indicators of seawater intrusion - Seasidebasinwatermaster.org

FINAL DRAFTCross-hatchingshows seawatermovement inresponse topumpingFigure 3: Interface Migration in Response to Groundwater Pumping(from Barlow, 2003)As can be inferred from Figure 3, the degree of interface migration depends onthe amount of water pumped from a particular aquifer, as well as the amount ofleakage from overlying or underlying aquifers. Groundwater extracted from thelowest aquifer might be replaced by rainfall recharge, by seawater migratingshoreward, or by groundwater leaking from the overlying aquifer.An additional issue that must be considered with seawater interface migration isthe initial location of the seawater interface. An interface that starts far from theshore may take a considerable amount of time, often on the order of decades, toreach any production or monitoring well. Furthermore, the farther the interfaceis from the pumping well, the more area is available for fresh water to leak fromoverlying aquifers into the producing aquifer. This slows, or may completelystop, seawater intrusion in the pumped aquifer. Downward leakage, however,removes fresh water from overlying aquifers. This leakage may thereforeexacerbate seawater intrusion in the overlying aquifer.Seawater Intrusion Response PlanNovember 19, 2008 A-5