Dynamic Application and Risk Analysis of Flood Control Water Level to the Three Gorges Reservoir by Utilizing Mid-Term Inflow Forecasts

The objective of this study is to carry out reliability and risk analyses of a methodology of dynamically applying Flood Control Level (FCL) within a constraint boundary for the Three Gorges Reservoir (TGR) in middle China. The dynamic application model is based on the mid-term inflow forecasts, with different dispatching rules developed for forthcoming inflows of different magnitudes. The reliability analyses of applying this model were conducted by simulating the model by forecasted inflows of 6 extreme flooding years. For the lack of real forecasting data, the so-called forecasted inflows were actually artificially generated by a stochastic model. The risks of applying such a dynamic application model were calculated by generating 9 999 design floods, for segmented 3 flooding stages in a flooding season, and for varying return periods. The obtained design floods were then routed through the dynamic application model, the exceedance frequencies of the results which violating the defined 3 risk events were calculated, and regarded as the risk rates. The results showed that the forecast-based dynamic application model is reliable for at least the routed 6 extreme years, therefore assumed to be also reliable for other normal hydrological years. The calculated risks of applying such a model are also much smaller compared to a research result accomplished previously. Therefore, both reliability and risk analyses indicate the applicability of the developed model under variational FLC conditions for the TGR.