The study of water environment and sedimentation regimes in the upper Three Gorges reservoir

Based on the hydrological data (1950-2009) and using statistical method, the new variations of water runoff and sediment transport in the upper parts of Yangtze River basin have been dealt with. By analyzing the double accumulation curve of annual water runoff and sediment transport at the main hydrological stations, compared with the average annual values, this paper pointed out that, except for a slight increase recorded at Beibei station, a slight decrease is recorded at other main stations in the upstream of the Yangtze River and its tributaries; in terms of the annual sediment transport, the decrement was about 44% at Pingshan station and the percentage was even about 93% at Yichang station; and Gaochang, Beibei, Wulong have a decrement of 61%, 73%, 95%, respectively. The study also indicated that the sediment retained by water conservancy engineering decreased the amount of sediment transport effectively, whereas, the constructions of engineering have influence on the increase of the sediment transport to a certain extent. Some eutrophication parameters were monitored on the field such as chlorophyll-a (Chl.a), total nitrogen (TN), total phosphorus (TP). The water body has nutritive conditions for eutrophication occurrence, and there are seasonal water blooms already in Xiangxi River. The results not only help to improve the water quality but also provide references for reasonable operation of the Three Gorges reservoir.