Aquifers

An aquifer is a body of permeable rock, sediment, or soil that stores and transmits groundwater. It acts as a natural reservoir, supplying wells and springs. Aquifers occur in sedimentary rocks such as sandstone and limestone, in fractured bedrock, and in unconsolidated deposits like sand and gravel. They are typically overlain by an impermeable or less permeable layer called an aquitard, which confines the water in a confined aquifer. An unconfined aquifer is open to the surface and recharged directly by rainfall through its permeable upper boundary, while a confined aquifer is sandwiched between aquitards and receives recharge at some distance away.

Groundwater moves slowly through pore spaces and fractures, guided by gravity and pressure. Recharge occurs when water from precipitation, rivers, or streams infiltrates the ground; discharge occurs at springs, wetlands, rivers, or via wells. Renewable recharge depends on climate and land cover. Human activities such as pumping groundwater for irrigation and urban use alter water levels; excessive pumping can lower the water table, reduce stream baseflow, and cause subsidence or saltwater intrusion in coastal zones.

Aquifers are central to water supply in many regions, often providing drinking water, irrigation, and industrial use. Protection and sustainable management involve monitoring groundwater levels, protecting recharge zones, controlling contamination sources, and employing artificial recharge or managed aquifer recharge where appropriate. Understanding aquifer properties and natural variability supports planning for droughts and long-term water security.