Diagram showing how precipitation water soaks into the ground and, depending of the layers of rock below ground, can take from days to millennia to get back into surface waters.

Groundwater — Right underneath our feet

March 10-16 is National Groundwater Awareness Week, when we give special recognition to one of our nation’s most valuable resources — groundwater.

Groundwater affects everyone.  It supplies the drinking water for nearly half our nation’s population and provides about 40 percent of our irrigation water.  It sustains streamflow between precipitation events and during protracted dry periods. And it helps maintain a variety of aquatic ecosystems that are dependent on groundwater discharge to streams, lakes, and wetlands.

Groundwater is a part of our daily lives.  Rural farmers and urbanites, water-supply managers and regulators, researchers and policy-makers all have a part to play in the current status and future of our groundwater resources.  This valuable resource is right underneath our feet.

Groundwater Challenges

The USGS strives to understand the dynamics of the many demands for groundwater from both human and environmental uses.  Understanding these dynamics helps answer important questions about current groundwater availability and long-term sustainability.

In many states, groundwater is a vital source of irrigation water for farmers.

Groundwater is everywhere, but its availability varies. Groundwater availability can be compared to a bank account.  An underground aquifer, a resource shared by many users, receives deposits from precipitation and surface water. The many users make withdrawals from the aquifer to irrigate farmlands or supply wells.  If there are too many withdrawals, and not enough steady deposits, there isn’t enough groundwater in the aquifer to go around.

Even when water is plentiful, it’s not truly available unless the quality is acceptable for the intended use.  Both water quantity and quality are essential to maintaining water supply for municipal, domestic, agricultural, and recreational use and for aquatic ecosystems.

Quantity Assessments

The USGS has a legacy of groundwater assessment, publishing the first national assessment of groundwater in the early 1900s.  The USGS is working toward determining water availability in 30-40 major aquifers as part of a national water census.  These aquifer assessments provide objective scientific information about the effects of human activities on water levels, groundwater storage, and discharge to surface-water bodies and explore how climate variability could affect groundwater availability.

Various regional USGS groundwater studies either complete, planned or in progress

Many states are experiencing groundwater decline in places where withdrawals have increased largely in response to economic and population growth.  Many regions in states such as Washington, Oregon, Arizona, Louisiana, Texas and Illinois have experienced lowered groundwater levels by as much as several hundred feet.  In other locations, increased withdrawals have caused saline groundwater to encroach inland.  Extensive groundwater pumping has resulted in land-surface subsidence and sinkholes.  The USGS has recently released a scientific study illustrating  how increased groundwater withdrawals can result in streamflow depletion.  The stress of increased demands on groundwater resources – for domestic supply, municipal supply, irrigation and industrial uses – has decreased availability in some areas.

Quality Assessments

In parallel, USGS groundwater quality assessments assist water-quality managers and regulators in making decisions about monitoring needs and drinking water issues.  The USGS collaborates with other federal, state, and local drinking water programs to conduct extensive monitoring for regulatory and compliance purposes.  The whole of the nation’s groundwater can be divided into 62 principal aquifers; these provide one-third of the Nation’s population their drinking water from public supply systems and 15 percent of the Nation’s population with drinking water  from private domestic wells.  Each aquifer can cover multiple states, yet management decisions are made on the local level.  USGS groundwater quality assessments provide that large-scale perspective on each aquifer, providing consistent information needed by decision-makers.

Cascading aerator at aquifer storage and recovery plant (credit: Cassi L. Otero, USGS)

USGS groundwater quality assessments have shown that many aquifers contain low concentrations of at least one contaminant.  Nitrate and man-made contaminants like insecticides and gasoline chemicals were at levels of potential human-health risk

USGS data assists in conservation

USGS groundwater assessments help inform the public so that citizens across the nation can engage in best practices for management, protection, and conservation.  Groundwater conservation is a matter of both conserving the quantity and protecting the quality from contamination.

Everyone can take steps to do their part.  Excessive well water withdrawals lower the water-level to the point of having to drill deeper to reach water, which can become increasingly expensive to maintain.  To conserve groundwater, individuals can identify routines where water use is highest and where it can be limited.  Individuals can also take steps to prevent groundwater contamination:  1) position wellheads a safe distance from potential contamination; 2) update septic system inspection and cleaning; 3) conduct annual well inspections; 4) properly dispose of hazardous materials; 5) decommission any abandoned wells using a professional.

