Increased Vegetation in Mountainous Headwaters Amplifies Water Stress During Dry Periods

The dynamics of blue and green water partitioning under vegetation and climate change, as well as their different interactions during wet and dry periods, are poorly understood in the literature. We analyzed the impact of vegetation changes on blue water generation in a central Spanish Pyrenees basin undergoing intense afforestation. We found that vegetation change is a key driver of large decreases in blue water availability. The effect of vegetation increase is amplified during dry years, and mainly during the dry season, with streamflow reductions of more than 50%. This pattern can be attributed primarily to increased plant water consumption. Our findings highlight the importance of vegetation changes in reinforcing the decrease in water resource availability. With aridity expected to rise in southern Europe over the next few decades, interactions between climate and land management practices appear to be amplifying future hydrological drought risk in the region.This work was supported by projects CGL2017-82216-R, PCI2019-103631, and PID2019-108589RA-I00 financed by the Spanish Commission of Science and Technology and FEDER; CROSSDRO project financed by AXIS (Assess-ment of Cross(X)-sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission and INDECIS which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462). Dhais Peña-Angulo received a “Juan de la Cierva” postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC). Miquel Tomas-Burguera received a “Juan de la Cierva” postdoctoral contract (FJCI-2019-039261-I Spanish Ministry of Science and Innovation). C. Azorin-Molina and S. Grainger. acknowledge funding from the Irish Environmental Protection Agency grant 2019-CCRP-MS.60. C. Juez acknowl-edges funding from the H2020-MSCA-IF-2018 programme (Marie Sklodows-ka-Curie Actions) of the European Union under REA grant agreement, number 834329-SEDILAND