More severe hydrological drought events emerge at different warming levels over the Wudinghe watershed in northern China

Assessment of changes in hydrological droughts at specific warming levels is important for an adaptive water resources management with consideration of the 2015 Paris Agreement. However, most studies focused on the response of drought frequency to the warming and neglected other drought characteristics, including severity. By using a semiarid watershed in northern China (i.e., Wudinghe) as an example, here we show less frequent but more severe hydrological drought events emerge at 1.5, 2 and 3 degrees C warming levels. We used meteorological forcings from eight Coupled Model Intercomparison Project Phase 5 climate models under four representative concentration pathways, to drive a newly developed land surface hydrological model to simulate streamflow, and analyzed historical and future hydrological drought characteristics based on the standardized streamflow index. The Wudinghe watershed will reach the 1.5, 2 and 3 degrees C warming levels around 2015-2034, 2032-2051 and 2060-2079, with an increase in precipitation of 8 %, 9% and 18% and runoff of 27 %, 19% and 44 %, and a drop in hydrological drought frequency of 11 %, 26% and 23% as compared to the baseline period (1986-2005). However, the drought severity will rise dramatically by 184 %, 116% and 184 %, which is mainly caused by the increased variability in precipitation and evapotranspiration. The climate models and the land surface hydrological model contribute to more than 80% of total uncertainties in the future projection of precipitation and hydrological droughts. This study suggests that different aspects of hydrological droughts should be carefully investigated when assessing the impact of 1.5, 2 and 3 degrees C global warming.