USGS groundwater availability studies make up an integral part of the Department of Interior’s WaterSMART, which is helping water resource planners and managers tackle America’s water challenges by providing funding, leveraging partnerships, and commissioning projects specifically aimed at understanding and conserving water.  DOI recently released a three-year progress report for WaterSMART, showing that the program is saving water, finding better ways to use water resources more efficiently, and helping partners plan to meet future water demands.

The USGS is dedicated to providing the public with unbiased, timely and relevant information about the Nation’s groundwater resources.  More information on USGS groundwater data, products, publications, and news can be found at the USGS Groundwater Resources  information pages.

The graphic shows various blue spheres representing relative amounts of Earth's water in comparison to the size of the Earth. Are you surprised that these water spheres look so small? They are only small in relation to the size of the Earth. These images attempt to show three dimensions, so each sphere represents "volume." Overall, it shows that in comparison to the volume of the globe the amount of water on the planet is very small - and the oceans are only a "thin film" of water on the surface.

If you took all the water on earth – in oceans, ice caps, lakes, rivers, groundwater, the atmosphere, and living things – and wrapped it into a sphere, it would have a diameter of about 860 miles. That 860-mile-high sphere is represented by the largest bubble in the picture, which stretches from Salt Lake City, Utah to Topeka, Kan. It has a volume of over 332 million cubic miles. If you popped this bubble with a giant pin, the resulting flow would cover the lower 48 states to a depth of about 107 miles.

Climate change will also impact water availability. Projections indicate a steady increase in temperature progressing through the 21st century, generally resulting in snowpack reductions, changes to the timing of snowmelt, altered streamflows, and reductions in soil moisture, all of which could affect water management, agriculture, recreation, hazard mitigation, and ecosystems across the nation. Despite some widespread similarities in climate change trends, climate change will affect specific water basins in the U.S. differently, based on the particular hydrologic and geologic conditions in that area. For example, USGS models project that changes to snow pack in the Sprague River Basin in Oregon (pictured above) could cause annual peak streamflows to occur earlier in the spring as overall basin storage decreases, which may force managers to modify storage operation and reprioritize water deliveries for environmental and human needs.

In reality, most of the largest bubble is stretched over about 70 percent of Earth’s surface, a very thin layer over the land. As we stare out into them, we think of oceans as vast expanses. And in many parts of the world we feel water-rich, even as we hear stories of regions where water is far from abundant. This graphic shows that this amount of water is not nearly as abundant as it may feel.

Furthermore, most of this water is unusable to humans, because we need freshwater to survive, and 98 percent of that large bubble is saline. The much smaller blue sphere over Kentucky – by comparison, about 169.5 miles in diameter – represents the world’s liquid freshwater, including groundwater, lakes, swamp water, and rivers. However, 99 percent of that bubble is groundwater, much of which is not accessible to humans.

Now we can start to answer the question, how much water is available to humans? Do you notice that tiny blue speck over Atlanta, Ga.? That’s the bubble representing freshwater in all the lakes and rivers on the planet. Most of the water that people and ecosystems need every day comes from these surface-water sources. The diameter of this sphere is a mere 34.9 miles, with a volume of a little over 22,000 cubic miles. The sphere looks tiny compared to, say, the Great Lakes region, which is the largest freshwater source on Earth. But keep in mind that tiny dot is about 35 miles high.

In 2005 Americans used about 328 billion gallons of surface water and about 82 billion gallons of groundwater per day. Surface water is used as the primary supply of drinking and irrigation water, but groundwater is used for these purposes too. Groundwater is also vital in keeping rivers and lakes full, and it provides water for people in places where visible water is scarce, such as in the desert towns of the western U.S.

Still – look again at the picture. It doesn’t seem like a lot of water! Certainly, it’s not. It’s important to remember that water is a precious resource. It’s never sitting still; it moves between the air, the land, underground, to the ocean and back again via the water cycle. USGS scientists conduct studies to understand how much water is available now and for the future, including how water flows through the water cycle, how surface water and groundwater interact, and how the quality of our water impacts availability. These studies are important for wise water use, especially as the world becomes increasingly water stressed.

Data behind this Graphic

Water Use in the U.S.

USGS Details Effects of Climate Change on Water Availability in 14 Local Basins Nationwide

Yet because groundwater is a hidden resource lying below the land surface, it suffers from “out of sight, out of mind” syndrome. People often overlook it, underappreciate it, take it for granted.

