Groundwater Awareness


Groundwater AwarenessWhat is Groundwater?

Groundwater is the water that soaks into the soil from rain or other precipitation and moves downward to fill cracks and other openings in beds of rocks and sand. It is, therefore, a renewable resource, although renewal rates vary greatly according to environmental conditions.

It also is an abundant natural resource. Of all the freshwater in the world (excluding polar ice caps), 95 percent is groundwater. Surface water (lakes and rivers) only make up three percent of our freshwater.

Groundwater’s Importance to the Environment

Hydrologists estimate, according to the National Geographic Society, U.S. groundwater reserves to be at least 33,000 trillion gallons — equal to the amount discharged into the Gulf of Mexico by the Mississippi River in the past 200 years.

At any given moment, groundwater is 20 to 30 times greater than the amount in all the lakes, streams, and rivers of the United States.

About a quarter of all U.S. rainfall becomes groundwater. Groundwater provides much of the flow of many streams; many lakes and streams are “windows” to the water table. In large part, the flow in a stream represents water that has flowed from the ground into the stream channel. It’s estimated by the U.S. Geological Survey that about 30 percent of U.S. streamflow is from groundwater, although it is higher in some locations and less in others.

All the water of the Earth including the atmosphere, oceans, surface water, and groundwater participates in the natural system we call the hydrologic cycle. As water moves through all these elements repeatedly, the system is truly cyclical.

Groundwater's Importance to People

  • While about 90 percent of our freshwater supplies lie underground, less than 27 percent of the water Americans use comes from underground sources, which illustrates the underutilization of groundwater. [1]
  • The United States uses 79.6 billion gallons per day of fresh groundwater for public supply, private supply, irrigation, livestock, manufacturing, mining, thermoelectric power, and other purposes. [2]
  • California pumps 10.7 billion gallons per day of groundwater for all purposes, a third more as much than the second-ranked state — Texas (8.02 bgd). [3]
  • More than 15.9 million water wells for all purposes serve the United States. [4]
  • Approximately 500,000 new residential wells are constructed annually, according to NGWA estimates. The construction of these vitally needed water supply systems involves the use of more than 18,460 drilling machines by an estimated 8,085 groundwater contracting firms. [5]
  • NGWA has determined that 44 percent of the U.S. population depends on groundwater for its drinking water supply — be it from either a public source or private well. [6]
  • Private household wells constitute the largest share of all water wells in the United States — more than 13.249 million year-round occupied households have their own well. [7]
  • Other kinds of wells are used for municipal systems, industry, agriculture, and quality monitoring. Groundwater accounts for 33 percent of all the water used by U.S. municipalities. [8]
  • Michigan, with an estimated 1,121,075 households served by private water wells, is the largest state market, followed by Pennsylvania, North Carolina, New York, and Florida. [9]
  • Irrigation accounts for the largest use of groundwater in the United States. Some 57.2 billion gallons of groundwater are used daily for agricultural irrigation from 475,796 wells. [10] In 1900, the United States used only 2.2 billion gallons of groundwater daily for irrigation from 17,000 wells.
  • More than 90 percent of the groundwater pumped from the Ogallala, the nation’s largest aquifer underlying some 250,000 square miles stretching from Texas to South Dakota, is used for agricultural irrigation. Representing about one-third of all U.S. irrigated agriculture, it creates about $20 billion annually in food and fiber.
  • If spread across the surface of the entire United States, the Ogallala’s groundwater would cover all 50 states with 1.5 feet of water. Scientists estimate it could take 6,000 years to refill naturally if it were ever to be fully withdrawn. [11]
  • Texas leads the nation in the number of irrigation wells with 81,511. [12]
  • The number of U.S. farms irrigated in 2018 was 231,474. [13]
  • The U.S. energy cost of pumping water for irrigation in 2018 was $2.4 billion, an average of $15,289 per farm. [13]
  • The top five states in irrigated acres in 2018 were California, Nebraska, Arkansas, Texas, and Idaho. These states accounted for 50 percent of U.S.-irrigated acres and 56 percent of water applied. [13]
  • The amount of water used for irrigation in 2018 was 83.4 million acre-feet, down 5.8 percent from 2013 (1 acre-foot = 325,851 gallons). [13]

