Key scientific issues of hydrological forecast in the headwater area of Yellow River

The hydrological forecast for the headwater area of Yellow River is of vital importance to the flood water resources utilization through optimal operation of cascade reservoirs over the Upper Yellow River such as Longyangxia and Liujiaxia, even to the prevention of flood and drought disasters for the entire Yellow River basin. However, the hydrological forecast in the source region is one of difficult problems in the current operational forecast of flood and discharge of Yellow River, due to the critical deficiency of ground-based rainfall observations and the lack of special hydrological model for high and cold mountain areas. This paper first reviewed the domestic and international related studies and then demonstrated the current status and technical level of hydrological forecast in the headwater area of Yellow River from three aspects including precipitation observation and precipitation forecast over ungauged areas with high altitudes, construction of hydrological model in cold regions and integration of meteorological and hydrological coupling forecast system, and meteorological genesis and formation mechanism of plateau precipitation occurrence. Subsequently, several key scientific issues existed in current hydrological operation forecast are systematically analyzed. Finally, it is suggested that the future studies of hydrological forecast in the headwater area of Yellow River focus on several important directions, such as the new-generation multi-source precipitation information fusion and assimilation, the development of specific hydrologic model for high and cold regions, the seamless ensemble forecast technique based on the meteorological and hydrological coupling, the analysis of multiple weather systems triggering heavy precipitation and continuous overcast rain.