Unseen and easily neglected, it’s no less important. How much groundwater is available in your neighborhood? What quantities of withdrawal by a new industry or a growing number of new neighbors could be sustained? What about the quality of the groundwater?

USGS Science Making Connections

Example of wellhead plumbing typical of public wells sampled in a USGS study of 932 public wells nationwide. About 105 million people—or more than one-third of the Nation's population—receive their drinking water from one of the 140,000 public water systems across the United States that rely on groundwater pumped from public wells. The USGS studies source (untreated) water collected from public wells before treatment or blending, which often are used by public water systems to decrease contaminant concentrations below levels of potential human-health concern. These types of studies assist water utility managers and regulators in making decisions about future monitoring needs and drinking-water issues. Michael Rosen, USGS.

Understanding the connections between ground and surface water as part of the hydrologic cycle is crucial to successfully managing water resources. Surface water ends up below the surface as groundwater when rain and collected water seep into the ground. Then groundwater flows within an underground aquifer. Later, it discharges at the surface again to a spring, stream, lake, or other surface water body. USGS scientists, in collaboration with federal, state, and local partners are working to better understand how groundwater flow is affected by population, changes in land use, and ecological demands.

Many USGS studies about groundwater availability are local in scope, simply because local studies are crucial for managing this resource on a local level. However, because local groundwater is interconnected with other components of the hydrologic system, including other parts of aquifers and surface water, it is also important to consider the entire aquifer when assessing groundwater availability.

The goal of the USGS GroundwaterResourcesProgram is to document groundwater availability in all of the majoraquifers in the United States. These studies will quantify current aquifer resources, provide a means to evaluate how these resources have changed over time, and provide tools to forecast how much water will be available in the future.

The USGS develops models to understand the interactions between groundwater and surface water. Last year, USGS scientists developed a model for theYakimaBasin in Washington State that will help regulators understand how surface water and groundwater are interconnected. Similar studies are being planned or underway throughout the country through the USGS CooperativeWaterprogram.

USGS researchers are also studying the effect that climate change will have on groundwater.  Climatechange, for example, will affect snowpack, precipitation, water vapor, soil temperature, soil moisture and other aspects of the hydrologic cycle, all of which will also affect groundwater availability.

Great Lakes water availability studies conducted by the U.S. Geological Survey aim to help characterize how much water the Basin has now, how water availability is changing, and how much water it can expect to have in the future.

Groundwater use is also affecting  ouroceansandcoasts through sea level rise. Once water is pumped out of the aquifer system, it doesn’t always go back in at the same rate. This means that excess water (runoff) ends up on the surface and ultimately in the ocean. Groundwater development has significantly increased in the past 50 years, and USGS scientists have found that this increase in use has exacerbated the effects of sea level rise.

Because we depend on high-quality, fresh water — not only for health, but for many industrial and energy uses — groundwater availability is also linked to water quality.  The USGS National Water Quality Program is documenting water quality in the principle aquifers throughout the country while continuing studies to determine which groundwater sources are most vulnerable to contaminants like arsenic, radium, and other trace elements.

National Groundwater Awareness Week

March 11-18, 2012 is the National Groundwater Association’s NationalGroundwaterAwarenessWeek. Learn more about what you can do to protect your groundwater from the NationalGroundwaterAssociation or the U.S. EnvironmentalProtectionAgency.

USGS scientists conducting chemical analyses on site and in an on-site mobile laboratory in order to identify important degradation products from the natural attenuation of landfill leachate in the aquifer.

Natural processes play a big role in removing underground contaminants after a landfill has been closed. Closed landfills are typically unlined and may pose a threat to groundwater quality. USGS scientists study how natural processes can remove landfill contaminants. Recent USGS research shows that climate, vegetation, groundwater recharge rate, and proximity of the contaminants to the water table can all affect and control natural removal rates. The chemical properties of groundwater and aquifer sediments can have a major effect on microbial reactions that remove contaminants. Also, rates of contaminant removal at the center of the subsurface contaminant plume can be very different than rates at the plume’s edges, where contaminated groundwater interacts with uncontaminated groundwater or discharges to surface water. Understanding how effectively natural processes remove contaminants is complicated, and requires examining many environmental factors. For more information on landfill contaminants and other topics related to toxic substances visit our website.

