Holbach A, Bi Y, Yuan Y, Wang L, Zheng B, Norra S
Institute of Applied Geosciences, Karlsruhe Institute of Technology, Kaiserstraße 12, 76131 Karlsruhe, Germany.
Environ Sci Process Impacts. 2015 Sep;17(9):1641-53. doi: 10.1039/c5em00201j. Epub 2015 Jul 23.
Ecological consequences of large dams, particularly regarding the Three Gorges Dam (TGD) on the Yangtze River in China, have been controversially and internationally discussed. Water quality within the Three Gorges Reservoir (TGR) has been deteriorated by highly underestimated eutrophication and algal blooms. Globally, the TGR is delineated from other comparable reservoirs by its low mean water residence time and its 30 m annual water level fluctuation. We used an in situ and online multi-sensor system 'MINIBAT' to analyse eight indicative physico-chemical parameters across depth and time within the Xiangxi River backwater, a representative major tributary of the TGR. The results revealed considerably changing environmental water body characteristics within the tributary backwater related to the TGR's typical seasonal hydrology. The Yangtze River main stream appeared to be the major contributor of dissolved and particulate water constituents within the Xiangxi River backwater. Eutrophication problems in spring and summer seasons are likely a consequence of extensive water mass exchange and pollutant transport processes in autumn and winter. In particular, the backwater's permanently stratified water column shows varying layered impacts of the Yangtze River main stream and Xiangxi River headwaters. This is a clear indication of a complex stratified flow pattern within this TGR tributary backwater. In our study, a major driver for the Yangtze River main stream impact was the rising TGR water level. The TGR's globally unique characteristics have thus become a central part of the recent eutrophication and pollution problem within the TGR. Thereof, we deduced a proposal for an adapted dam management strategy.
大型水坝的生态后果，尤其是中国长江上的三峡大坝，在国际上一直存在争议并被广泛讨论。三峡水库内的水质因富营养化和藻类大量繁殖被严重低估而恶化。在全球范围内，三峡水库因其较低的平均水停留时间和每年30米的水位波动而与其他类似水库有所不同。我们使用了一个原位在线多传感器系统“MINIBAT”，对三峡水库代表性主要支流香溪河回水区域内不同深度和时间的八个指示性物理化学参数进行了分析。结果显示，该支流回水区域内的环境水体特征随三峡水库典型的季节性水文情况发生了显著变化。长江主流似乎是香溪河回水区域内溶解态和颗粒态水体成分的主要来源。春夏季的富营养化问题可能是秋冬季节广泛的水体交换和污染物传输过程导致的。特别是，回水区域永久性分层的水柱显示出长江主流和香溪河源头不同的分层影响。这清楚地表明了三峡水库该支流回水区域内存在复杂的分层水流模式。在我们的研究中，长江主流产生影响的一个主要驱动因素是三峡水库水位上升。因此，三峡水库全球独有的特征已成为近期三峡水库富营养化和污染问题的核心部分。据此，我们推导了一项适应性大坝管理策略的建议。
