Confined Aquifer: Definition, Types, and Characteristics

Definition

A confined aquifer is an aquifer located below the land's surface and is saturated with water. It is bounded above and below by layers of impermeable material, such as clay or shale, that prevent water from entering or leaving the aquifer.

Types of Confined Aquifers

Pressure Confined Aquifer

In a pressure confined aquifer, the water is under pressure and rises above the top of the aquifer when a well is drilled. This type of aquifer is often found in deep sedimentary basins.

Leakage Confined Aquifer

In a leakage confined aquifer, the confining layers are not completely impermeable, allowing some water to leak in or out of the aquifer. This type of aquifer is less common than pressure-confined aquifers.

Characteristics of Confined Aquifers

Confined aquifers have several distinct characteristics:

High Pressure: The water in confined aquifers is under pressure due to the overlying impermeable layers.

Slow Recharge: Recharge of confined aquifers occurs slowly due to the low permeability of the confining layers.

Less Contamination: Confined aquifers are less susceptible to contamination because the confining layers protect them from surface sources of pollution.

Reliable Water Supply: Confined aquifers provide a reliable source of water because their water levels are not as responsive to short-term fluctuations in precipitation.