ABSTRACT
An aquifer is a geologic formation that can transmit, store, and yield significant quantities of water. An aquifer can be confined (one bounded above and below by impervious formations), unconfined (one with a water table serving as its upper boundary), or leaky (one that can gain or lose water through adjacent semipervious formations). In addition to the aforementioned porous-media aquifers, there are karst aquifers in which water flow is concentrated along fractures, fissures, conduits, and other interconnected openings. The hydraulic properties of aquifers (e.g., transmissivity and storativity) are best determined by testing the aquifers in place. Water contained in an aquifer is called ground water and is commonly extracted by means of a well. The quality of ground water determines, to a large extent, its suitability for a particular use, such as irrigation, public water supply, etc. Human activity poses a threat to ground-water quality and already has resulted in incidents of ground-water pollution or contamination. Because ground water tends to move slowly, it may take many years after the start of pollution before contaminated water shows up in a well. The best way to protect the quality of ground water is to prevent its contamination.
