the intense fracturing in the area. Two exploratory geophysical field campaigns were conducted in order to characterize the fracturing. The first was a VLF survey that allowed us to identify major fault systems that may provide paths for groundwater flow. From the second campaign, which was an RMT survey conducted at a fault gauge which records the mine natural gradient flow, we obtained the resistivities and thicknesses of the weathered granite material. The profiles obtained show that resistivity declines with increasing depth. This fact may arise from natural causes – the material which fills the fault gauge is more weathered at depth than on the surface – or it may indicate contamination at depth, due to acid mine drainage.