Groundwater is formed when precipitation such as rain or snow infiltrates into the ground and accumulates in water-bearing layers.

Suitable aquifers are often composed of:

* Gravel
* Sand
* Coarse gravel deposits
* Fractured limestone
* Fractured bedrock

Less suitable formations include:

* Clay
* Dense loam layers
* Massive, unfractured rock

In practice, it is not only important to know whether groundwater is present, but also:

* How much water is available
* The quality of the water
* Whether the yield is sufficient in the long term