Intensive irrigation buffers groundwater declines in key European breadbasket

Abstract

The Po Plain in northern Italy is a critical agricultural region and one of the largest water users in the European Union. Recent dry conditions have put future water resource availability into question. This study examines spatio-temporal variations in groundwater storage observed by the Gravity Recovery and Climate Experiment satellites and more than 1,000 groundwater wells from 2002 to 2022. We find that the rate of groundwater storage decline more than doubled from 2015 to 2022 as compared to the 2002–2022 rate. We also show that seasonal and long-term groundwater availability is strongly influenced by irrigation activities. Groundwater storage in irrigated areas is highly correlated to snow accumulation in the Alps and shows more stability as compared to non-irrigated areas, which experience dramatic declines during drought years. This indicates that inefficient irrigation practice, using water largely supplied by snowmelt, recharges underground aquifers and helps maintain high water tables, making aquifers underlying irrigated farmland resilient to the negative consequences of drought. These findings can help guide climate-driven adaptations to irrigation systems that account for the impact on groundwater recharge. This study provides evidence that agricultural irrigation artificially recharges the groundwater in the Po Plain, highlighting the importance of irrigation inefficiencies for groundwater recharge.