Application of uncertainty theory to prediction and assessment of water quality in Three-Gorge Reservoir

Two-dimensional stochastic model of complicated river water quality was established. This uncertainty model was effectively combined with the numerical calculation algorithm of finite element method and Monte Carlo method. The calculation production of water quality was assessed by applying probability distribution (Monte Carlo method) and fuzzy set theory. It is indicated that there exists the problem of bank pollution, especially near the effluent outlets; and upriver water quality has a significant impact on the whole Three-Gorge Reservoir; only 40% possibility can be obtained to make water quality meet Grade II of Surface Water Quality Standard (GB3838-2002). However, this possibility for bad water quality is also very small, only about 10% to meet Grade IV standard.