A Study On The Contaminant Model In The Chongqing Urban Section Of The Yangtze River

Eutrophication of water body is one of the major environmental problems faced by China, which has already reduced the limited water resource, and brought about great negative impacts on the public's living and the sustainable development of the social economy. The Three Gorges Project on the Yangtze River is the biggest hydropower project in the world, which has begun to hold water in 2003. It is expected to be accomplished in 2009 with the reservoir volume of 39.3 billion cubic metres, in which 22.15 billion is for flood control. This project would benefit the river transportation, flood control and hydropower. However, the form of the Three Gorges Reservoir on the Yangtze River (TGRYR) would change the hydrologic characteristics of the Yangtze River and its tributaries, such as greater river width and depth, decreased water flow velocity, etc. These would lower the potential for pollutant solubility and dissolved oxygen recovery of the TGRYR water body and thus reduce its self-purification capacity. Now, the concentrations of nutrient pollutant in TGRYR nearly reach the critical level for eutrophication. There exists the high potential for eutrophication outburst in estuary, shore area and confluent retard area of tributaries. Once it happened, it would lower the water quality, damage the ecosystem in related areas, and obstruct the social economy development in TGRYR and even the down stream area. The characteristic section of this study is the main urban section of Chongqing City (MUSCQ), which is the central area of Chongqing City, the biggest the city of TGRYR upstream, and discharged millions of pollutants in the reservoir due to the large population and high developing industry. The study on the pollutant model of this section would benefit the whole TGRYR in eutrophication studies on mechanism and outburst conditions, the assessment index system, and determination of prediction indexes. Furthermore, it could provide scientific basis for the control of eutrophication researches in similar conditions. The water quality of MUSCQ was adopted in this study by QUAL2E, a powerful comprehensive water quality software for rivers developed by Environmental Protection Agency of United States, which is characterized by its comprehension, multi-purposes. The results showed that this model can be well used in MUSCQ for water quality modelling and prediction, and has good perspective in TGRYR. However, deep researches on the revisions for much better adaptation are still needed.