Contact: Isabelle Cozzarelli

Young boys working in a newly cropped field in Africa.

In parts of eastern Africa, drought is of increasing concern, as poor families suffer from food shortages and the inability to grow crops and sustain livestock. Stunted growth in children due to malnutrition has also been linked to climate trends in Africa.

Drought conditions are expected to continue as global temperatures continue to rise and rainfall declines across parts of eastern Africa.

This poses increased risk to millions of people in Africa who currently face potential food shortages.

What’s being done to help?

The USGS is involved in a variety of research efforts to help understand current and future conditions in Africa, helping to inform plans to provide aid.

The Famine Early Warning Systems Network, or FEWS NET, is one endeavor that has already made great strides in helping to address this issue. FEWS NET helps target more than $1.5 billion of assistance to more than 40 countries each year.

FEWS NET examines the populations of the developing world with the most food insecurity, identifying critical situations in which food aid will be needed. These are populations whose livelihoods are typically tied to subsistence rain-fed agriculture and pastoralism.

FEWS NET is sponsored by the U.S. Agency for International Development (USAID) Office of Food for Peace and the USGS is actively involved.

FEWS NET at the United Nations Climate Convention

A USGS presentation on FEWS NET will be a featured side event on November 30, 2011, at the United Nations 17^th annual Conference of the Parties (COP-17) in Durban, South Africa. The convention’s purpose is to develop international agreements and a declaration of policies and practices for combating climate change and its impacts around the world.

A herder moves cattle through a barren landscape in eastern Africa.

Climate forecasts and remote sensing help spot future trouble

FEWS NET has developed its own climate services to provide decision makers with early identification of agricultural drought that might trigger food insecurity. Scientists use climate forecasts to develop forward-looking food security assessments that are based on expected agricultural outcomes for the season ahead.

Since networks of ground observation stations are often sparse or reported late in FEWS NET countries, satellite remote sensing of vegetation and rainfall fills in the gaps. Remote sensing from space allows for rapid, accurate assessments of a broad range of environmental and agricultural conditions. USGS scientists provide the technologies and expertise to support remote sensing for FEWS NET activities.

Early warning of famine in Somalia helps pre-position food supplies

On July 20, 2011, the United Nations declared parts of Somalia as a region of famine. The decision was supported by FEWS NET and USGS observational evidence of conditions in the area.

The declaration was the culmination of early warning communications encouraging — months before the crisis — that government and other agencies pre-position food and supplies in the region.

“None of the many uses of Earth-observing satellites is more vital — or has as much potential for prompting timely humanitarian intervention — as famine early warning,” said USGS Director Marcia McNutt. “Remote sensing from space allows USGS scientists to provide rapid, accurate assessments of a broad range of environmental and agricultural conditions.”

The eastern Horn of Africa, the continental region that encompasses Somalia, has experienced two consecutive seasons of very poor rainfall resulting in the worst drought in 60 years. Crops have failed, livestock deaths are widespread, and food prices are very high. While the rains this winter have been good, food prices remain high, and the food security situation remains insecure.

Stunted growth linked to malnutrition and climate change

Other USGS research is helping to identify the impacts of a changing climate on Africa’s people. Scientists recently discovered that malnutrition and dry hot living conditions are linked to stunted growth in Mali, West Africa.

USGS research found that Mali was becoming substantially warmer and a little bit drier. Scientists also knew that farmers and those who make a living raising sheep, cattle, goats, or camels were poor, and that stunted growth was occurring throughout Mali.

Scientists wondered if there could be a link between human health and increasingly warm and dry conditions.

To investigate, the USGS worked with the University of California, Santa Barbara, to study climate observations and demographic and health data. The Demographic and Health Survey program routinely compiles data from surveys in 90 countries to study trends in health and population. Scientists analyzed statistics on specific villages in Mali and found that there was a link between a warmer climate and increased stunting.

Population growth combined with the impacts of warming will further increase these health impacts.

Stunting was also linked to other factors, such as mother’s education and the water supply system. Women’s education, improved water supplies, and agricultural development could help to address malnutrition and stunting in Mali.

An article on this research was published in in the journal, Applied Geography, by San Diego State University, the University of California, Santa Barbara, and the USGS.

A Food Security Assessment in Somalia found severe impacts on livestock due to drought conditions.

