Groundwater and Aquifers

Section 1What groundwater is

Groundwater is water found below the ground in spaces between soil particles and rock. It comes mainly from rainfall that soaks into the ground. In Jamaica, groundwater is important in some limestone areas because water can move through cracks and underground spaces.

Section 2Aquifers

An aquifer is a layer of rock or sediment that stores water and allows it to flow. Sandstone, gravel, and cracked limestone can make good aquifers. Here's the trick: an aquifer is not an underground river; it is usually water held and moving through spaces in rock.

Section 3Water table

The water table is the upper surface of the saturated zone underground. Below the water table, spaces in the soil and rock are filled with water. Above it, spaces may contain both air and water.

Section 4Porosity and permeability

Porosity means how much open space a rock has to store water. Permeability means how easily water can pass through connected spaces. Watch out: a rock can be porous but not very permeable if the spaces are not connected.

Section 5Artesian basins

An artesian basin forms when groundwater is trapped under pressure between impermeable rock layers. If a well is drilled into the pressured aquifer, water may rise up the well. In plain words, pressure can push groundwater upward without needing a pump at first.