What is groundwater?

Groundwater is water that exists underground in saturated zones beneath the land surface. The upper surface of the saturated zone is called the water table.

Contrary to popular belief, groundwater does not form underground rivers. It fills the pores and fractures in underground materials such as sand, gravel, and other rock, much the same way that water fills a sponge. If groundwater flows naturally out of rock materials or if it can be removed by pumping (in useful amounts), the rock materials are called aquifers.

Groundwater moves slowly, typically at rates of 7-60 centimeters (3-25 inches) per day in an aquifer. As a result, water could remain in an aquifer for hundreds or thousands of years. 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. 

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How can an earthquake affect groundwater or changes in wells?

Groundwater levels in wells may oscillate up and down while seismic waves pass, and in some cases, the water level may remain higher or lower for a period of time after the seismic wavetrain has ended.

How much water is used by people in the United States?

Since 1950, the USGS has collected and analyzed water-use data for the United States and its Territories . That data is revised every 5 years. As of 2015, the United States uses 322 billion gallons of water per day (Bgal/day). The three largest water-use categories were irrigation (118 Bgal/day), thermoelectric power (133 Bgal/day), and public...

How much natural water is there?

Earth is estimated to hold about 1,460,000,000 cubic kilometers of water. The breakdown of where all that water resides is estimated as follows: Oceans (saline) 1,419,120,000 cubic kilometers Ice caps and glaciers (fresh) 31,244,000 cubic kilometers Ground water (fresh and saline) 8,906,000 cubic kilometers Streams and lakes (fresh) 132,860 cubic...

Does the use of pesticides affect our Nation's water quality?

Pesticide use in the United States has increased because not only must we supply our exploding population with food, but crops and food are also grown for export to other countries. The United States has become the largest producer of food products in the world, partly owing to our use of modern chemicals (pesticides) to control the insects, weeds...

Where can I get my well water tested?

Contact your county or state health department or check with your State Certification Officer for a list of state certified laboratories in your area that do water testing. The cost will vary, depending on the laboratory and the test(s), but people usually consider the cost to be reasonable.

What determines if a well will go dry?

A well is said to have gone dry when water levels drop below a pump intake. This does not mean that a dry well will never have water in it again, as the water level may come back through time as recharge increases. The water level in a well depends on a number of things, such as the depth of the well, the type (confined or unconfined) of aquifer...

How can I find the depth to the water table in a specific location?

The depth to the water table can change (rise or fall) depending on the time of year. During the late winter and spring when accumulated snow starts to melt and spring rainfall is plentiful, water on the surface infiltrates into the ground and the water table rises. When water-loving plants start to grow again in the spring and precipitation gives...

What is the Ground Water Atlas of the United States?

This Ground Water Atlas of the United States is a series of USGS publications that describe the location, the extent, and the geologic and hydrologic characteristics of the important aquifers of the Nation. The series consists of 13 chapters that describe the regional groundwater resources that collectively cover 50 States, Puerto Rico, and the U...

If the ground filters water, is groundwater always clean?

Water drawn from a well was once precipitation that fell onto Earth's surface. It seeped into the ground and, over time, occupied the porous space in some subsurface material. Big particles that are in surface streams, such as leaf chunks, will not be seen in groundwater. So, yes, big particles are filtered out by the ground, along with some...

How important is groundwater?

Groundwater, which is in aquifers below the surface of the Earth, is one of the Nation's most important natural resources. Groundwater is the source of about 37 percent of the water that county and city water departments supply to households and businesses (public supply). It provides drinking water for more than 90 percent of the rural population...
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Date published: January 24, 2018

Alaska Earthquake Rattles Florida’s Groundwater Plumbing

At 12:32 am Alaska time on January 23, 2018, a magnitude 7.9 earthquake shook Alaska residents out of their beds and set off fears of a tsunami all down the West Coast. Fortunately, the tsunami was only a few inches in height, but within an hour of the earthquake in Alaska, waves of a different sort were hitting far away in Florida. 

Date published: December 7, 2017

The Quality of the Nation’s Groundwater: Progress on a National Survey

The U.S. Geological Survey is near the midpoint of a complex undertaking to survey the quality of the nation’s largest drinking-water resource.

Current website: https://www.usgs.gov/news/quality-nation-s-groundwater-progress-a-nation...

