Andreas Hartmann , Scott Jasechko, Tom Gleeson, Yoshihide Wada, Bartolomé Andreo, Juan Antonio Barberá, Heike Brielmann, Lhoussaine Bouchaou, Jean-Baptiste Charlier, W George Darling

Groundwater pollution threatens human and ecosystem health in many areas around the globe. Shortcuts to the groundwater through 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 such concentrated recharge on water quality remains poorly understood. Here we apply a continental-scale model to quantify the danger of groundwater contamination by degradable pollutants through concentrated recharge in carbonate rock regions. We show that in regions where concentrated recharge takes place, the percentage of non-degraded pollutants in groundwater recharge increases from <1% to around 10-50%. In those regions, pollutants like Glyphosate can exceed their permissible concentrations by up to 19 times when reasonable application rates are assumed. Our results imply that in times of continuing industrial agricultural productivity, shortcuts to the groundwater may result in a widespread and substantial reduction of usable groundwater volumes.