When ships pass through a lock in the canal that connects the rivers and sea, the salt in seawater would invade into the freshwater area by the density current to affect the regional water quality of freshwater area and the living environment of fresh-water aquatics. To analyze the saline exchange and transport characteristic during ship lock operation process, taking the pro-posed ship lock in Nicaragua Canal as the research object, we set up a coupling saline exchange model and three-dimension nu-merical model to simulate the step by step intrusion process of sea water into all step locks chambers and the further transportation into the upstream fresh water area. The simulation results show that salinity changes periodically in all step locks chambers and upstream waterway and reaches to a dynamic balance after a period of ship lock operation. The upstream saline transportation can be divided into density current section, transition section and diffusion section. Saline intrusion quantity in one cycle reduces gradually and trends to be steady with the operation time increasing. Based on the simulation results of coupling mathematical model, a differential equation is set up to predict the average salinity in Nicaragua Lake. The computing results show that the sa-linity of lake water in future is far less than salinity bearing capacity of environment.%江海连通运河中的船舶过闸时,海水中的盐分会在异重流作用下向淡水水域入侵,进而影响淡水水域的水质及淡水生物的生存环境. 为了分析船闸运行过程中盐分沿程交换与输运特征,以尼加拉瓜运河上的拟建船闸为例,通过建立耦合的盐分交换分析模型和三维数值模型,模拟计算了海水逐级入侵各级闸室并向上游淡水水域输运的过程. 模拟结果表明:各闸室与上游航道各断面的盐度呈周期性变化,在船闸运行一段时间后逐步趋于动态平衡;上游航道盐度输运可分为异重流段、过渡段和扩散段;一个循环内入侵上游航道的盐量随着船闸运行时间的增加逐渐减小并趋于恒定值. 基于耦合数学的模拟结果,建立微分方程对尼加拉瓜湖的湖水平均盐度进行了预测,计算结果表明湖水远期盐度远小于环境承受盐度.
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