Page - 238 - in Book of Full Papers - Symposium Hydro Engineering

4.3 THE INFLUENCE OF RAISING INITIAL IMPOUNDING WATER LEVEL ON THE DISCHARGE OF TGR DURING IMPOUNDMENT PERIOD. According to the present situation of scheduling rules, TGR began to impound from September 10th. compared with the 145m water level, if the initial water level of TGR is raised up to 148m, 150m, 152m and 155m respectively,the average discharge can be increased by 350m3/s, 590m3/s, 860m3/s and 1310m3/s during the impoundment period.Since 2010, TGR has been reached to the normal water level of 175m for 8 consecutive years of water.Except for the serious water shortage in early September and low water storage level in 2016, the TGR initial storage level of other years were above 152m.The discharge of TGR during the impoundment period was raised, effectively alleviating the contradiction between reservoir water storage and downstream water use. 5. CONCLUSION After the operation of the upstream large reservoirs, the runoff of Three Gorges Dam from September to October is 9.7billion m3 and 22.2 billion m3 less than that of the initial design value respectively, which has a great impact on the impoundment of TGR.In the 2017 level year, that is the status quo year, it is reasonable for TGR to start impounding on September 10 based on the current joint storage of cascade reservoirs in the basin. But the initial water level should be raised to the increase the discharge during the impoundment period.In the prospective level year, due to the large storage capacity of new large reservoirs,the impounding time of TGR will need to be arranged on September 1 in advance,in order to reach the designed full storage rate . The contradiction between the centralized storage and downstream water supply will be further exacerbated after the operation of the constructed and proposed reservoirs in the upper reaches of the Yangtze River .Therefore, the water storage scheme of TGR needs to be optimized continuously.In general, the impounding time of upstream reservoir is earlier than that of TGR. Therefore in the preparation of the annual impounding scheme of TGR, raising up the reservoir initial water level under the premise of ensuring the safety of flood control according to the real-time progress and inflow forecast.The full storage rate of TGR could be increased and the contradiction between reservoir water storage and water supply in the downstream area will be relieved. 6. ACKNOWLEDGEMENTS 238