Study on the Water Quality Evolution in the Shiyang River Basin

The fuzzy mathematics integration method was used to evaluate the status of surface water quality.The result showed: the quality of the upriver water was fresh, belong to I type, and was suitable for various kinds of uses; The water in the middle reach was polluted and belong to V type; The water in the Hongya Reservoir was polluted seriously. Although through self-purification of the river and function of diluting, the pollution had already been alleviated to some extentand the water still belong to V type, just its jurisdiction of degree was slightly smaller than the middle reach. the reasons of the water pollution on the basis of probing into the course of surface water evolvement was analysed. The main reasons of water pollution were of the increases of pollutant emissions and the reduces of coming water from upriver.