Current status and future tendency of lake eutrophication in China

Current trophic status and trend of Chinese freshwater lakes were investigated in this study. The results showed that all lakes studied were commonly undergoing the eutrophication process, water quality decreased and lake's ecosystem is being declined. Most of the urban lakes are facing serious eutrophication. Many medium-sized lakes are in metrophic or eutrophic status, some local water are even approaching the hypertrophic level. The famous five freshwater lakes in China have entered into eutrophication in the condition of higher nutrient load. Lake Taihu, Hongze and Caohu are already in eutrophic state. Eutrophic lakes are mainly distributed in the middle and lower reaches of Yangtze River and Yungui plateau. Lake eutrophication developed rapidly. Among the 34 lakes studied in 1970's, most of lakes were in the mesotrophic status, mesotrophic water area accounted for 91.8%. With the nine year of 1978-1987 the area percentage of oligotrophic lakes decreased from 3.2% to 0.53%, and that of eutrophic lakes increased from 5.0% to 55.01%. Recent data showed 57.5% lakes were in eutrophic and hypertrophic status of the 40 surveyed lakes. Eutrophic trend of Lake Taihu, Chaohu and Xuanwu in the region of the middle and lower reaches of Yangtze River was predicated using the ecological stress model. The results showed that in 2008 Lake Taihu, Chaohu and Xuanwu might be of eutrophication, eutrophication and hypertrophication, respectively if no control measurement is taken. Provided the pollution water treatment rate is 60% in 2030, approximately 30 billion ton pollution water would still be discharged directly in the lakes. Therefore, in 2030 the urban lakes in China might be eutrophication or hypertrophication, and most of the medium-sized lakes at the urban-rural fringe might be in eutrophication or hypertrophication. The famous five biggest freshwater lakes in China might be eutrophication if control countermeasures are taken as now. Lake eutrophication has become a serious environmental problem in China. Based on the domestic and foreign experiences of the eutrophic control technologies, both nutrient pollution control and lake ecological restoration should be carried out and this may be the guidance for the eutrophic control of lakes in China.