Overpumping Policy The Through-Flow Systems

Marcel Dekker, Inc. 270 Madison Avenue, New York, New York 10016 

Salinization is often observed in heavily pumped coastal wells. This observation is commonly based solely on chlorine concentration data, and is almost always attributed to seawater encroachment, which is made possible because of overpumping. The real cause of salinization has to be investigated in each case with the aid of complete chemical and isotopic analyses. 

Seawater intrusion is usually limited to a distance of 1-2 km from the sea, but it varies. The depth at which seawater-induced salinization occurs increases with the distance of the well from the sea. The invading seawater may have direct hydraulic interconnection with the open sea, or it may originate from a stagnant compartment of seawater that was trapped during past hydrological conditions. The latter case will be recognizable because of the old age of the saline water and by deviations from the present seawater composition, reflecting seawater-rock interactions. 

The need to preserve some degree of seaward drainage has to be taken into account in groundwater management considerations. At the least, periodic drainage to the sea has to be maintained. 

---