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The main purpose of this study is to develop a water quality simulation model of river in order to aid the decision maker in water quality simulation of strategies planning of water pollution control. Moreover, this study also identify various water quality impact of point and nonpoint sources on river by the use of the water quality simulation model. The pollution sources considered includes point and nonpoint sources in the water quality simulation model. The component of river basin system considered includes branches, tributaries, tidal and non- tidal areas. The river system is assumed to be an one dimensional steady state system. The water quality parameters are simulated includes DO, BOD, T-N, and T-P with an assumption of first order decay of BOD,T-N and T-P. What are to be discussed in the case study of Chung-Gung River results have shown that : (1)it is required to consider nonpoint sources in the planning of water quality control strategy; (2)the loading of point source is fixed, the water quality impact will be added when the non-point sources discharge into the river. The water quality impact will become larger when the loading is larger; (3)the loading of point source is more larger then the water quality impact of varies loadings of nonpoint sources is vary small. But the water quality impact of nonpoint sources will be vary large when the loading of point source is small. So that the control of nonpoint sources is becoming a major challenge to water quality manager when the most point source pollution have been controlled; (4)in general, the water quality impact of distributed discharges will be reduced, nonpoint sources almost get into the river with distributed discharge. However, this study consider the nonpoint sources as most sever, so that the real water quality of river seems to be much better than the simulation results; (5)at various base flow, the water quality impact of nonpoint sources on river will be reduced when base flow become lager.
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