大陆岛地下水动力学特征——以湛江东海岛为例

The hydrodynamic characteristics of groundwater in continental island—an example from Donghai Island,Zhanjiang

东海岛是一具有独特水文地质条件的大陆岛,浅层含水层与大陆以浅海湾相隔,中深层承压水含水层与大陆地下水系统紧密相连。为了深入地认识大陆岛地下水水动力学特征,以湛江东海岛为例,阐述了其水文地质条件,并分析了东海岛浅、中、深层地下水的流场和动态特征。分析结果表明,东海岛为一个典型且独特的大陆岛,岛内和大陆的部分浅层含水层由湛江湾相隔,岛内中、深层含水层和大陆中、深层含水层通过湛江湾相连,且具有统一的水位分布,并保持着密切的水力联系,岛内中、深层地下水由南向北径流补给湛江市区的降落漏斗中心;滨海及海水区域浅层含水层及其下伏的粘土层构成了防止海水入侵中、深层地下水的保护层;浅层地下水流场基本保持天然状态,水位动态特征主要为入渗径流型,水位变化与降雨量相关;中、深层地下水流场以人工流场为主,地下水由南向北径流,水位动态类型主要为开采动态型,水位变化主要受到开采量变化的影响;在近海岸地区,地下水动态表现为潮汐效应型,在潮汐作用下,地下水位动态具有周期性。

The Donghai Island is a continental island with special hydrogeological conditions, where the shallow aquifer is separated from the mainland aquifer by the gulf, but the middle and deep confined aquifers arc closely linked with the mainland aquifers. For in-depth understanding of the hydrodynamic characteristics of the groundwater in the continental island, the hydrogeological conditions of the Donghai Island is described and the groundwater flow and dynamic characteristics are analyzed. The results show that the Donghai Island is a typical and unique continental island, the shallow aquifer is separated from the mainland aquifer by the Zhanjiang Bay, but the middle and deep confined aquifers are closely linked with the mainland aquifers. There is a uniform distribution of groundwater levels in the middle and deep aquifers in the mainland and the island, and the groundwater in the island flows from south to north and supplies the center of the cone of depression in groundwater levels near the city of Zhanjiang. The shallow aquifer of the coastal and marine areas and the underlying clay layer constitute the protective layers to prevent seawater intrusion into the middle and deep aquifers. The shallow groundwater flow field remained the natural state. The dynamic characteristics of the shallow groundwater in which groundwater level varies with the rainfall are an infiltration/runoff-type. The middle and deep groundwater flow field is controlled by the pumping and groundwater flows from south to north. The groundwater dynamic type of the middle and deep aquifers in which groundwater levels are mainly affected by the impact of the extraction variation is exploitation-dynamic type. Near the coastal area, the groundwater dynamic is the tidal effect-dynamic type. With the tidal effect, the groundwater level fluctuates periodically.