白洋淀水质改善方案优化及实施效果研究

Water Quality Optimization Schemes and Ecological Effect Assessment in Baiyangdian Lake

模拟与分析白洋淀试点区域水质改善工程前后的水质变化情况,探索水质改善效果,为白洋淀水质改善提供思路与经验。基于实测地形、气象数据、水质监测数据、现状污染源、大气沉降、风扰底泥释放等数据资料,运用MIKE软件构建了白洋淀二维水动力和水质数学模型,选取现状水量未清淤(方案一)、增加补水流量1.5倍+未清淤(方案二)、增加补水流量2.0倍+清淤0.1 m(方案三)、增加补水流量2.0倍+清淤0.2 m(方案四)4种优化方案,模拟了典型时刻下白洋淀区域内的流场分布形态和主要污染物迁移扩散规律。结果表明:白洋淀淀区内水体流动速度普遍较小,在增大补水流量和清淤的情况下,流场的改变集中于入淀河流的下游,几乎不改变主淀中的流场分布。随着清淤深度的增大,底泥的污染物释放作用进一步削弱,但削弱的幅度较小。由此确定对白洋淀底泥厚度较大、水质污染较为严重的区域开展清淤工作,建议清淤厚度0.2 m左右。在清淤的基础上,对淀区进行合理补水,入口河流选用常年水质较好的河段,建议补水体积不超过现状补水方案的2倍。

In this study, we simulated the hydrodynamic conditions of Baiyangdian Lake under different water quality optimization schemes and analyzed the water quality changes. The aim of the study was to explore the methods to improve water quality of Baiyangdian Lake. Based on the observed terrain, meteorological data, water quality monitoring data, current pollution sources, atmospheric subsidence and winddisturbed sediment release, a two-dimensional hydrodynamic and water quality mathematical model of Baiyangdian Lake was developed by using MIKE software. Four optimization schemes of increasing water replenishment flow and partial sediment dredging were selected, including current water replenishment with no sediment dredging, 1.5 times of current water replenishment with no sediment dredging, 2.0 times of current water replenishment with 0.1 m thick sediment dredging, 2.0 times of current water replenishment with 0.2 m thick sediment dredging, and the flow field distribution and the rules of the primary pollutant migration and diffusion in Baiyangdian Lake were simulated under the four water quality optimization schemes. Results show that the water flow speed in Baiyangdian district was generally slow. In the case of increasing water replenishment flow and sediment dredging, the change of flow field was concentrated in the lower reaches of the inflow river, and the distribution of flow field in the main river was hardly changed. With the increase of sediment dredging depth, the pollutant release of sediment was further weakened, but the weakening degree was small.Therefore, it is suggested to carry out sediment dredging in the area with thick sediment and serious water pollution in Baiyangdian Lake, and the dredging thickness should be about 0.2 m. On the basis of the dredging work, the water should be replenished reasonably in Baiyangdian Lake basin. The inlet river for water replenishment should be selected with good water quality all the year round in case of the secondary pollution and the volume of water replenishment should not exceed 2 times of the current water replenishment volume. The research results can provide ideas and experience for the improvement of water quality in Baiyangdian Lake and have important scientific and engineering significance for the construction of water ecological civilization in Xiongan New Area.