Calculation and analysis of flood regulation of Three Gorges Reservoir under check flood conditions

The check flood standard of the power plant of the Three Gorges Project is lower than that of the dam, and when encountering a once-in-10 000-year flood with a 10% increase in the check flood of the dam, the power station is at a risk of being submerged.To guide flood control and scheduling of the reservoir, the operating conditions, methods and requirements of reservoir scheduling were systematically sorted out, some calculation schemes of check flood regulation were formulated according to the requirements of regulations and norms.The impacts of the typical flood, the starting water level, the discharge capacity, and the tailwater blocking elevation on the reservoir level and the tailwater level were systematically analyzed, and the necessity of the power plant units to participate in the discharge of flood water was demonstrated.The conclusions were obtained as follows: ① The 1982 typical flood is more unfavorable in the upstream regional typical floods, the 1998 typical flood is less favorable in the basin-wide typical floods, and the 1982 typical flood is more unfavorable overall.② When there is no need to take into account the compensatory scheduling of Chenglingji flood control, the highest reservoir level will rise slightly with the starting water level, and in case of basin-wide flooding, it is necessary to take into account the compensatory scheduling of the Chenglingji river section, and the starting water level has little effect on the highest reservoir level.③ The more facilities involved in flood discharge, the greater the discharge capacity, the lower the maximum reservoir level for flood control, but at the same time, the greater the maximum discharge flow, the higher the maximum water level downstream.④ From the point of dam safety, it is necessary for the power plant units to participate in flood relief, and try to control the reservoir capacity regulating flood level below check flood level 180.40 m without affecting the safety of the tailwater platform.⑤ In order to ensure that the power plant units can participate in flood discharge under the dam check flood conditions, without changing the dam discharge conditions or raising the reservoir water level, the tailwater platform is at risk of inundation and requires temporary water retention and blocking measures.