Theory and practice of basin-wide floodwater utilization: Typical implementing measures in China

Floodwater utilization (FU) helps alleviate water shortages in regions with uneven rainfall. This study focuses on basin-wide FU, considering diverse water infrastructure and the delicate balance between flood risks and water scarcity. FU measures including optimizing the flood limited water level (FLWL) of reservoirs, extending the use of flood detention areas, and compensatory use of channel capacities, were reviewed and exemplified by real-world applications in China. The proposed procedure for implementing FU involves assessing FU potential, selecting appropriate utilization methods, and conducting a comprehensive evaluation of the associated risks and benefits. Using the Nansi Lake basin in China, as a synthesis example, the current-level FU potential and FU rate are estimated to be 1.47 km³/yr and 65 %. This FU value exceeds the theoretical potential, indicating the severe crowding out of ecological water uses. Multi-stage FLWL through raising the post-flood FLWL from 34.20 m to 34.35 m could increase the reservoir (the upper Nansi Lake) ability to refill by 19.1 %. Appropriate control of the sluices of interconnected rivers could conserve up to 0.135 km³ of floodwater from a single flood event without increasing flood risk.