State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, China.
PLoS One. 2021 Dec 1;16(12):e0260527. doi: 10.1371/journal.pone.0260527. eCollection 2021.
It is known that channel engineering, including the construction of piers, will change the river hydrodynamic characteristics, which is a significant factor affecting the transport process of pollutants. With this regard, this study uses the well-validated and tested hydrodynamic module and transport module of MIKE 21 to simulate the hydrodynamics and water quality under various pier densities in the Wuhan reach. Hydrodynamic changes around the piers show spatial differences, which are similar under different discharges. The range and amplitude of hydrodynamic spatial variations increase with the increase in pier density. However, there is a critical value of 1.25 to 2.5 units/km. When the pier density is less than this critical value, this type of cumulative effect is the most significant. Additionally, greater changes can be found in chemical oxygen demand concentrations, which also show spatial and temporal variations. The area with high chemical oxygen demand concentration upstream and downstream from the engineering area exhibits the distribution characteristics of "decrease in the downstream area and increase in the upstream area" and "increase in downstream the area and decrease in the upstream area" respectively. In the reach section of the engineering area, the area with high chemical oxygen demand concentration increases in the front area near the piers and decreases near the shoreline. Furthermore, the concentration shows attenuation actions with a longer residence time owing to the buffering effect of pier groups. These results have significant implications on shoreline planning and utilization. Moreover, they provide scientific guidelines for water management.
众所周知，航道整治工程（包括桥墩建设）会改变河流水动力特性，这是影响污染物输移过程的重要因素。有鉴于此，本研究采用经过良好验证和测试的 MIKE 21 水动力模块和输运模块，模拟武汉河段不同桥墩密度下的水动力和水质。桥墩周围的水动力变化具有空间差异，在不同流量下表现出相似的特征。水动力空间变化的范围和幅度随桥墩密度的增加而增大。然而，存在一个临界值为 1.25 至 2.5 个单位/公里。当桥墩密度小于该临界值时，这种累积效应最为显著。此外，化学需氧量浓度也会发生较大变化，且表现出时空变化。工程区上下游高化学需氧量浓度区域分别呈现“下游区减少、上游区增加”和“下游区增加、上游区减少”的分布特征。在工程区河段，桥墩附近前缘区域高化学需氧量浓度增加，而近岸区域则减少。此外，由于桥墩群的缓冲作用，浓度表现出衰减作用，停留时间更长。这些结果对岸线规划和利用具有重要意义，为水管理提供了科学指导。
