新沟河延伸拓浚工程实施后,入江排污负荷增加,长江水质受到影响。为掌控污染风险,保护水质安全,通过建立二维水动力水质数学模型,研究在不利条件下,排江水流对长江水质的影响。同时,长江水质不同月份的NH₃-N本底浓度差异较大,导致不同月份允许排污负荷也不同,确定不同本底浓度下最大允许排江负荷具有极大的应用价值。研究结果表明:排江水流在不利条件下对长江局部水质存在较大影响,且排江NH₃-N浓度越高对排江口区域长江水质影响越大。为做好水质风险防范,以邻近水源保护区为保护目标,提出对应长江不同本底状况下工程最大允许排江负荷限值。研究成果可为相关部门采取预防措施进行水质影响风险防范提供参考依据。

The construction of Xingou River dredging and expanding project would affect the water quality of the Yangtze River by increasing the load of discharge. To control the risk of pollution and ensure the safety of water quality, a 2-D hydrodynamic pollutant transport model is built to examine the influence of Xingou River discharge on the water quality of Yangtze River under unfavorable conditions. Meanwhile, the background concentration of NH₃-N in Yangtze River varies remarkably in different months, hence the maximum allowable discharge is also different in different months. The results show that Xingou River discharge has apparent influence on the local water quality of Yangtze River under unfavorable conditions, and a higher NH₃-N concentration would exert greater influence. To prevent from the risk of water pollution and protect the nearby water source conservation district, the maximum allowable discharges in the presence of different background concentrations are given.