Study On Numerical Simulation And Risk Assessment Of Water Pollution Scenarios In Three Gorges Reservior

Study on numerical simulation and risk assessment of water pollution accident is essential to the water safety and emergency management, for communities and industries along the banks of Three Gorges Reservoir in China. In this paper, the pollutants evolvement with time as well as the recovery process with emergency actions under accidental pollution scenarios were studied and illustrated numerically, followed by the development and application of dynamic risk assessment model based on numerical simulation for Three Gorges Reservoir.Main research content is as follows.Dynamic characteristic of fluid was studied by a flow model coupled with the topography which was generated based on measured boundary and bathymetry data. Numerically simulated flow velocity was compared with measured data at selected sections to verify the modeling.Experimental study of the water recovery and safety was carried out in a freshwater creek which was polluted by a heavy fuel oil spill. Spatial difference of oil residues and the changes over time of water sampled in the creek were discussed to understand the pollutants degradation and toxic chemicals leaching with time.Oil fractions evolvement with time as well as the recovery process with emergency actions under oil spill scenarios were numerically simulated and illustrated in the reservoir, based on an oil spill model coupled with the hydrodynamic module under slow, quasi-static and supercritical flow separately. Three different forms of oil fractions, floating oil, sticking oil and dispersed oil, were presented to describe the simulated results. Emergency actions were accordingly analyzed based on the simulated pollution area and density, by which a decay parameter was additionally brought into the simulation to understand the recovery of polluted area and the effectiveness of emergency actions.Pollutants transport and fate of E.Coli and toxic chemicals under accidental spill scenarios with emergency actions in the reservoir were numerically simulated and illustrated separately by coupling a water quality model with the hydrodynamic module, based on the investigated hazards along river banks. Decay process and recovery of polluted water was simulated and analyzed by adding emergency actions to the pollution area, to study and understand the pollution evolvement of E.Coli and toxic chemicals spill accidents in the reservoir.Dynamic risk assessment of accidental spill scenarios was developed based on individual event valuing with real time numerical simulated results. Novel calculating methods combine Master Logic Diagram to identify the contributing events, Analytic Hierarchy Process for weight calculating and fuzzy clustering for risk grading. The model was then applied to the risk assessment of an oil spill scenario under quasi-static fluid with and without emergency action separately, an E.Coli pollution accident with flood and an accidental chromium discharging under supercritical fluid.