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| Titel |
Impact factors on water quality in the confluence zone of the Daning River and the Yangtze River at different hydrological conditions in the Three Gorges Reservoir |
| VerfasserIn |
A. Holbach, L. Wang, H. Chen, W. Hu, N. Schleicher, B. Zheng, S. Norra |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069339
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| Zusammenfassung |
| Water quality of the Three Gorges Reservoir (TGR) in the Yangtze River became a major
concern since the first closure of the dam in 2003. Increasing eutrophication and algal bloom
events, especially in confluence bays and backwater areas are observed. Substance transport,
water exchange and interaction between water masses in confluence areas of tributaries and
the Yangtze main stream are of special interest and mainly driven by large scale water level
fluctuations and temporal discharge variations in the reservoir. The Daning River, one
tributary of the TGR also adjoins to Dachang city and Wushan city which are by backwater of
the TGR.
In the frame of the Sino-German “Yangtze-Project” [1] water quality data and samples were
collected in the Daning River and its confluence zone with the Yangtze River during two
fieldtrips in August and December, 2011. Remarkable hydrological changes during the
sampling time were present in August whereas conditions in December were rather
stable.
Water quality data was recorded in-situ and on-line in varying depths with a towed
underwater sensor system. The monitored data comprise seven important physico-chemical
water parameters (temperature, electrical conductivity, turbidity, dissolved oxygen, oxygen
saturation, pH, chlorophyll a) coupled with a 3D positioning system. Geostatistical evaluation
and interpolation of the physico-chemical water parameter data was conducted to
get 3D distribution models for the parameters in the water bodies. Selective water
samples for analysis of inorganic components (anions, cations, nutrients) in the
dissolved and particulate phases were taken from different depths by a free flow
sampler.
Results reveal that pollutant plumes in the water above the thermocline surround the urban
areas during the stable conditions of December. In August the degree of mixing of
Yangtze main stream water with the Daning River water was the main driving force
for the water chemistry. Contrarily, water quality was mainly controlled by the
development and the collapse of a separated temperature layered water body in
the confluence bay at Wushan. Main algal growth was limited to the confluence
areas in the vicinity of the cities during both sampling periods. Consequently, water
chemistry and water quality of the confluence zone are both strongly dependent on the
hydrological and seasonal weather conditions but are not necessarily related to each
other.
Future work will focus on this and other study areas in the TGR covering different seasonal
and hydrological conditions. Results will also be used as input data for the numerical
modeling in the Yangtze-Project [1]. Important knowledge for the understanding of long-term
pollutant dynamics and water quality tendency in the TGR and other reservoirs can be
achieved.
Acknowledgments
The Yangtze-Project is funded by the Federal Ministry of Education and Research (BMBF
grant no. 02WT1131) of Germany and the International Science and Technology Cooperation
Program of China (NO. 2007DFA90510).
Many thanks to the Environmental Monitoring Station in Wushan, Chongqing, China for
great administrative and infrastructural support.
References
[1] Bergmann A, et al. (2011) The Yangtze-Hydro Project: a Chinese–German environmental
program. Environmental Science and Pollution Research. Doi: 10.1007/s11356-011-0645-7 |
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