海水入侵的实验研究

An experimental study of seawater intrusion

在海岸含水层中,含较多盐分的海水向陆地方向入侵形成淡-咸水交界面,通常称为海水入侵界面。该界面的动态变化受气象、水文地质和人类活动等因素的影响,是海水入侵问题的主要研究内容。本文介绍了海水向含水层中入侵的室内实验研究,以着色海水和图像处理方法获得入侵界面的形态及其动态变化。实验方法先进,所得数据整体性强,精度高,而且观测方法对流场没有干扰,比传统的提取水样进行化验的方法更有效。实验中模拟了海洋潮汐条件,揭示了入侵界面在不同实验条件下的动态特征。应用数值模拟方法揭示了流场的特征。计算表明,流场分两个区———淡水区和咸水区,由入侵界面分开。淡水区的水流相对活跃,淡水由入侵界面以上区域渗出边界,在界面以上形成淡水通道。

A freshwater-saltwater interface develops in coastal aquifers with the more saline seawater underlying the less saline groundwater. Intensive research work has been done on the dynamic behavior of the fresh-salt water interface, which is mainly affected by climate, hydrogeology of the aquifers and human activities. This paper presents laboratory experiments on the dynamic characteristics of the fresh-salt water interface. A dye solution is introduced and image-processing technique is implemented in the experiments in order to obtain the spatial distribution of salt concentration within the interface. This technique does not disturb the flow field, and is capable of obtaining accurate and spatially continuous concentration data for the flow field. It is proved to be more efficient than the traditional water-sampling method. Tidal variations are included in the experiments at the seaward end to simulate the periodic change in sea level, and results are presented to demonstrate the response of the interface to the tidal conditions. Numerical modeling is also performed to interpret the flow patterns in the presence of the intruded interface under the experimental conditions. It is found that the flow field consists of two flow regimes, a freshwater zone and a saltwater zone, which are separated by the interface. The flow is more active in the freshwater zone than in the saltwater zone, with freshwater flows over the saltwater forming a water-flow channel over the interface. Experimental techniques and procedures presented in this paper may be of reference value for conducting similar experiments in China. Furthermore, the experimental conditions and data are also believed to be valuable for modeling practice, such as model testing, validation or comparisons.