USGS - Science for a changing world

Understanding the connections that determine groundwater availability

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Across the country, about half of the American public uses groundwater as a primary drinking source. Groundwater is also a critical resource for agriculture, energy production, and a vast array of industries.

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.