A hydrological perspective on drought risk-assessment in the Yellow River Basin under future anthropogenic activities

Since the late 1970s, the Yellow River Basin (YRB) has experienced accelerated land-use/land cover changes (LULCC) and consumptive water use (CWU) that have imposed low-flow regimes. Upon the continuation of these anthropogenic activities in the future, significant hydrological alteration is expected. This study takes a hydrological perspective on drought to project changes in the YRB drought risk under future LULCC and CWU business-as-usual (BAU) scenarios. A combination of seasonal trend forecasting, drought indices, land-use and hydrological modeling techniques was used. Future LULCC is assessed based on two BAU scenarios to explore the patterns of LULCC with (LULCC-BAU1) and without (LULCC-BAU2) the continuation of the Chinese Grain for Green Program. The results indicated that LULCC-BAU2 will increase the risk of mild and moderate droughts, while CWU and LULCC-BAU1 will impose higher risk of severe and extreme events. LULCC-BAU1 is projected to exacerbate the duration and intensity of the agricultural/hydrological droughts. The frequency of hydrological drought under LULCC-BAU1 and CWU scenarios is projected to increase by 43% and 53% during 2021-2050. The future agricultural droughts will likely be more intense and prolonged than meteorological droughts. Hydrological droughts, however, will be characterized by prolonged but less intense drought comparing to the metrological droughts. The meteorological to agricultural drought propagation will likely be driven by LULCC under BAU1, while the meteorological to hydrological drought propagation is controlled by CWU changes.