海岸带城市地下水分布特征

我国城市海岸带地下水类型和分布主要受控于陆地地质作用，尤以大地构造作用和河流地质作用为主导。松散沉积物类海岸带地下水为孔隙水，含水介质单一，空间变化大，地下水的赋存和分布规律亦相应复杂。以距今78万年晚更新世为界线，可将第四纪松散沉积物含水层组划分为上（浅）下（深）两层（部）。下部的全新统（Q4）和上更新统（Q3）含水岩组以微咸水、咸水多见；上部的中更新统（Q2）和下更新统（Q1）分布有淡水，部分地下淡水资源有一定的供水意义。基岩类海岸带地下水主要为裂隙水和岩溶水，多为淡水，其水资源量与当地的降水量和基岩入渗系数的大小有直接关系。除砂砾石台地的基岩类海岸带、少数溺谷型泥质海岸带的河谷内和碳酸盐岩分布区外，一般无集中供水意义。

Distribution of different types of Groundwater in Coastal City

By analysis of Q cluster and characteristic factor matrix, some basic types and distributions ware found by selecting 7 characteristic factors in 26 districts of coastal zone. In the view of environmental hydrology, China Coastal Zone would be divided into 2 basic groups （ sedimentary coast and rocky coast） and 6 subgroups （ sandy coast, muddy coast, strongly hydrodynamic coast, massive bedrock coast, grit bedrock coast, bank slope ＆ platform coast）. Distributions of groundwater are mainly controlled by land geology action, particularly by tectonism and hydraulic conditions, and ocean geology action takes part in only changing factor. In the way of water resources, surface water resources were widely utilized in south coastal cities and groundwater water resources took more main role in north coastal cities. The mediums of sediment coast aquifer are simple, but the structure of aquifer is relatively complexity and the change of phase is quick. There are much salt shallow groundwater and abundant fresh groundwater in deep grit aquifer of Pleistocene Epoch in sedimentary coast. Being heterogeneous medium, it can not be probable that has abundant fresh groundwater in fissure aquifer, although the water quality is good. The types of bedrock coastal aquifer are simple, but hydrologic structure is comparatively simple. Sometimes, there are fresh groundwater resources only in river valley or carbonate rock nearly estuary.