Extended Explanation

My Aquifer > Groundwater Basics > How does an aquifer work?


Figure 6 is a simple cartoon showing three different types of aquifers: Vocabulary Term!confined, Vocabulary Term!unconfined, and Vocabulary Term!perched. Recharge zones are typically at higher altitudes but can occur wherever water enters an aquifer, such as from rain, snowmelt, river and reservoir leakage, or from irrigation. Discharge zones can occur anywhere; in the diagram, discharge occurs not only in springs near the stream and in wetlands at low altitude, and also from wells and high-altitude springs.

The amount of water in storage in an aquifer is reflected in the elevation of its Vocabulary Term!water table. If the rate of recharge is less than the natural discharge rate plus well production, the water table will decline and the aquifer's storage will decrease. A perched aquifer's water table is usually highly sensitive to the amount of seasonal recharge so a perched aquifer typically can go dry in summers or during drought years.