Temporal-spatial evolution of water quality in Lake Dongting,China

According to Basic Analytical Methods of Environmental Quality Standards for surface water,GB3838- 2002,we used the 1983-2004 monitoring data to evaluate and characterize water quality condition and to analyze water quality temporal-spatial evolution trend of Lake Dongting,based on the application of comprehensive index methods such as Nemerow Index.The results showed that Water quality changed in Lake Dongting which fluctuated between up and down temporally.In 1983-1985,water quality was clean in Lake Dongting.From then on,water quality had been polluted seriously in 1988 and graduated in light pollution after 1991,and then ran down in 1999 and dropped to light pollution in 2001 again,as well as had begun to aggravate in 2004.The main pollutant was to- tal phosphorus(TP)in Lake Dongting.Water quality was worse in the flood water season than in the other water seasons,but after 2002,water quality in the flood water season had been better than in the normal water season. The water pollution could be more serious in the entering riverways than in the lake bodies of Lake Dongting spatial- ly.Water quality in lake West Dongting was worst,in Lake South Dongting was worse,and in Lake East Dongting was not polluted badly.