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 who do not get their water delivered to them from a county/city water department or private water company.

Even some major cities, such as San Antonio, Texas, rely solely on groundwater for all their needs. About 42 percent of the water used for irrigation comes from groundwater.

Withdrawals of groundwater are expected to rise as the population increases and available sites for surface reservoirs become more limited.

Learn more: Groundwater Use

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Can hydraulic fracturing impact the quality of groundwater or surface water?

Conducted properly, hydraulic fracturing (or “fracking”) has little possibility of contaminating water supplies. Properly constructed wells prevent drilling fluids, hydraulic fracturing fluids, deep saline formation waters, or oil and gas from entering aquifers. Carefully constructed and operated well sites have the ability to contain potential...

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...

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.

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 of the earth infiltrates into the ground and the water table rises. When water-loving plants start to grow again in the spring and...

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 being 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...

Where can I find detailed sampling methods for surface water and groundwater?

USGS protocols for the collection of groundwater and surface-water samples have been published in the report National Field Manual for the Collection of Water-Quality Data. The National Field Manual was published in chapters; copies of each chapter are available online.

How frequently are volatile organic compounds (VOCs) detected in groundwater?

Volatile organic compounds (VOCs), which are widely used in the manufacture of many products including refrigerants, plastics, adhesives, paints, and petroleum products, have been detected in about one-third of the wells sampled by the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey (USGS). Chloroform and other...

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...
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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: 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: 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: November 1, 2016

Helping Desert Communities Find Hidden Water

Desert communities throughout the Southwest are putting water availability at the top of their municipal agendas.

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.

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USGS scientist standing with a pole annotated with land-surface elevation marks at given years at bench mark H 1235 RESET.
January 31, 2017

Land Subsidence near El Nido, CA

National Geodetic Survey vertical control bench mark H1235 RESET in Merced County, California. H 1235 RESET is in the median of State Highway 15. This is one of several bench mark locations used to help measure the largest recent subsidence in the area using repeat surveys. The exact maximum subsidence location is unknown; however, this bench mark has some of the larger

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USGS scientist standing with a pole annotated with land-surface elevation marks at given years at bench mark W 990.
January 31, 2017

Land Subsidence near El Nido, CA

National Geodetic Survey vertical control bench mark W990 CADWR in Merced County, California. W 990 CADWR is on the Mariposa Bypass Bridge on Washington Rd. This is one of several bench mark locations used to help measure the largest recent subsidence in the area using repeat surveys. The exact maximum subsidence location is unknown; however, this bench mark has some of

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Plants in a field
April 2, 2016

Groundwater decline: Irrigation of plants often uses groundwater

Groundwater, which is found in aquifers below the surface of the earth, is one of the nation's most important natural resources. Groundwater provides drinking water for a large portion of the nation's population, supplies business and industries, and is used extensively for irrigation.

Droughts, seasonal variations in precipitation, and pumping affect the height of

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November 20, 2014

PubTalk 11/2014 — Water, Nuts, and the Nation's Fruit Bowl

California's Central Valley Hydrologic Science

by Claudia Faunt, USGS Hydrologist

 

  • Using about 1% of U.S. farmland, California's Central Valley supplies 7% of the U.S. agricultural output (by value) -- 1/4 of the Nation's food, including about half of the Nation's fruits, nuts, and vegetables.
  • Approximately 20
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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
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USGS employee sampling an urban  groundwater well
December 31, 2009

USGS employee sampling an urban groundwater well

USGS employee sampling an urban  groundwater well. Photo from USGS circular 1352 "Water quality in the Glacial Aquifer System, Northern United States, 1993 - 2009.

Attribution: Water Resources
Irrigation groundwater well
December 31, 2008

Irrigation groundwater well

Irrigation groundwater well. Photo from USGS circular 1356 "Water Quality in the Mississippi Embayment-Texas Coastal Uplands Aquifer System and Mississippi River Valley Alluvial Aquifer, South-Central United States, 1994-2008."

Attribution: Water Resources
Irrigation water from a groundwater well on a rice crop field
December 31, 2008

Irrigation water from a groundwater well on a rice crop field

Irrigation water from a groundwater well on a rice crop field. Photo from USGS circular 1356 "Water Quality in the Mississippi Embayment-Texas Coastal Uplands Aquifer System and Mississippi River Valley Alluvial Aquifer, South-Central United States, 1994-2008."

Attribution: Water Resources
Groundwater emerging from a cliff

Groundwater can flow to the land surface as springs

Groundwater flowing out of Minnie Miller Springs, Idaho, USA.

Water Education Poster on Groundwater
October 31, 2018

Groundwater Water Education Poster, Middle School

Water Education Poster of Groundwater, Middle School

Attribution: Water Resources