水动力方法改善品清湖水质的可行性及优化方案

为提升潟湖水环境质量和水动力条件，改善因潮水动力弱、自然条件限制和频繁的人类活动对沿海潟湖脆弱生态环境的影响，文章以亚洲第二大潟湖品清湖为例，基于MIKE21非结构网格建立了品清湖及周边海域二维水动力模型，并在此基础上耦合构建水质模型。通过分析对比品清湖现状与17种改造工况间的水动力及水质的影响变化发现，拆除近岸或者离岸1/2防波堤（工况2和工况3）或同步拆除1/4沙舌和部分崩坎角（工况9）可在较低工程量下有效地改善品清湖水动力及水质，使品清湖的整体平均流速提升10.42%~32.25%，纳潮量增加1.68%~2.48%，水体更新时间缩短21.44%~23.13%，TN和TP浓度分别降低9.0%~10.7%、11.2%~13%；工况2、工况3和工况9各有优势，但不适合共同实施。研究结果不但可为低成本品清湖修复工程提供实施依据，也可为潟湖的水动力、水质改善提供模拟案例。

Feasibility and Optimization of Hydrodynamic Methods to Improve Water Quality in Pinqing Lake

In order to enhance the quality and hydrodynamic conditions of the lagoon water, and to improve the ecological environmental impacts on the coastal lagoon due to weak tidal hydrodynamics, natural conditions restriction and frequent human activities, the second largest lagoon in Asia, Pinqing Lake was studied using a hydrodynamic water quality model based on unstructured grids of the surrounding waters. To develop cost effective approaches for the ecological restoration and development of Pinqing Lake, the hydrodynamic and water quality impacts between the current situation of Pinqing Lake and the 17 modification conditions were analyzed. The results show that the removement of 50% of the breakwater near or offshore (Case 2 and Case 3) or 25% of the sand tongue and part of the crumbling angle (Case 9) can effectively improve the hydrodynamics and water quality of Pinqing Lake at relatively low cost, increase the overall flow rate and tidal volume by 10.42%~32.25% and 1.68%~2.48%, reduce the renewal time of the water body by 21.44%~23.13%, reduce TN and TP concentrations by 9.0%~10.7% and 11.2%~13%. Case 2, Case 3 and Case 9 have their own advantages, but they are not suitable for joint implementation. Therefore, the water dynamics and water quality of Pinqing Lake could be improved by the removement of 50% of the breakwater or by synchronizing the removement of 25% of the sand tongue and a portion of the avalanche angle, or a similar effect could be achieved by a permeable retrofit.