Application Of SMS Model For Water Quality Simulating And Predicting In Zhengjiang Neijiang

Facing with river water environment around the world getting worse and worse, hydrodynamics and water quality modeling technique, which is an important means for understanding the status and trends of river environment, has been extensively applied in the protection and management of river water environment. How to improve the water quality of Zhenjiang Neijiang is one of important issue in environmental improvement,repairing technique and synthetically demonstrating in Zhenjiang water environment in "The tenth five years' plan". In order to evaluate and analysis efficiently the water quality status of Neijiang, it will be some theoretics meaning and practical value to establish Zhenjiang Neijiang water quality model.The paper expounds the structures and functions of RMA2 and RMA4 which are two-dimensional depth-average finite element numerical models endorsed by the USACE-Engineering Research and Development Center (ERDC) at the Waterways Experiment Station (WES) as well as the Federal Highway Administration (FHWA). The author uses the equivalent criterion pollutant index method to evaluate water quality based on the analyzing on the current condition in Zhenjiang Neijiang. It concludes that the organic pollution is the main pollution, and the quality of low water can't reach the criterion. RMA2 is applied to do the hydrodynamic analogy of the Neijiang. The relative errors of water level and velocity of flow validated points are less than 10%. And the outcome indicates that the simulation can be near to the actual condition, reflecting truly the hydrodynamic condition of Neijiang. With the results of RMA2, water quality simulation is operated with BOD₅,COD_mn NH₃-N TP as the contaminative factors. The range of the contaminative factors is: during the low water, the concentration of BOD₅ is 3.2～8.8mg/L, COD_Mn is 4.7～6.8mg/L, NH₃-N is 0.46～1.8mg/L, TP is 0.23～0.48mg/L; during the high water, BOD₅ is 0.69～0.73mg/L, COD_mn is 1.9～2.3mg/L, NH₃-N is 0.25～0.38mg/L, TP is 0.14～0.17mg/L; The values are close to the actual values. The simulation outcome shows that the pollution is more serious in low water period, and the concentration of contaminative factors are higher than V kind of surface water quality standard. In addition, Water environment capacity of Zhenjiang Neijiang is computed using complete-mix-system water environment capacity calculation formula. In low water period, the quantity of BOD5 that should be cut down is 19.3t/d, and the quantity of NH₃-N is 5.9t/d. These provide referenced foundation for water pollution renovating of Zhenjiang Neijiang.So, it is important to improve Neijiang water quality in low water period. The paper suggests that we can use surface fountain pollutant controlling measures and Neijiang water body's self cleaning capability to improve water quality status. It can simulate water quality of improved Neijiang, and compare the outcome with current status, which are scientific bases for establishing Neijiang water environment protection methods. Under the measure of surface fountain, the concentration of BOD₅ and COD_Mn reduce 10%～20%, and the concentration of NH₃-N and TP reduce over 50%. Under the methods of improving Neijiang self cleaning capability, the concentration of BOD₅,COD_mn,NH₃-N and TP respectively reduce 10%～20%.