Groundwater is the main water resource in the Gaza Strip. The aquifer is intensively exploited through more than four thousands of pumping wells. As a result of its intensive exploitation, the aquifer has been experiencing seawater intrusion in many locations in the Gaza Strip. The groundwater quality changes in both horizontal and vertical directions. Fresh groundwater is not distributed evenly throughout the whole of the Strip. Salinity of the groundwater increases over time due to seawater intrusion and mobilization of incident deep brackish water caused by over-abstraction of the groundwater. In most parts of the Gaza Strip, the chloride and nitrate content of domestic water exceeds the WHO guidelines [9].