Hydrogeology 101

Useful Facts

In Minnesota, groundwater is the source of drinking water for about 75% of all Minnesotans and provides almost all of the water that is used to irrigate agricultural crops. Source: https://www.pca.state.mn.us/water/state-groundwater

Groundwater occurs within the pores and fractures of geologic materials such as sand, gravel, and other rock, much the same way that water occurs in a saturated sponge.

Groundwater can occur in limestone caverns such as those that occur in southeastern Minnesota and flow similar to a slow moving stream; however, the majority of groundwater occurs in saturated pores and fractures of geologic material.

Groundwater moves slowly in an aquifer, typically at a rate of 0.25 feet to 2 feet (horizontally) per day. As a result, groundwater can remain in the aquifer for hundreds to thousands of years until it eventually discharges to a well, spring or other surface water bodies.

Groundwater is the source of about 40 percent of water used for public supplies and about 39 percent of water used for agriculture in the United States.

Definitions

Water Table:

The upper surface or boundary of a saturated zone that is not confined (i.e., unconfined) by an overlying impermeable geologic layer (i.e., clay).

Aquifer:

Water Table:

Saturated geologic material with connected openings that can readily convey adequate quantities of water for useful purposes.

Well:

Water Table:

Artesian Well:

An opening constructed in saturated geologic materials (i.e., aquifer) that is used to remove groundwater in useful quantities.

Artesian Well:

Flowing Artesian Well:

Artesian Well:

A well in which the static water level rises above a confined aquifer.

Flowing Artesian Well:

A well in which the static water level rises above the ground surface and naturally flows out of the well.

Confined Aquifer:

Flowing Artesian Well:

An aquifer that is confined by an overlying and underlying impermeable geologic layer.

Groundwater:

Unconfined Aquifer:

Groundwater:

Water that exists in the openings of completely saturated geologic sediments and rocks beneath the land surface.

Source: https://www.usgs.gov/faqs/what-groundwater

Porosity:

Unconfined Aquifer:

Groundwater:

The openings or voids in geologic materials such as sediments and rocks that is expressed as a percentage respective of the ratio of the volume of the openings to the total volume of the

materials.

Unconfined Aquifer:

An aquifer where there is no impermeable layer between the water table and the ground surface.

Spring:

Hydrogeologist:

Unconfined Aquifer:

Groundwater that naturally flows out of saturated geologic materials.

Hydrogeology:

Hydrogeologist:

The study of the geologic environments that control the occurrence of groundwater and the physical laws that describe the natural and human-induced flow of groundwater Source: Freeze and Cherry, 1979. Prentice-Hall, Inc., Englewood Cliffs, N.J. pp. 604.

Hydrogeologist:

A person who studies the science of hydrogeology with a groundwater flow dynamics and/or water quality emphasis.

HYDROGEOLOGY 101

Useful Facts

Definitions

Water Table:

Water Table:

Water Table:

Aquifer:

Water Table:

Water Table:

Well:

Water Table:

Artesian Well:

Artesian Well:

Flowing Artesian Well:

Artesian Well:

Flowing Artesian Well:

Flowing Artesian Well:

Flowing Artesian Well:

Confined Aquifer:

Flowing Artesian Well:

Flowing Artesian Well:

Groundwater:

Unconfined Aquifer:

Groundwater:

Porosity:

Unconfined Aquifer:

Groundwater:

Unconfined Aquifer:

Unconfined Aquifer:

Unconfined Aquifer:

Spring:

Hydrogeologist:

Unconfined Aquifer:

Hydrogeology:

Hydrogeologist:

Hydrogeologist:

Hydrogeologist:

Hydrogeologist:

Hydrogeologist:

Soil-Pore Water: