Urban Pollutant Plumes around Wushan and Dachang City in the Three Gorges Reservoir

Abstract

The Three Gorges Reservoir (TGR) in the Yangtze River was among other reasons meant to improve and strengthen socio-economic development of the involved regions. Considerable economic growth and urbanization now pose additional threat to the water quality of the TGR due to urban pollutant inflows. The changed hydrological conditions in the TGR have considerably altered pollutant transport dynamics now causing higher susceptibility of the backwater areas to eutrophication and algal blooms. The Yangtze River is also widely used as a source for drinking water production. The assessment of the urban impact on the water quality in the TGR is, thus, crucial for sustainable future development planning. Measurements with an underwater multi-sensor system (MINIBAT) were performed in the frame of the “Yangtze-Project” [1] around the cities of Wushan and Dachang on the Daning River in the backwater reaches of the TGR in December 2012. Hydrological conditions were stable at constant water level between 174–175 m.a.s.l and low discharge conditions in the TGR during sampling period. 3D distribution patterns of the parameters temperature, conductivity, and turbidity in the water bodies were modeled using geostatistics. Selected water samples from different depths were analyzed for dissolved and particulate constituents using ICP-MS. Results show plumes of higher temperature, conductivity and turbidity in the epilimnion around the investigated urban areas. The range of influence was larger for temperature and conductivity plumes. Significant increase of turbidity was detected around Dachang City during few hours. Urban impacts on the water quality were significant at the encountered conditions and need to be further investigated for risk assessment, especially concerning drinking water production and eutrophication problems.