Widespread underestimation of the danger of groundwater contamination by shortcuts into aquifers

Groundwater pollution threatens human and ecosystem health in many areas around the globe. Shortcuts to the groundwater through enlarged cracks and fissures, often referred to as concentrated recharge, are known to transmit short-lived pollutants into carbonate aquifers endangering water quality of around a quarter of the world population. However, the large-scale impact of concentrated recharge on water quality remains poorly understood. Here we apply a continental-scale model to quantify for the first time the danger of groundwater contamination by degradable pollutants through concentrated recharge in carbonate rock regions. We show that concentrated recharge is the primary reason for the rapid transport of contaminants to the groundwater, increasing the percentage of non-degraded pollutants from <1% in areas without concentrated recharge to around 20-50% in areas where concentrated recharge is present. Our findings are most pronounced in the Mediterranean region where agricultural pollutants in groundwater recharge like Glyphosate can exceed allowed concentrations by up to 19 times. Our results imply that in regions where shortcuts to the groundwater exist, continuing industrial agricultural productivity to optimize food production may result in a widespread reduction of available drinking water and harm ecosystem services more intense than presently available large-scale modelling concepts suggest.