Characteristics Of Hydrodynamics And Hydrochemistry In The Coastal Zone Near Beihai

The city of Beihai lies in the northern coast of the Beibuwan Gulf, which is in theSouth China Sea. Fresh-water/Salt-water transition zone distributes very widely in thecoastal aquifer in Beihai. In 1980s, sea water intrusion began to happen in Beihai. Soin this case, the paper illustrates the characteristics of hydrodynamics andhrdrochemistry in the coastal zone in Beihai,which can prevent and avoid the seawater intrusion availably in Beihai, also, can protect the local groundwater resourceeffectively.The paper concludes that the groundwater level is of periodic variation apparently,in the meanwhile, the groundwater level is influenced by the rain, production volumeand the sea water. The groundwater level is approximately linear relationship with thedepth of the well. In the aspecet of groundwater hydrochemistry, the water type ischloride chiefly in the coastal zone. From the south to the north, the groundwatervaries from the soft water to the hard water, and the hardness of the groundwater isprincipally attributed to the permanent hardness. pH is generally less than 6.5. Thewhole groundwater system is in the oxidation environment.The emphases of this paper is on researching the characteristic of the Cl^- in thegroundwater in the researched area. In the normal condition, Cl^- content is generallylow (<50mg/L), in the case of the sea water intrusion, Cl^- content will increase sharplyto thousands of mg/L. Cl^- is more higher in the north than that of in the south. It isalso found that the Cl^- is approximately linear relationship with TDS, Na+(Na⁺+K⁺).By using calculating the grey degree of the association with Cl^- and TDS,Na⁺(Na⁺+K⁺), Ca²⁺, Mg²⁺, pH, precipitation, it is concluded that Cl^- content isinfluenced chiefly by TDS and the sea water, besides, is influenced by the soluble saltin the soil and the rain. In addition to this, it is maybe that the low content of Cl^- in thesoil soluble salt and the rain are the main reasons to the low content of Cl^- in theBeihai coastal zone in the normal condition.