长江口北支倒灌盐水团对取水口的影响及流量响应规律

为了研究北支倒灌盐水团对南支取水口水质的影响,构建了A、B1模型模拟盐水团对潮位、水质、盐度的影响。经过验证,发现模型水动力模拟结果及盐度模拟结果与实测数据较为吻合,再利用此模型模拟了大江口北支倒灌盐水团对取水口的影响及流量响应规律。模拟结果表明,北支倒灌盐水团在南支活动呈现以半月为周期下移,倒灌盐水团形成于大潮期间,随着潮差的减小,倒灌逐渐减弱,盐水团逐渐下移;由于盐水团下移的影响,在取水口处的潮平均盐度过程线随着时间呈现较为对称的驼峰形状;在同一取水口盐度,不同流量下潮平均盐度过程线的驼峰最高值随着流量增加逐渐变小,与流量呈指数关系,而最高值出现的时间随着流量增大而逐渐提前。可见流量是控制北支倒灌盐水团对取水口影响的关键因素。

Impact of Brine Group Intruding from North Branch on Intake in Changjiang Estuary and Response Law of Flow

In order to study the impact of saltwater intrusion from the North Branch on the water quality of the intakes in the South Branch, two mathematical models were established to simulate the impact of brine group on tidal level, water quality and salinity. The hydrodynamic simulated results and the salinity simulated results were basicaly consistent with the measured data. The model was used to simulate the impact of brine group intruding from North Branch on intake in Changjiang Estuary and response law of flow. The results show that the saltwater mass in the North Branch moved seaward fortnightly in the South Branch. The mass of saltwater was formed during the spring tide. With the decrease of the tidal range, the intrusion length gradually decreased and the salt mass was moved seaward. Furthermore, the average salinity process line at the water intake presents a symmetrical hump shape. At the same intake, the peak value of the tidal average salinity process line decreased exponentially with the increase of the river discharge. Moreover, the peak value occurs earlier with the increase of the river discharge. Therefore, the river discharge is the key factor that controls the impact of the saltwater mass on the water intake.