Why should we protect groundwater?

What is it?

Groundwater is any water found under the surface of the ground. It moves through the spaces between the soil particles, or through cracks and channels in bedrock.

How does it get there?

Groundwater is recharged when rain falls or snow melts. Water that doesn't run off to rivers and ponds, or evaporate back into the air, seeps into the ground. It moves down through the spaces between the soil particles (pore spaces) until it reaches the water table. Above the water table, the pore spaces are filled with air, or air and water. Below the water table all the pore spaces are filled with water and the soil is saturated.

The amount of groundwater recharge depends on the ground cover (pavement, lawn or forest), the ground slope, and the soil type. The quality of the recharge water depends on human activities and the presence of contaminants on the ground surface.

Where does it go?

Water is always moving. Below the water table, the groundwater continues to travel through the soil or rock. It may only be underground for a few weeks, remaining close to the surface and discharging into a nearby creek, or it can move deeper, travelling many kilometers over hundreds of years, possibly discharging into a major river or lake.

If the water is travelling through an aquifer it may be pulled into a well. It's then pumped out of the ground for our use and discharged onto the surface as waste water.

What is an aquifer?

The soil below the ground is often layered. These layers can be sand, silt or clay, or a different mixture. In the same way, the solid bedrock below the soil may be layers of different rock types. Some layers are permeable, meaning water can move through them easily. If a permeable layer is saturated and can supply enough water to a well it's called an aquifer. Typical aquifers consist of sand and gravel, or limestone rock that has many interconnecting channels.

Less permeable soils, such as silt and clay, restrict water movement. The presence of a layer of silt and clay (called an aquitard) above an aquifer helps protect the aquifer from being contaminated.