Research On The Contribution Of Lateral Inflow To Floods In Three Gorges Reservoir

Floods occur frequently in the Yangtze River Basin. The Three Gorges Dam playsan important role in flood prevention of Yangtze River, and an efficient floodforecasting system will be helpful to give full play to its flood prevention benefit.However, flood forecasting of the lateral inflow of Three Gorges Reservoir (TGR),which offers mostly of the uncertainty, has3characteristics: high contribution to floodsin TGR; lack of observation; short confluence time. In this paper, the accuracy of theIntegrated Forecasting and Modeling System in TGR (Hydro-InForMS) is tested, andthe quantitative analysis of the contributions of the lateral inflow to floods in TGR isconducted. Meanwhile, the frequency analysis of the lateral inflow is completed, basedon which the investigation of lateral inflow encountered with upstream inflow isconducted.Hydro-InForMS is a coupled hydrologic-hydraulic system based on rain data fromvarious sources to forecast the inflow, floods within TGR, and both water level anddischarge at the dam site. The test results of the floods in2010to2013, simulated byHydro-InForMS, refers that the average determinacy coefficients (DC) of simulatedinflow, discharge at the dam site, water level of gauges along main channel are0.94,0.91and above0.99respectively. And the average absolute error of simulated waterlevel peak at the dam site is0.29m. In general, Hydro-InForMS simulates well.The quantitative analysis of the contribution of lateral inflow to floods in TGR isconducted based on Hydro-InForMS. It shows that the highest contribution ratio oflateral inflow to peak of the inflow and discharge at the dam site is53.7%and47.9%respectively. The contribution of the lateral inflow to peak of the inflow and dischargeat the dam site reaches highest in June, and it decreases when time passes. The averagecontribution of the lateral inflow to the submerge line could be up to1.05m. In general,the lateral inflow contributes a lot.The frequency analysis of the simulated lateral inflow (1961to2011) based on raindata, observed by meteorological stations, is conducted. Biult on the analysis results, theencounter pattern between lateral and upstream inflow is scenario simulated by MIKE11, and the dangerous one is found. Under the dangerous encounter pattern, the estimate of dam-site water level process caused by lateral inflow on various frequencies isoffered. Then, as the estimate process has been proved that could be applicated inhistorical flood, it has been proved a valuable reference to reservoir options underdangerous encounter patterns.