南四湖水质控制方案实施的水质模拟与效果评估

南四湖是保障南水北调东线工程调水水质安全的重要输水通道,对其水质保障综合控制方案阶段实施的输水干线水质改善进行效果评估具有重要的现实意义。基于SMS软件建立了南四湖二维水流水质数学模型,进行了计算边界简化、网格划分、参数选取与设置、模型调试与检验等研究工作,确定了各计算方案的水力学和水质边界条件,模拟计算了南四湖上、下级湖调水期的二维流场和浓度场。结果表明:南四湖流域全面实施"治、用、保"流域综合治污体系,并发挥综合效益的控制方案4的水质最好,同一控制方案输水主航道的水质最好;上级湖控制方案4的调水出湖口CODCr为19.81mg/L,达到地表水Ⅲ类标准,TP为0.053 4mg/L,达到地表水Ⅲ类(河流)标准,但未达到地表水Ⅲ类(湖泊)标准;下级湖各控制方案的调水出湖口CODCr和TP均达到地表水Ⅲ类(湖泊)标准,且在相同工况下,下级湖水质优于上级湖;南四湖上、下级湖输水水质模拟计算结果与各水质保障综合控制方案的总排放量相一致,即总排放量大的控制方案其调水出湖口的污染物浓度也高。

Simulation and Effect Evaluation of Nansi Lake's Water Quality Control Project

Nansi Lake is an important water delivery passage in protecting the safety of water quality in the East Route of the South-to-North Water Transfer Project,and the effect evaluation of the water quality improvement of the water delivery artery,which is implemented under the comprehensive control scheme of water quality security,has important practical significance.Based on SMS software,this study sets up two-dimensional flow-pollutant mathematical model in Nansi Lake and takes the researches such as computation boundary simplification,meshing,the selection and setting of parameters,model debugging and testing.Then the study confirms the hydraulics and water quality boundary condition of different numerical schemes,and finally it imitates and calculates the two-dimensional flow-pollutant in the upper lake and the lower lake of Nansi Lake using the data of water transfer.Analytical results indicate that under the full implementation of the "governance,use and maintenance" of river-basin contamination system,the water quality of Control Scheme 4 is the best,and the water quality of the main channel of water delivery is also the best for the same control scheme.The drainage lake’s CODCr of the water transfer in Control Scheme 4 in the upper lake is 19.81mg/L,which reaches Type Ⅲ of the surface water standard,and the total phosphorus is 0.0534mg/L,which reaches Type Ⅲ of the surface water for the river standard but dose not reach Type Ⅲ of the surface water for the lake standard.The drainage lake’s CODCr and total phosphorus of the water transfer of all control schemes in the lower lake reach Type Ⅲ of the surface water for the lake standard,and in the same working condition,the water quality in the lower lake is better than that in the upper lake.The delivery water quality simulation result is the same with the total discharge of the comprehensive control scheme of water quality guarantee.