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Groundwater is the water found underground in the cracks and spaces in soil, sand, and rock. Groundwater has been used by humans for thousands of years; today it provides 25% of the fresh water used in the United States, mostly for irrigation and public water supplies.


Water well in New York. Image Credit: Wikimedia Commons user Wknight94

Groundwater is an inevitable result of gravity: if surface water can seep into the ground before it evaporates or flows away, it will. Water also flows through rocks underground and may flow out of the ground into streams, rivers, lakes, or the ocean in places where the land surface is lower than the water table (e.g., at the bottom of a valley or the side of a cliff) – these outflows of groundwater are commonly called “springs”. In this way, surface water and groundwater are intimately linked – in some places, changes in groundwater levels can have major effects on the levels of nearby rivers and lakes, and vice versa.   Read more

Frequently Asked Questions

Case Studies & Factsheets


What is a Dry Well? A dry well is a well that is used to transmit surface water underground and is deeper than its width at the surface (see image, below). Most dry wells are 30 to 70 feet deep and 3 feet wide at the surface. They are lined with perforated casings and can be filled with gravel or...

Cover of Water in the Oil and Gas Industry

Introduction The oil and gas industry consumes and produces water. Water is used to drill and hydraulically fracture (“frack”) wells, refine and process oil and gas, and produce electricity in some natural gas power plants. Water is also naturally present in the rocks that contain oil and gas and...


Introduction Dry wells improve stormwater drainage and aquifer recharge by providing a fast, direct route for rainwater to drain deep into underlying sediment and rock. Dry wells are most common in the western U.S. where clay or caliche layers slow down the natural drainage of water into underlying...


Fresh water from underground Groundwater is any water found underground in the cracks and pores in soil, sand, or rock. Groundwater provides 25% of the fresh water used in the United States.1 It is particularly important for irrigation and domestic uses in arid or remote areas, where surface water...


The Need for Groundwater Management: Sustaining water supplies and preventing hazards In California, surface water from rainfall, snowmelt, and distant rivers rarely meets the state’s urban and agricultural water needs. Groundwater is an essential water source, providing 35% of the fresh water used...


Why water storage? A reliable water supply is essential for economic, environmental, and public health, but natural water supplies vary with the seasons and between years. Water storage, whether in reservoir lakes or underground, helps to ensure that water is available even during droughts....

Cover of Spills in Oil and Natural Gas Fields

Introduction Oilfield spills can harm wildlife and pose a risk to human health if they reach fresh water sources or contaminate soil or air. The enormous size of the oil and gas industry and the huge volumes of oil and produced water that are handled, stored, and transported result in thousands of...

Cover of Groundwater Protection in Oil and Gas Production

Introduction The United States relies on groundwater for roughly 25% of its fresh water.1 This groundwater is found in porous, permeable rocks (aquifers) that often lie close to the Earth’s surface – the deepest freshwater aquifers are found more than 6,000 feet underground,2 but most are much...

Cover of Water Sources for Hydraulic Fracturing

Hydraulic Fracturing and Water Demand Hydraulically fracturing a modern well can require millions of gallons of water for the initial fracturing process. This is a potential problem in arid regions with competing demands for fresh water (i.e. high water stress), such as Colorado and West Texas (see...

Cover of Using Produced Water

Opportunities and Concerns in Using Produced Water Produced water is natural groundwater that is extracted along with oil and gas. It is commonly salty and mixed with oil residues,1 so it must be either disposed of or treated and reused. About 2.5 billion gallons of produced water are extracted...

Cover of Geoscientists in Petroleum and the Environment

Introduction Geoscience – the study of the Earth – underpins our understanding of the many intersections between petroleum and the environment, from the search for resources to the study of air pollutants. Without the work of geoscientists, we would have neither the energy system nor the...

Cover of Induced Seismicity from Oil and Gas Operations

Manmade Earthquakes Any activity that significantly changes the pressure on or fluid content of rocks has the potential to trigger earthquakes. This includes geothermal energy production, water storage in large reservoirs, groundwater extraction, underground injection of water for enhanced oil...

Cover of Petroleum and the Environment - an Introduction

Introduction When oil and gas were first extracted and used on an industrial scale in the 19th century, they provided significant advantages over existing fuels: they were cleaner, easier to transport, and more versatile than coal and biomass (wood, waste, and whale oil). Diesel and gasoline...

Cover of Abandoned Wells

Introduction In 2017, there were one million active oil and gas wells in the United States.1 When a well reaches the end of its productive life, or if it fails to find economic quantities of oil or gas, the well operator is required by regulators to remove all equipment and plug the well to prevent...

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GOLI Online Courses

GOLI Course: Water as One Resource; Image Copyright © Marli Miller, University of Oregon.
Course Type: GOLI Online Course

This course provides an overview of how groundwater and surface water interact, what the implications of these interactions on water resources are, and how water can be more effectively managed if an understanding of these interactions is incorporated.

The course presenters are Ken...

GOLI Course: Desalination as a Source of Fresh Water; Image credit: James Grellier, Licensed under Creative Commons, CC-BY-SA-3.0, via Wikimedia Commons.
Course Type: GOLI Online Course

Fresh water is an increasingly scarce resource in an increasingly populous and water-intensive world. Maintaining an adequate supply of fresh water both nationally and globally will be one of the largest challenges of the 21st century. Desalination of salty water, from both the ocean and the...

GOLI Course: Making Produced Water More Productive; Image credit: USGS/ Doug Duncan
Course Type: GOLI Online Course

Geoscience is essential to our understanding and management of produced water, an inevitable byproduct of oil and gas development. This course provides a scientific and regulatory background of produced water, how it is commonly disposed, what opportunities exist for the re-use of produced water...

GOLI Course: Techniques for Developing High Resolution LNAPL Conceptual Site Models; Image courtesy of Roger Lamb
Course Type: GOLI Online Course

This course is intended for geologists involved in Light Non-Aqueous Phase Liquid (LNAPL) assessment and remediation. This course provides information on the development of high resolution conceptual site models that can be used to guarantee the project goals are met. The class will cover...

GOLI Course: Converting Membrane Interface Probe Sensor Results into VOC NAPL Distribution Information. Image courtesy of Roger Lamb
Course Type: GOLI Online Course

This course will focus on how to use Membrane Interface Probe sensor results in combination with soil and groundwater analytical results to map the distribution of volatile organic chemical non aqueous phase liquids. This course covers guidelines for using direct sensing tools such as the MIHPT...

Geological Surveys Database Publications

1965, Pennsylvania Geological Survey
Somerset County is adjacent to Maryland in the eastern part of the Allegheny Plateau. Outcropping strata range in age from Upper Devonian to Pennsylvanian, and are described in detail and shown in sections. Total thickness is about 8,000 feet. A cross-bedding and paleocurrent study of the...
2018, Minnesota Geological Survey

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2012, New Mexico Bureau of Geology & Minerals

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1985, West Virginia Geological & Economic Survey

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1980, Arizona Geological Survey
On May 3, 1887, a major earthquake shook much of the southwest United States and Mexico, an area of nearly two million square kilometers (Figure 1). This seismic event, with an estimated magnitude of 7.2 (DuBois and Sbar, in press), caused 51 deaths in northern Sonora, and major destruction of...
2003, Pennsylvania Geological Survey

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1953, Ohio Geological Survey

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2016, Illinois State Geological Survey

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1986, Washington Geological Survey

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1991, Florida Geological Survey

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