Water Quality Assessment And Modeling Of Rivers And Lakes Along The Yangtze River

Water quality is very significant to sustainable social-economic development of economics zone of the Yangtze River. The object of the study is to assess and model water quality with major parameters (e.g. DO, BOD, COD, NH₃-N, NO₃-N, TN, PO₄^3-) using some new methods (e.g. Logistic Regression, Hydrologic Process Modeling in.GIS) on the base of full-scale collection of water quality data for the Yangtze River, to serve for water quality management and control of the Yangtze River Basin. Ultimately over 100,000 monitoring data of 540 hydrometrical stations in the Yangtze River system from 1958 to 1990 and over 2,000 month or year averages of 20 local rivers (and lakes) in 10 cities along the Yangtze River from 1990 to 1996 were collected.The study includes four parts: 1) Assessment of water quality of mainstream, major tributaries, and lakes along the Yangtze River (regional distribution, seasonal variance, and evolution trends during 1960s to 1990s of water quality parameters (oxygen-equilibrium parameters and nutrients parameters), 2) Assessment of water quality of local rivers or lakes of 10 cities (Shanghai, Nantong, Wuxi, Changzhou, Nanjing, Hefei, Jiujiang, Wuhan, Yichang, Chongqing) along the Yangtze River, 3) The spatial distribution of oxygen-equilibrium parameters and nutrients of the Yangtze River Basin and the relationship between which and regional nature conditions and social-economic development, 4) Non-point source modeling of water quality of the Yangtze River Basin using GIRD module in ARC/INFO, the contribution of non-point source contamination to the Yangtze River system.The main conclusions are as follows:1. Water quality of mainstream of the Yangtze River is still good; Water quality of upper reaches of the mainstream is better than that of lower reaches; There exists river-shore contaminated zone near the cities along the mainstream which located especially in Chongqing, Wuhan, Nanjing, and Shanghai Reaches.2. Of the major tributaries of the Yangtze River, the Great Cannal, the Huangpu River, and the Tuo River are polluted seriously while the others are better.3. Of the big lakes along the Yangtze River, eutrophications of Chao Lake and Tai Lake are heavy; Water quality of Dongting Lake and Poyang Lake is basically good, but there exists eutrophical trends.4. Almost all local rivers and lakes of 10 cities along the Yangtze River are polluted or polluted heavily, of which the pollution levels are related well with population, development, and pollution discharge loads of cities.5. In polluted slightly reaches of the rivers, water quality in dry seasons is significantly better than that in the flood seasons. This phenomenon perhaps is related to the non-point source pollution in the flood period. In polluted heavily reaches of the rivers, water quality in dry season is significantly worse than that in the flood seasons. This phenomenon perhaps is related to powerful dilution to point pollution in the flood period. Because of complex influence of the two...