Risk analysis for reservoir flood control operation considering two-dimensional uncertainties based on Bayesian network

Floodwater conservation in reservoir flood control capacity will lead to additional flood control risk for reservoir operation during flood seasons. Coupling the meteorological and hydrological uncertainties, the probability density function of reservoir initial flood regulation water level is derived to quantify the uncertainty in floodwater conservation through an analytical method. In reservoir flood control operation, the uncertainty of initial water level being above the designed flood limited water level and the uncertainty of inflow caused by flood forecast error are two main risk factors. This study developed a dynamic and intelligent risk prediction and diagnosis model for reservoir flood regulation under two-dimensional uncertainties based on Bayesian network. Three modules are included: Bayesian network structure learning, parameter learning, and probability inference. The nodes of Bayesian network are determined and the network structure is established with expert knowledge; the parameter learning is conducted with the training samples obtained from Monte Carlo simulation. Thereafter, through the prior probability inference without posterior information and the posterior probability inference with given posterior information, the variation of flood risk is analyzed under single-factor uncertainty and two-factors uncertainties. The model is applied to Xianghongdian Reservoir in China using a flood of 100 years return period. Results indicate: the risk resulted from inflow uncertainty is greater than that of the uncertainty of initial water level; there is a certain complementarity between the uncertainties of inflow and initial water level, and the combined risk is between the results of two single-factor risk levels. Moreover, Bayesian Network is able to conduct bi-directional inferences and infer the probability distribution of any other node, which has practical value for risk assessment and control of reservoir flood control operation.