大型浅水湖泊水质模型边界负荷敏感性分析

为探究太湖水质对外源负荷削减的时空响应分异性，阐明不同入湖水量和污染来源条件下对应的外源削减侧重点，基于EFDC模型构建太湖水质模型，将太湖入湖边界划分为7组，以COD和氨氮为输出目标，采用局部敏感性分析方法进行太湖水质边界敏感性分析.结果表明，各湖区的COD和氨氮改善响应特点为自削减边界向外围递减，边界敏感性指数均为西北湖区最高.枯水期削减条件下COD浓度改善率比丰水期低28.40%~34.71%，边界敏感性排序为西北湖区边界 > 竺山湖边界 > 贡湖边界 > 梅梁湾边界 > 西南湖区边界 > 东部湖区边界 > 东太湖边界；枯水期削减条件下氨氮浓度改善率比丰水期高41.59%~42.34%，边界敏感性排序为西北湖区边界 > 梅梁湾边界 > 竺山湖边界 > 贡湖边界 > 西南湖区边界 > 东太湖边界 > 东部湖区边界.因此，在进行大型湖泊外源污染防控决策时，需要根据不同水质考核指标综合考虑削减的时期和入湖河流位置.

Sensitivity Analysis of Boundary Load Reduction in a Large Shallow Lake Water Quality Model

To explore the spatial and temporal response of water quality to external load reduction in Lake Taihu, Jiangsu Province, China, and clarify the exogenous load reduction under different water inflow and pollution conditions, a water quality model was constructed and the inflow boundaries were divided into seven groups based on the EFDC model. Taking COD and ammonia nitrogen as output targets, the sensitivities of Taihu Lake water quality boundaries were analyzed using a local sensitivity analysis. The results showed that COD and ammonia nitrogen concentrations of each lake area were more sensitive to the boundary load of the lake area than the rest of the lake area, and the sensitivity index was the highest in the Northwest Lake area. Furthermore, the improvement rates of mean COD concentrations in the whole lake decreased by 28.40%-34.71% in the dry season relative to the wet season, and the ranked sensitivity order of the boundaries was as follows:Northwest Lake boundary > Zhushan Lake boundary > Gonghu Lake boundary > Meiliang Bay boundary > Southwest Lake area boundary > Eastern Lake area boundary > East Lake Taihu boundary. The average improvement rates of ammonia nitrogen concentrations in the whole lake were 41.59%-42.34% higher in the dry season relative to the wet season, and the ranked boundary sensitivity order was as follows:Northwest Lake boundary > Meiliang Bay boundary > Zhushan Lake boundary > Gonghu Lake boundary > Southwest Lake boundary > East Lake Taihu boundary > Eastern Lake area boundary. This difference was affected by algal growth and metabolism, and artificial water diversion and drainage. Therefore, it is necessary to consider the reduction period and inflow location according to different water-quality indicators when planning external prevention and control measures in large lakes.