What is an aquifer?

What is an aquifer?

• A. A layer of permeable rock or soil that stores groundwater and allows it to flow.
• B. A shallow lake near the surface.
• C. A rock with low porosity.
• D. A natural barrier that stops groundwater.

Answer: (A)

An aquifer is a layer of permeable rock or soil that stores groundwater and allows it to flow through the pore spaces and fractures. Groundwater sits in the tiny spaces between grains and in cracks, moving slowly due to gravity and pressure. Permeability is the property that lets water pass through, while porosity is how much space is available to hold water. An aquifer can be unconfined, with a water table that rises and falls as rain and recharge occur, or confined, trapped between less permeable layers and often under pressure. People tap aquifers with wells because these porous layers hold usable water beneath the surface. The other descriptions refer to features that aren’t reservoirs of groundwater: a shallow lake is surface water, rock with low porosity doesn’t store much water, and a natural barrier that stops groundwater is an impermeable layer, not an aquifer.

An aquifer is a layer of permeable rock or soil that stores groundwater and allows it to flow through the pore spaces and fractures. Groundwater sits in the tiny spaces between grains and in cracks, moving slowly due to gravity and pressure. Permeability is the property that lets water pass through, while porosity is how much space is available to hold water. An aquifer can be unconfined, with a water table that rises and falls as rain and recharge occur, or confined, trapped between less permeable layers and often under pressure. People tap aquifers with wells because these porous layers hold usable water beneath the surface. The other descriptions refer to features that aren’t reservoirs of groundwater: a shallow lake is surface water, rock with low porosity doesn’t store much water, and a natural barrier that stops groundwater is an impermeable layer, not an aquifer.