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Extreme meteorological and hydrological events frequently occur in the changing environment. The Yangtze River and Yellow River are facing the risk of simultaneous dry events. This paper analyzes the practical problems encountered in the Yangtze River basin and Yellow River basin following the construction of the national water network in order to ensure water resources security in the Yellow River basin when these two rivers experience simultaneous dry events. Urgent key scientific problems that need to be addressed include simultaneous dry events of large-scale basins in the changing environment, water crisis formation, interbasin water transfer potential, water network formation and the water transfer mechanism of multi-line projects, water resources security assurance during extreme dry events. An overall research framework for addressing extreme dry events in the Yellow River basin under the layout of the water network is proposed. Key research directions are analyzed from five aspects, namely, occurrence patterns and spatial variation mechanisms of simultaneous dry events in the Yangtze River and the Yellow River; quantitative assessment of multi-link transmission and compound impact of water crisis risk; interbasin water transfer potential in extreme dry events, interbasin water allocation and refined regulation of multi-line water transfer projects; and improvement of the resilience of thebasin water resource system during extreme dry events. [ABSTRACT FROM AUTHOR]

Coarse sediment movement in rivers is one of the key factors in causing changes in channel characteristics. The duration of the 2012 flood in the Inner Mongolia Reach of the Yellow River (IMYR) was the longest and the peak discharge was the biggest since 1989. The aim of this study was to investigate the impact of the movement of coarse sediment during the 2012 flood on the riverbed of IMYR, a coarse sand reach. The wide valley reach of IMYR is bounded by the Bayangaole, Sanhuhekou and Toudaoguai gauging stations from upstream to downstream. The coarse sand in the channel is one of the most important factors impacting riverbed erosion and deposition. Using real observational data, we analyzed the water and sediment characteristics of IMYR during the 2012 flood. By calculating sediment discharge of the bed load and comparing the river bottom of the fixed sections during the flood, this paper assesses the effect of the movement of coarse sediment on the river bottom adjustment. The results show that, ① the coarse sediment was scoured in the upstream part of the IMYR and deposited downstream during the flood in 2012; ② the open area beneath the fixed low water level followed the rule of scouring during the flood rising period and deposition during the flood falling period; ③ the open area under the low water at Bayangaole and Sanhuhekou gauging station expanded by 19 m2 and 29 m2 respectively, while the same at Toudaoguai gauging station decreased by approximately 100 m2. Owing to the imbalance of coarse sediment ejection after the flood, the actual elevation of the riverbed bottom did not get lower, and the flood risk remains at a similar level. [ABSTRACT FROM AUTHOR]