Aquifer
An underground zone of rock or soil that will provide enough water from a well for use by one house, a farm, village or city. Water usually moves quickly through aquifers.

Aquitard
A layer of rock, silt or clay that will not allow water to pass through it fast enough to be used as a water supply. Water moves very slowly through aquitards.

Evaporate
The change of water from a liquid to a vapour (a fine mist of water suspended in air). This happens at the ground surface where soil can dry out between rains.

Percolate
The downward movement of water droplets through gravel, sand, silt or rock.

Saturated zone
The area below the water table where the spaces in gravel, sand, silt or rock are filled with water..

Transpiration
Water is used by plants and animals and sent out into the air as tiny droplets of vapour. You can see the water you transpire (breath out) in cold weather, or watch water vapour condense on a glass mirror or window by breathing on it!

Unsaturated zone
The gravel, sand, silt or rock above the water table where the pores and spaces are filled by both air and water. Water travels through the unsaturated zone to the water table. Water moving down through the unsaturated zone can cause the water table to rise closer to the ground surface after rain or when the snow melts. In dry weather, the water table will move down.

Water cycle
Water moves in a never-ending natural cycle. The water in the atmosphere falls to the earth as rain and snow, and it returns to the atmosphere when it evaporates from the ground, streams, lakes, rivers and oceans.

Water table
The place under the ground surface where water will stand when a hole is dug. All pores and open spaces are filled by water below the water table.

Water vapour
Water vapour condenses into droplets high in the atmosphere forming clouds and returns to the earth again from the clouds, continuing the water cycle..

Well
A hole dug or drilled into the ground to pump from an aquifer. Usually a well looks like a pipe at the ground surface.