Variations in pollutant fluxes of rivers surrounding Taihu Lake in Zhejiang Province in 2008

The objective of this research was to estimate pollutant fluxes of rivers in Zhejiang Province as part of Taihu Lake Basin for better water quality management. Based on the water flow and water quality data of these rivers during the year of 2008, the temporal and spatial variations of water flow and water quality were analyzed. The results showed that the water quality of the rivers remained stable. The water quality parameters such as ammonia nitrogen (NH3–N), COD and total phosphorus (TP) in most of the monitoring sites met National water quality standards (National Grade III). The water flow of the rivers was greatly influenced by rainfall events of Taihu Lake. The influent flow of the lake was less than that of effluent flow prior to 2008; and an opposite trend was observed in 2008 because of more rainfall events. Based on the water flow and water quality data of the rivers, the pollutant fluxes were estimated. The results showed that the flux of COD, NH3–N, total nitrogen (TN) and TP into the lake was 10,472, 1109, 4461 and 314 t/yr respectively, while the respective flux out of the lake was 10,285, 421, 2383 and 226 t/yr. The pollutant netflux from the highest to the lowest was: TN > NH3–N > CODMn > TP. According to the spatial distribution of the pollutant fluxes, Tiaoxi Watershed contributed the most to the pollutant influxes into the lake. Attention should also be paid to the rivers in Changxing County, which accounted for about 30% of the pollutant load of the entire region.