Study on the coordinating strategy of the Three Gorges Reservoir for ecological operation to promote spawning of the four major Chinese carps and comprehensive utilization demand

Abstract

[Objective] The coordination strategy between ecological operations of the Three Gorges Reservoir(TGR) to promote the natural spawning of the Four Major Chinese Carps and other comprehensive utilization demands has yet to be clearly defined. To clarify the constraints of ecological operations and propose coordination strategies between ecological operations and other comprehensive utilization demands, [Methods] past ecological operation experiments, operation regulations and operation practice of the TGR are summarized. Additionally, the impacts of conducting ecological operations during the concentrated falling stage and the flood stage on other comprehensive utilization demands have been quantitatively analyzed. [Results] The result show that, ecological operations during the per-flood falling stage will result in water abandonment at Gezhouba Dam in 47.3% of years and water level daily decrease of the TGR exceeding 1 m in 47.3% of the years. The risk of water abandonment at Gezhouba Dam and water level daily decrease of the TGR exceeding 1 meter will be significantly mitigated by raising the water level of the TGR on June 10th or lowering it on May 25th. Water demand of the ecological operations in mid-June and late June during flood stage can not be satisfied under the typical year of P=90%. [Conclusion] Conclusion can be drawn as follows: if ecological operations were conducted during the pre-flood falling stage, there would be no constraints on water quantity and no impact on flood control, water supply, and navigation. However, there would be risks associated with water abandonment at Gezhouba Dam and water level daily decrease of the TGR exceeding 1 m. Conducting ecological operation during flood stage is mainly subject to water constraints, while flood control risks remain manageable. Considering ecological operations, optimal operational rules for the TGR can be formulated as follows: in years with relatively abundant inflow forecasts, the reservoir level can be preemptively lowered the water level by May 25th. Conversely, the water level on June 10th can be further raised to 150.0 m in years with deficient inflow forecasts.

Keywords

Three Gorges Reservoir / four major Chinese carps / ecological operation / comprehensive utilization demand / coordination analysis / influence factor