不同来水条件下洞庭湖二维水动力水质模拟

Two-Dimensional Hydrodynamic Water Quality Simulation of Dongting Lake under Different Incoming Water Conditions

摘要: 为研究不同来水条件对洞庭湖水动力水质的影响，本文构建了洞庭湖二维水动力–水质耦合模型，通过改变模型水动力边界和水质边界过程，模拟并分析了江湖水量交换变化和入湖污染负荷变化下洞庭湖水动力水质的响应过程，研究结果表明：① 三峡运行后三口入湖水量、江湖连接处的水力特性发生变化，进而影响湖区水动力水质的时空分布情况，如10月份三峡进入蓄水期，入湖水量减少，湖区TP、TN浓度整体呈上升趋势，但由于长江干流来水减少，出湖口水力坡度加大，东洞庭湖站至出湖口区域的TN、TP浓度有明显的减少趋势；② 当保持基准年入湖流量过程不变，使入湖污染负荷量整体减少10%时，西洞庭湖北部、南洞庭湖南部区域TP、TN浓度下降幅度较明显，东洞庭湖站6、7月份，万子湖站5、10月份TP将达到III类水标准，东洞庭湖站9月份、小河咀站7~10月份TN将达到III类水标准。

Abstract: In order to study the impact of different water inflow conditions on the hydrodynamic and water quality of Dongting Lake, a two-dimensional hydrodynamic water quality coupling model of Dongting Lake was con-structed in this paper. By changing the hydrodynamic boundary and water quality boundary process of the model, the response process of hydrodynamic and water quality of Dongting Lake under the change of water exchange and pollution load into the lake was simulated and analyzed. The research results show that: 1) After the Three Gorges Project operation, the water inflow into the lake and the hydraulic charac-teristics of the junction between rivers and lakes changed, thus affected the temporal and spatial distribu-tion of hydrodynamic water quality in the lake area. When the Three Gorges Project entered the im-poundment period in October, the water inflow into the lake decreased, and the concentration of TP and TN in the lake area increased as a whole. However, due to the decrease of water inflow from the main stream of the Yangtze River, the hydraulic gradient of the outlet increased, and the concentration of TN and TP in the area from East Tongjongho station to the outlet decreased significantly. 2) When the flow process of the lake inflow in the base year remains unchanged and the overall pollution load in the lake is reduced by 10%, in the West Dongting Lake, The concentration of TP and TN in the north and south of South Dongting Lake decreased significantly. In June and July at East Dongting Lake Station, and in May and October at Wanzi Lake Station, TP will reach Class III water standards. In September, at East Dongting Lake Station and Xiaohezui Station from July to October, TN will reach Class III water standard.