Groundwater is the largest source of fresh water on Earth - it's kind of a big deal. The USGS monitors, tests, and studies groundwater resources to assure one of our Nation's most precious resources remains viable for future generations.
BACKGROUND
In simplest terms groundwater is what its name implies: water in the ground that fully saturates pores or cracks in soils and rocks. Water underlies the Earth's surface almost everywhere – beneath oceans, hills, valleys, mountains, lakes, and deserts. It is not always easy to get to or clean enough for use without treatment, but it exists essentially everywhere if you dig deep enough. Groundwater may occur close to the surface or it may lie many hundreds of feet below. And not all groundwater is the same age... water at very shallow depths could be just a few hours old, whereas water at great depth may have been there for several thousands years.
Most of the groundwater we extract is stored in and moves slowly through permeable rocks called aquifers. An aquifer may be a layer of gravel or sand, a layer of sandstone or limestone, or a buried rubbly old lava flow - as long as material is saturated enough that it can yield significant quantities of water for extraction. Water is a solvent and dissolves minerals from the rocks with which it comes in contact, so groundwater may contain dissolved minerals and gases that give it a tangy taste that is familiar to many people. The most common dissolved minerals found in groundwater are sodium, calcium, magnesium, potassium, chloride, bicarbonate, and sulfate.
INFORMATION ON GROUNDWATER QUALITY AND QUANTITY
Generally, the quality of water found in groundwater aquifers is acceptable for most common uses like drinking or irrigation. Groundwater is less susceptible to pollution than surface water because as water enters the ground, the soil and rocks naturally filter much of the water as it passes through the ground. However, the quality of groundwater continues to change as people modify landscapes and release pollutants into the environment. The growth of industry, technology, population, and water-use demand has increased the stress on both our land and water resources. Municipal and industrial wastes and chemical fertilizers, herbicides, and pesticides have infiltrated into the soil in certain areas, percolated into local and regional aquifers, and degraded groundwater quality in many parts of the US. Other pollution problems include sewer leakage, faulty septic-tank operation, and landfill leachates. In some areas, intensive pumping of groundwater has caused groundwater tables to drop, salt water to intrude into freshwater aquifers, and land to subside (sink).
For data and information on principal aquifers in the United States:
RELATED USGS RESEARCH
- Water Science School - Groundwater
- Groundwater Use in the U.S.
- Groundwater Watch
- Groundwater for the Nation
ADDITIONAL RESOURCES
- Ground Water and Drinking Water (U.S. Environmental Protection Agency)
- Wellowner.org (National Groundwater Association)
Use the links below to access web pages on examples of USGS groundwater research.
305b Groundwater Quality Monitoring in New York
Below are frequently asked questions associated with USGS groundwater research.
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.S. Virgin Islands. Learn more: Principal Aquifers...
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...
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 water fills a sponge. If groundwater flows...
If the ground filters water, is groundwater always clean?
Water 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 minerals and chemicals that are too small to see. But...
- Overview
Groundwater is the largest source of fresh water on Earth - it's kind of a big deal. The USGS monitors, tests, and studies groundwater resources to assure one of our Nation's most precious resources remains viable for future generations.
BACKGROUND
In simplest terms groundwater is what its name implies: water in the ground that fully saturates pores or cracks in soils and rocks. Water underlies the Earth's surface almost everywhere – beneath oceans, hills, valleys, mountains, lakes, and deserts. It is not always easy to get to or clean enough for use without treatment, but it exists essentially everywhere if you dig deep enough. Groundwater may occur close to the surface or it may lie many hundreds of feet below. And not all groundwater is the same age... water at very shallow depths could be just a few hours old, whereas water at great depth may have been there for several thousands years.
Most of the groundwater we extract is stored in and moves slowly through permeable rocks called aquifers. An aquifer may be a layer of gravel or sand, a layer of sandstone or limestone, or a buried rubbly old lava flow - as long as material is saturated enough that it can yield significant quantities of water for extraction. Water is a solvent and dissolves minerals from the rocks with which it comes in contact, so groundwater may contain dissolved minerals and gases that give it a tangy taste that is familiar to many people. The most common dissolved minerals found in groundwater are sodium, calcium, magnesium, potassium, chloride, bicarbonate, and sulfate.
Sources/Usage: Public Domain.It is difficult to visualize water underground. Groundwater is simply the subsurface water that fully saturates pores or cracks in soils and rocks. Groundwater is replenished by precipitation and, depending on the local climate and geology, is unevenly distributed in both quantity and quality to nearby lakes, rivers, and wetlands. INFORMATION ON GROUNDWATER QUALITY AND QUANTITY
Generally, the quality of water found in groundwater aquifers is acceptable for most common uses like drinking or irrigation. Groundwater is less susceptible to pollution than surface water because as water enters the ground, the soil and rocks naturally filter much of the water as it passes through the ground. However, the quality of groundwater continues to change as people modify landscapes and release pollutants into the environment. The growth of industry, technology, population, and water-use demand has increased the stress on both our land and water resources. Municipal and industrial wastes and chemical fertilizers, herbicides, and pesticides have infiltrated into the soil in certain areas, percolated into local and regional aquifers, and degraded groundwater quality in many parts of the US. Other pollution problems include sewer leakage, faulty septic-tank operation, and landfill leachates. In some areas, intensive pumping of groundwater has caused groundwater tables to drop, salt water to intrude into freshwater aquifers, and land to subside (sink).
For data and information on principal aquifers in the United States:
RELATED USGS RESEARCH
- Water Science School - Groundwater
- Groundwater Use in the U.S.
- Groundwater Watch
- Groundwater for the Nation
ADDITIONAL RESOURCES
- Ground Water and Drinking Water (U.S. Environmental Protection Agency)
- Wellowner.org (National Groundwater Association)
- Science
Use the links below to access web pages on examples of USGS groundwater research.
305b Groundwater Quality Monitoring in New York
Relatively little data describing the quality of groundwater in New York State exists, yet groundwater is used as a source of drinking water by approximately one quarter of the population of the state. The objective of the 305(b) Ambient Groundwater Quality Monitoring project is to quantify and report on ambient groundwater quality from bedrock and glacial-drift aquifers in upstate New York. An... - Data
- Multimedia
- Publications
- Software
- FAQ
Below are frequently asked questions associated with USGS groundwater research.
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.S. Virgin Islands. Learn more: Principal Aquifers...
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...
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 water fills a sponge. If groundwater flows...
If the ground filters water, is groundwater always clean?
Water 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 minerals and chemicals that are too small to see. But...