基于EFDC模型五大连池水质模拟和富营养化评价研究

Study on water quality simulation and eutrophication assessment in Wudalianchi based on EFDC model

为有效管理和监测湖泊水环境,全面了解湖泊水质时空变化特征,以城市景观湖泊——黑龙江省五大连池为研究对象,采用EFDC模型建立五大连池三维水动力和水质模型,根据2015~2016年各月实测水文与水质数据对模型率定和验证,揭示五大连池水质时间和空间变化特征,设置3种不同情景分析该湖泊富营养化主要影响因素。利用层次分析法评估湖泊水华发生风险。结果表明,构建EFDC模型模拟水温、溶解氧、总氮、总磷、叶绿素a、氨氮在时空关系上符合实测数据年变化规律,模拟值与检测值总体误差不超过30%,证明EFDC模型在五大连池水质水动力模拟中具有可行性。五大连池水质变化与其地形结构、水文特征和营养盐输入密切相关。EFDC模型对设定3种不同负荷情况下水质富营养化状况模拟结果表明,控制污染源污染浓度降低20%情况下,藻类爆发抑制效果最显著,叶绿素a峰值降低33%;农耕期突发暴雨增加50%污染物入流情况下,藻类爆发明显,叶绿素a峰值增加94.4%;截留状态下叶绿素a并无明显降低。此外,层次分析结果表明五大连池水质现状呈富营养化状态,水华风险级别为轻度,说明湖泊中氮磷等污染物堆积,易发生水华。控制污染源入流浓度是抑制藻类爆发、降低水体富营养化程度主要措施。研究成果为五大连池污染突发事件和水质评价提供管控依据。

In order to manage and monitor the spatial and temporal relations of lake water quality, the EFDC model was used to establish a three-dimensional hydrodynamics and water quality model of Wudalianchi, which is an urban landscape lake in Heilongjiang Province. According to the hydrology and water quality monthly monitoring data collected from 2015 to 2016, the model was calibrated and verified, revealing the change of water quality in Wudalianchi in time and space. Three different scenarios were set up to analyze the main factors affecting the eutrophication of the lake. At last, the analytic hierarchy process was used to assess the risk of lake blooms. The results showed that the simulated effects of water temperature, dissolved oxygen, total nitrogen, total phosphorus, chlorophyll a and ammonia nitrogen on the spatial and temporal relationship of EFDC model were consistent with their real annual variation. The overall error between the simulated value and the measured value did not exceed 30%. It proved that the EFDC model was feasible and effective simulation of Wudalianchi water quality hydrodynamic. Then the characteristics of Wudalianchi water quality were analyzed, and a high degree of correlation between water quality changes and geological structure were obtained, hydrological characteristics and nutrient input. The EFDC model simulated the eutrophication of the water under the three different load conditions. The results found that compared with the normal situation, in the control of pollution source pollution concentration reduced by 20% of the case, the algae outbreaks inhibit the most significant effect, so that the peak chlorophyll a decreased by 33%; In the case of sudden rainfall increased by 50% during the farming period, the outbreak of algae was obvious and the peak value of chlorophyll a increased by 94.4%; Chlorophyll a did not decrease significantly in the retained state. In addition, the results of AHP indicated that the water quality of Wudalian Lake was in an eutrophic state, and its risk grade of water bloom was mild. This indicated that the pollutants, such as nitrogen, phosphorus, and other pollutants accumulated in lakes and there was a possibility of occurrence of water bloom phenomenon under certain conditions. Controlling the influent concentration of pollution sources was the main measure to suppress algal blooms and reduced the degree of eutrophication of water bodies. The research results provided an effective basis for decision-making for Wudalianchi pollution emergencies and water quality assessment.