半封闭湖泊水体交换能力模拟及提升措施研究：以海棠湾龙江塘为例

Study on simulation and improvement measures of water exchange capacity in semi-enclosed lakes: A case study of Longjiang Pond in Haitang Bay

摘要

【目的】半封闭湖泊的水体交换主要依赖于入湖河流，容易出现季节性、潮汐性缺水问题。在气候变化和人类活动的双重影响下，半封闭湖泊缺水问题日渐突出，进而引发水质恶化、生态退化等复杂问题，亟待通过有效方式加以改善。【方法】选取龙江塘作为研究对象，建立龙江塘二维水动力-水质数学模型，选取污染物相对浓度和水体半交换时间作为评价指标，对比了现状和水系连通工程建成后龙江塘内水体交换能力。【结果】结果表明：现状条件下，龙江塘污染物相对浓度和水体半交换时间均表现为从南向北递增的趋势，北湖区污染物相对浓度下降最慢，水体半交换时间基本在2周以上；南湖区污染物相对浓度下降最快，水体半交换时间基本在1周以内。连通工程建成后，污染物相对浓度和水体半交换时间变为西部区域大于东部区域，北湖区污染物相对浓度下降速度加快，尤其是靠近1~#水系连通工程的东部区域，在计算第2天相对浓度降低至0.17;南湖区污染物相对浓度下降速度在前10天有所减缓，其中西部区域最为明显，水体半交换时间由6 d延长至14 d,在第20天后污染物相对浓度降低至0.2以内。【结论】研究表明：水系连通工程有助于加速半封闭湖泊污染物相对浓度下降速度，并有效缩短水体半交换时间，但会削弱原连接通道附近的水动力条件，本研究可为改善类似半封闭湖泊的水环境提供参考。

Abstract

[Objective] Water exchange in semi-enclosed lakes mainly relies on river inflows, making it prone to seasonal and tidal water shortages. Under the combined influence of climate change and human activities, the issue of water scarcity in these lakes has become increasingly prominent, leading to complex problems such as water quality deterioration and ecological degradation, urgently requiring effective solutions. [Methods] Longjiang Pond was selected as the study area, and a two-dimensional hydrodynamic-water quality mathematical model of Longjiang Pond was established. Relative pollutant concentration and half time of water exchange were taken as evaluation indicators to compare the water exchange capacity of Longjiang Pond before and after the completion of the water system connectivity project. [Results] The result showed that under current conditions, both relative pollutant concentration and half time of water exchange in Longjiang Pond exhibited an increasing trend from south to north. In the northern lake area, the pollutant concentration decreased the slowest, with the half time of water exchange generally exceeding 2 weeks. In contrast, the southern lake area experienced the fastest decline in pollutant concentration, with the half time of water exchange generally within one week. After the implementation of the water system connectivity project, both the relative pollutant concentration and the half time of water exchange became higher in the western region than in the eastern region. The pollutant concentration in the northern lake area declined more rapidly, especially in the eastern region near Water System Connectivity Project No. 1, where the relative concentration decreased to 0.17 on the second day of simulation. In the southern lake area, the decline in pollutant concentration slowed during the first 10 days, especially in the western area, where the half time of water exchange increased from 6 to 14 days. After 20 days, the relative pollutant concentration decreased to below 0.2. [Conclusion] The findings demonstrate that the water system connectivity project helps accelerate the reduction in relative pollutant concentration and effectively shorten the half time of water exchange in semi-enclosed lakes. However, it weakens the hydrodynamic conditions near the original connecting channels. These findings can provide a practical reference for improving the water environment of similar semi-enclosed lakes.

关键词

半封闭湖泊 / 水体交换能力 / 水系连通工程 / 数值模拟 / 污染物相对浓度 / 水体半交换时间

Key words

semi-enclosed lake / water exchange capacity / water system connectivity project / numerical simulation / relative pollutant concentration / half time of water exchange

基金资助

国家重点研发计划(2023YFC3208500)

南京水科院基本科研业务费项目(Y223002)