Disentangling the scarcity of near-natural Iberian hydrological resources since 1980s: a multivariate-driven approach

Abstract. A significant abrupt decrease of Winter Precipitation (WP) has been noticed in the Iberian Peninsula since the 1980s related to atmospheric drivers. This contribution assesses the long-term variability of water resources based on a multivariate-driven approach. For this purpose, the novel dataset of Near Natural Water Inflows to Reservoirs of Spain (NENWIRES) was created. Results confirm that Winter Water Inflows (WWI) have been modulated by the sudden decline in WP. These drastic reductions of WP/WWI were mainly controlled by the enhancement of the positive phase of the North Atlantic Oscillation (NAOi+). Nonetheless, our results also highlight the anthropogenic/physical causes contributing to the 1980s shift in the hydroclimate series. The rise of temperature, the cropland abandonment and forest extension provoked evapotranspiration gains and run-off weakening. NENWIRES most humid catchments registered the decrease of WWI promoted by NAOi+ persistence/frequency, while the land greening-up and ET rises explain the WWI losses in the Iberian semiarid environments. This contribution sheds some light on the recent debate about magnitude/drivers of streamflow declining over southern Europe. Therefore, it might help water planning with the goal of mitigating the climate change impacts affecting the water cycle.