A Preliminary Lumped Assessment of Pollution Risk at Aquifer Scale by Using the Mean Residence Time. Analyses of Potential Climate Change Impacts

Abstract

An assessment of the risk for groundwater pollution and vulnerability to pumping can help identify strategic groundwater bodies to define sustainable management measures of groundwater resources. In this paper, we propose a new method to make a preliminary estimation of the risk for groundwater pollution at the aquifer scale through the lumped turnover time index (T index). A new lumped index (L-RISK index) was defined to assess the significance of the risk for pollution at the aquifer scale. Both L-RISK and T indices were employed to calibrate a linear regression model that showed a good inverse correlation in the eight aquifers of the Upper Guadiana Basin (Spain). This novel method can be applied to analyze a wide range of aquifers with limited information in order to identify potential strategic aquifers. It also allows one to make a preliminary assessment of the impacts of climate change on L-RISK. The results showed a high variability of the T index in the eight aquifers (8–76 years). Three of them had significant greater mean T values, which could be considered to be the main strategic groundwater resources. In the future, the T index will increase between 8 and 44%, and the L-RISK will decrease in all aquifers (1–18%).