Pollution Load Analysis In Small Urban Basin

As the rapid development goes on, the environmental problems, especially the water quality problems, become more and more severe. As the leading city in the western exploiting, Xi'an pays more and more attention on the environmental problems. The Zao he that flows through the downtown district of Xi'an has become seriously polluted. The worsening water environmental quality affects the sustainable development of the city.Base on the character of small urban basin ,considering the natural hydrological characteristic and the social factors that affect the water quality, and the meteorologic data in the Zaohe basin, water quality model combined three-level water tank model, kinetic wave model and one dimensional river water quality model has been finally constructed.With the application of GIS, the main factors that affect water quality, including climate, hydrology, soil character, land usage, population, economical development, and distribution of polluting sources, the river basin boundary has been confined.With considering the natural cycle of precipitation, evaporation and runoff, and inducting industrial, agricultural and domestic water supply and drainage quantity, three-layer water tank model has been adopted to calculate the river afflux quantity and pollutant discharge amount. And with the use of kinetic wave model, the river flow amount has been calculated. Ultimately, combined with the one dimensional diffusion equation, the regularity of the main water quality indices such as SS,BOD₅,DO,NH₄ ⁺-N,NO₃ˉN have been calculated. Use the monitoring data to check the model and according to the model export to analyse the rule of Zaohe runoff and water quality then control the pollution of Zaohe in proper measurement.