Page - 232 - in Book of Full Papers - Symposium Hydro Engineering

IMPACT OF UPPER YANGTZE CASCADE RESERVOIRS OPERATION ON THREE GORGES RESERVOIR IN IMPOUNDMENT PERIOD Gao Yulei Engineer of China Three Gorges Corporation, China. Wang Hai Professorate senior engineer of China Three Gorges Corporation, China. 1. INTRODUCTION The Yangtze River is the largest river of China, with a total length of 6300km and a total drainage area of 1.8 million km2. The Three Gorges Reservoir (TGR) is the key backbone project for controlling the Yangtze River and developing and utilizing the water resources of the Yangtze River. Its normal storage level is 175 m, flood control level is 145 m, flood control capacity is 22.15 billion m3, and utilizable capacity is 16.5 billion m3, having a huge regulation and storage capacity; the reservoir takes on flood control, power generation, navigation, and other comprehensive utilization tasks. According to the preliminary design diagram, TGR start to impound on October 1 each year and will impound water to 175m by the end of October or November. From January to April of the following year, the water supply dispatch was implemented for the middle and lower reaches to meet the needs of shipping, water supply and ecology. The impoundment of TGR is an important prerequisite for giving full play to its huge water supply benefits. At present, a large number of reservoirs with large storage capacity and good regulation capacity have been built or will be built in the upper reaches of the Yangtze River. According to the long-term planning, the total regulation capacity of TGR and the upstream controlled reservoirs will approach 100 billion m3 and the total flood control storage will be 50 billion m3. As the upstream reservoirs are gradually put into operation, the regulation of runoff by the cascade reservoirs will become more and more obvious. The regulation of water volume during the year can reach 1/4 of the average annual water discharge of Yichang Station. These cascaded reservoirs are concentrated in the annual water storage from August to October, reducing the amount of storage water in the Three Gorges Reservoir and increasing the risk of failure in water storage of TGR. In recent years, many scholars have carried out a large amount of research on staging design floods, the comprehensive utilization of the TGR during the storage period, water level and node control water level optimization, and analyzed the flood control risks brought by the optimization plan. Based on the long series of runoff data used in the preliminary design, the long runoff data of TGR from September to October was calculated by considering the impact of reservoir water 232