[1] Estimated Use of Water in the United States in 2005, U.S. Geological Survey Circular 1344, October 2009
[2] Estimated Use of Water in the United States in 2005, U.S. Geological Survey Circular 1344, October 2009
[3] Ibid.
[4] Estimate prepared by the National Ground Water Association from various federal data sources at U.S. Environmental Protection Agency, U.S. Department of Agriculture, and the U.S. Census
[5] Estimate prepared by the National Ground Water Association from various Association-sponsored industry surveys
[6] Resident population of the United States in 2005 was 296,410,404, U.S. Census
[7] American Housing Survey, U.S. Bureau of the Census, 2008
[8] Estimated Use of Water in the United States in 2005, U.S. Geological Survey Circular 1344, October 2009; U.S. Environmental Protection Agency, Drinking Water and Ground Water Statistics 2007, March 2008
[9] U.S. Census, 1990 (best available data by state)
[10] U.S. Department of Agriculture, Farm and Ranch Irrigation Survey 2013, November 2014, and U.S. Geological Survey, June 2018 report on 2015 water use
[11] Scientific American Water 3.0, March 2008; Understanding Water Risks, World Wildlife Fund, March 2009; State of the Water Industry, TechKnowledgey Strategic Group, March 2009
[12] U.S. Department of Agriculture, Farm and Ranch Irrigation Survey 2013, November 2014
[13] Irrigation and Water Management Survey 2018, formerly the Farm and Ranch Irrigation Survey, December 2019


IN OUR OPINION Stormwater - A Beneficial Resource or a Contaminant: Infiltrate With Caution

Stormwater is a valuable resource that, with proper infiltration, can provide new groundwater resour...

Online Program: Empowering Youth for Water Security

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Ground Water Report to the Nation

Our groundwater resources are in serious need of attention. Abundant, high quality, low-cost groundwater resources are fundamental to the long-term growth and vitality of our nation, yet this most important resource is often overlooked, if not neglected. Attention to the protection and management of groundwater has consistently lagged behind that given to surface waters, meaning that historic and current water resource laws and policies deal primarily with the protection and management of our more visible lakes, rivers, and wetlands.The purpose of the Ground Water Report to the Nation is to highlight some of the more prevalent threats to groundwater, share sucess stories, and make recommendations for improved groundwater protection and awareness.  Note: Please visit the Ground Water Report to the Nation topics page for individual chapters of the report.


Overview Of Groundwater Protection Regulations In Oil And Gas States

This report is part of an update to the Ground Water Protection Council’s 2009 Report, State Oil and Gas Regulations Designed to Protect Water Resources.1 The purpose is to document and outline the range of definitions and requirements for protecting groundwater, based on the regulations of oil and gas agencies and water quality protection agencies in 27 oil and gas producing states. The report is divided into two parts, the first documents the groundwater protection standards for oil and gas agencies and the second part addresses the standards for the water quality protection agencies within the same states. The scope is limited to an overview of regulations that address groundwater quality protection standards through policy statements, definitions, technical requirements such as well casing and cementing depths, groundwater classification and groundwater protection standards. 


State Oil & Gas Regulations Designed To Protect Water Resources

The role of state oil and gas agencies in protecting groundwater through investigation and regulatory reform.

Work Groups

No workgroups were found.


No resolutions were found.



Comments on Proposed Clean Water Act Hazardous Substance Worst Case Discharge Planning Regulations

The Ground Water Protection Council ( appreciates the opportunity to providecomments and feedback to the Environmental Protection Agency (EPA) on the proposed changes to 40 CFR Parts 118 and 300. The following comments are intended to broadly address this proposed rule interpretation, but do not necessarily reflect the individual GWPC member state positions or all of their concerns.