Operator terms · Water
What is groundwater?
Groundwater is water held underground in the spaces of soil and rock, pumped to the surface through wells. It is usually clearer and more consistent than surface water, but it can carry dissolved minerals and, in some places, natural contaminants that treatment must address.
Last reviewed 2026-08-03
Where it comes from
Rain and surface water soak down and collect in an aquifer, a layer of rock or sand that holds water. A well drilled into the aquifer lets a pump bring that water to the surface for treatment and use.
How it differs from surface water
Groundwater is filtered by the soil, so it is usually low in turbidity and steady in quality. It can, though, pick up hardness, iron, or other dissolved substances that a groundwater system may need to treat.
Common questions
- How is groundwater collected?
- Through wells drilled into a water-bearing layer called an aquifer.
- Is groundwater cleaner than surface water?
- Often clearer and steadier, but it can carry dissolved minerals or natural contaminants.
- What is an aquifer?
- An underground layer of rock or sand that holds and yields groundwater.