Other studies underway

Other new research includes the discovery that the warming of the Indian and western Pacific oceans (which is linked to global warming) affects rainfall over large areas of the Horn of Africa. As the globe has warmed over the last century, the Indian Ocean and western Pacific have warmed especially fast.

The resulting warmer air and increased humidity over the Indian and western Pacific oceans produce more frequent rainfall in that region. The air loses its moisture during rainfall, and then flows westward and descends over Africa, leading to decreased rain in parts of eastern Africa. Trends toward increased frequency of drought that we are seeing now are likely to continue into the future as warming continues.

A few recent articles on this research were published in the journal, Climate Dynamics, by scientists with the USGS, the University of California, Santa Barbara, and Los Alamos National Laboratory. The most recent article concludes that global warming will lead to a decrease in rainfall during the summer monsoon season, from June to September, across southern Sudan, southern Ethiopia, and northern Uganda.  Another article concluded that eastern Africa, particularly Kenya and southern Ethiopia, will also have a significant decrease in rainfall during the long-rains season from March to June.

USGS scientists are working hard to translate these technical studies into reports for decision makers. To date, they have completed summary fact sheets focused on Sudan and Kenya.

Scientists also found that some regions, like northern Ethiopia, are not getting drier due to current warming temperatures. Rainfall varies dramatically across all of eastern Africa, with high mountainous areas typically receiving many times the rainfall received in low-lying areas. Therefore, agricultural growth in these climatically safe regions could help offset rainfall declines in other locations.

Start with science

Scientists are looking at clues and changes in nature to understand the impacts of global warming. In Africa, impacts are seen across the landscape — on farms and even in humans.

By starting with science, well-informed decisions can be made to help Africa as it faces drought, famine, and health concerns.

FEWS NET partners include the USAID, Chemonics International, the USGS, NASA, NOAA, and the USDA. The Geography Department at the University of California, Santa Barbara, is a partner to the USGS in this effort.

Want more information?

Listen to a podcast interview with USGS scientists as they discuss ongoing efforts to understand conditions in Africa.

Marcia McNutt, USGS Director

March 6-12 is National Groundwater Awareness Week. It is important to recognize that groundwater is a vital natural resources; we should NEVER take for granted the water we drink and use on a daily basis, regardless of its source. We depend on an adequate supply of good quality groundwater for about half of our drinking water needs. We also depend on this resource to provide much of the irrigation water that helps put food on our tables. Everyone has a vested interest in groundwater.

The USGS studies the quantity and quality of the nation’s groundwater. Regional groundwater studies for the High Plains aquifer, the Denver Basin, the Lake Michigan Basin, the North Atlantic Coastal Plain aquifer, and others around the country give states and managers a starting point for understanding how much water is available now and in the future for agriculture, drinking and other uses.

USGS research on groundwater quality also protects citizens from groundwater contamination. For example, USGS research and information on arsenic in groundwater recently led New England States and the U.S. Environmental Protection Agency to recommend testing for arsenic in all private wells in the region. In Florida, USGS scientists are studying saltwater intrusion in the Floridan aquifer, which is the primary drinking water source for over 10 million people. This research is key to ensuring that we as a Nation have the information necessary to make decisions about protecting, preserving and understanding this precious resource.

Groundwater discharge from the Snake River Plain aquifer in the Thousand Springs area, Idaho.

As the primary federal science agency for water resource information, the USGS is proud to work closely with the National Ground Water Association. This past year, we have been collaborating with the Association on a pilot program to test the concept of a National Groundwater Monitoring Network. We applaud the Association’s efforts to inform the public about groundwater and to generate appreciation for this precious resource by designating a week to promote groundwater awareness.

I encourage you to take a moment to learn more about America’s groundwater resources by visiting the USGS groundwater information website or the homepage for the National Ground Water Association’s groundwater awareness week.

Additional Information:

• CoreCast: Groundwater Awareness Week (Episode 146)
• News Release: Groundwater Efforts that Serve Oklahoma Well!
• USGS Groundwater Information
• National Groundwater Awareness Week
• Great Lakes Water Availability

Three-Dimensional Model of the Geologic Framework for the Columbia Plateau Regional Aquifer System.

Learn how 3-D modeling is used to examine groundwater and how this cutting edge science is used to solve tomorrow’s problems today.

Learn more

Agricultural and urban areas contribute to elevated nutrient concentrations

Nutrient sources in both agricultural and urban areas contribute to elevated nutrient concentrations in streams and groundwater across the Nation.

More information