Modelling the effects of thermal stratification on the oxygen budget of an impounded river
Modelling the effects of thermal stratification on the oxygen budget of an impounded river
复制标题
模拟热分层对蓄水河流氧气收支的影响
DOI：
10.1002/rra.1260
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发表时间：
2009
影响因子：
2.2
通讯作者：
Andreas Schöl
中科院分区：
文献类型：
--
作者：
A. Becker;V. Kirchesch;H. Baumert;H. Fischer;Andreas Schöl
萨尔河是一条蓄水严重的河流，平均流量为80 m3 s−1。萨尔河的德国河段，即下游90公里，从1977年至2000年逐渐被蓄水，导致平均水深增加了一倍（今天为4.2米）。在河流发展的同时，水污染大大减少，缓解了河流中的临界氧收支。如今，在夏季的低流量期间，氧气浓度仍可能低于4 mg O2 l−1，此时会发生氧气的热分层和深度梯度。2005年8月，在48小时内对温度、电导率、湍流和氧气水平进行了高分辨率测量。这些数据被用来开发和验证一个“准二维”，深度解析建模方法与确定性水质模型QSim。该模型包括流速和太阳辐射对热分层的影响的数学描述，而水层之间的交换依赖于热分层。连续测量的三个数据集与模型输出进行了比较。热分层显示日节律和纵向变化取决于太阳辐射，水深和流速。在一天的过程中，测量和模型输出显示最好的协议在晚上最强的分层。热分层对氧收支速率的模拟影响被量化，并表明大气再曝气的减少部分地被藻类产氧的增加所补偿。对于萨尔河，这里记录的氧浓度的高时空变异性具有重要的生态意义。版权所有© 2009约翰威利父子有限公司。
The River Saar is a heavily impounded river with an average discharge of 80 m3 s−1. The German reach of the River Saar, i.e. the lower 90km, was gradually impounded from 1977–2000, resulting in a doubled average water depth (today 4.2m). In parallel to river development, water pollution was decreased strongly, relieving the critical oxygen budget in the river. Nowadays, oxygen concentrations may still fall below 4 mg O2 l−1 during low‐flow periods in summer, when thermal stratification and depth gradients of oxygen occur. In August 2005, high‐resolution measurements of temperature, conductivity, turbulence, as well as oxygen‐levels were carried out over 48 hours. These data were used to develop and validate a ‘quasi‐two‐dimensional’, depth‐resolving modelling approach with the deterministic water quality model QSim. This model includes the mathematical description of the influence of flow velocity and solar radiation on thermal stratification, on which the exchange between water layers depends. Three data sets of continuous measurements were compared with the model outputs. Thermal stratification shows diurnal rhythms and longitudinal variability depending on solar radiation, water depth, and flow velocity. In the course of the day, measurements and model outputs showed best agreement during the strongest stratification in the evening. The modelled effects of thermal stratification on oxygen‐budget rates were quantified and showed that the reduction of atmospheric re‐aeration is partly compensated by an increase in algal oxygen production. For the River Saar, the high temporal and spatial variability of oxygen concentrations documented here is of major ecological significance. Copyright © 2009 John Wiley & Sons, Ltd.