Date published: October 18, 2017

Study Estimates about 2.1 Million People using Wells High in Arsenic

Most Arsenic Presumed to be From Naturally Occurring Sources

Date published: May 11, 2017

High Levels of Radon Found in Some Wells Across Pennsylvania

A new U.S. Geological Survey study has discovered high levels of radon in wells across certain areas of Pennsylvania.

Date published: March 9, 2017

How Well Do You Know Groundwater

Groundwater, which flows out of sight through aquifers beneath our feet, is one of the Nation’s most important natural resources. In recognition of National Groundwater Awareness Week, March 5–11, 2017, here’s an opportunity to put your knowledge of this vital resource to the test!

Attribution: Water Resources
Date published: January 19, 2017

Groundwater Quality in Eastern U.S.

A regional assessment of untreated groundwater in the combined Valley and Ridge and Piedmont and Blue Ridge aquifers in the eastern United States is now available from the U.S. Geological Survey.

Date published: December 14, 2016

How Much Water Do We Use?

The USGS National Water-Use Science project has documented 60 years of water-use from 1950 to 2010 in an interactive map.  Choose a year and pick a category to see how much water your state uses. 

Attribution: Water Resources
Date published: October 11, 2016

Large Precipitation Events are Critical in Replenishing Groundwater Resources

Large precipitation events that occur about every 10 years are a critical source of recharge for replenishing groundwater resources, according to a new study by the U.S. Geological Survey and the Bureau of Reclamation.

Date published: December 16, 2014

High Plains Aquifer Groundwater Levels Continue to Decline

The U.S. Geological Survey has released a new report detailing changes of groundwater levels in the High Plains Aquifer. The report presents water-level change data in the aquifer for two separate periods: from 1950 – the time prior to significant groundwater irrigation development – to 2013, and 2011 to 2013.

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 Groundwater-Level Measurement near Jewel Cave National Monument, SD
March 9, 2018

Groundwater-Level Measurement near Jewel Cave National Monument, SD

USGS groundwater hydrologist, Bill Eldridge, is lowering a transducer into an observation well near Jewel Cave National Monument to monitor water-level changes in the Madison aquifer. The data collected will be used to update previously published groundwater-altitude maps to help better understand groundwater flow. The work is being conducted in cooperation with the

...
With property owner's permission, a USGS hydrologist collects a water sample from a private well in Gem County, Idaho
November 1, 2017

Collecting groundwater quality sample

With property owner's permission, a USGS hydrologist collects a water sample from a private well in Gem County, Idaho

Measuring the groundwater level in a well near Lame Deer, Montana
July 25, 2017

Measuring the groundwater level in a well near Lame Deer, Montana

Measuring the groundwater level in a well near Lame Deer, Montana

April 27, 2017

Potential Corrosivity of Untreated Groundwater in the United States

  • Corrosive groundwater, if untreated, can dissolve lead and other metals from pipes.
  • National maps have been prepared to identify the occurrence of potentially corrosive groundwater in the U.S.
  • These findings have the greatest implication for the 44 million people dependent on domestic wells for drinking water.
Flowing groundwater site in Indiana
March 16, 2017

Flowing groundwater site in Indiana

Flowing groundwater site in Indiana

Photo of USGS scientist testing groundwater samples for water quality. 
September 16, 2015

USGS scientist tests groundwater samples for water quality. 

USGS scientist tests groundwater samples for water quality. 

The USGS is near the midpoint of a complex undertaking to survey the quality of the nation’s largest drinking-water resource. From 2012 – 2023, the USGS is assessing groundwater throughout the country through extensive sampling. The latest results from five regional aquifers are now available. 

Setting up Groundwater Streamgage on Green River nr LaBarge
March 13, 2015

Setting up Groundwater Streamgage on Green River nr LaBarge

Setting up Groundwater Streamgage on Green River nr LaBarge

September 22, 2011

PubTalk 9/2011 — Tracking the Nation's Groundwater Reserves

--issues facing current and future water supplies

by William Alley, USGS Office of Groundwater

 

  • Ground water is among the Nation's most important natural resources, providing half of our drinking water as well as being essential to agriculture and industry, and the health of ecosystems throughout the country
...
Real-time Groundwater Streamgage equipment set up
June 15, 2011

Real-time Groundwater Streamgage equipment set up

Real-time Groundwater Streamgage equipment set up

Groundwater Recorder on a well in New Jersey
August 1, 2002

Groundwater Monitoring

Data recorder in a field well shelter monitoring a well in New Jersey