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Here's how you know
The depth to the water table can change (rise or fall) depending on the time of year. During the late winter and spring when accumulated snow starts to melt and spring rainfall is plentiful, water on the surfaceinfiltrates into the ground and the water table rises. When water-loving plants start to grow again in the spring and precipitation gives way to hot, dry summers, the water table falls because of evapotranspiration.
The most reliable method of obtaining the depth to the water table at any given time is to measure the water level in a shallow well with a tape.If no wells are available, surface geophysical methods can sometimes be used, depending on surface accessibility for placing electric or acoustic probes.
Databases containing depth-to-water measurementscan also be helpful, though they don't always have current data:
- The USGS National Water Information System (NWIS) hasdepth-to-water measurementsmade in the present and the past. A convenient way to find data for your area is by using the NWIS Mapper and selecting "Groundwater Sites" in the menu on the left. Click on any red groundwater pin to access the data (need to zoom in to change the dots to pins).
- The National Groundwater Monitoring Network is a compilation of groundwater monitoring wells from federal, state, and local groundwater networks across the nation. Use their Data Portal to zoom in to your area of interest and click on any site.
- Your state government probably maintains a database of drillers' logs that have water levels recorded when a well was drilled, and hydrologic consultants often have reports that contain water level data from shallow boreholes.
Consulting any or all of these sources is a good first step in finding out the depth to the water table.
Learn more:
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The National Field Manual for the Collection of Water-Quality Data (National Field Manual) provides guidelines and standard procedures for USGS personnel who collect data used to assess the quality of the Nation’s surface water and groundwater resources. The manual is published as separate chapters. Learn more: Techniques of Water-Resources Investigations Reports
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...
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...
Where can I get my well water tested?
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Some counties offer free well water testing, so check with your county first. If they don't, use this EPA website to find a list of state-certified laboratories in your area that do water testing, or contact your county or state health department or your State Certification Officer for assistance. Prices will vary depending on the laboratory and the test(s), but most people consider the cost to be...
What is the difference between a confined and an unconfined (water table) aquifer?
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A confined aquifer is an aquifer below the land surface that is saturated with water. Layers of impermeable material are both above and below the aquifer, causing it to be under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer. A water table--or unconfined--aquifer is an aquifer whose upper water surface (water table) is at atmospheric...
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...
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...
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...
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...
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Related Content
- FAQ
Where can I find detailed sampling methods for surface water and groundwater?
The National Field Manual for the Collection of Water-Quality Data (National Field Manual) provides guidelines and standard procedures for USGS personnel who collect data used to assess the quality of the Nation’s surface water and groundwater resources. The manual is published as separate chapters. Learn more: Techniques of Water-Resources Investigations Reports
The National Field Manual for the Collection of Water-Quality Data (National Field Manual) provides guidelines and standard procedures for USGS personnel who collect data used to assess the quality of the Nation’s surface water and groundwater resources. The manual is published as separate chapters. Learn more: Techniques of Water-Resources Investigations Reports
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...
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...
Where can I get my well water tested?
Some counties offer free well water testing, so check with your county first. If they don't, use this EPA website to find a list of state-certified laboratories in your area that do water testing, or contact your county or state health department or your State Certification Officer for assistance. Prices will vary depending on the laboratory and the test(s), but most people consider the cost to be...
Some counties offer free well water testing, so check with your county first. If they don't, use this EPA website to find a list of state-certified laboratories in your area that do water testing, or contact your county or state health department or your State Certification Officer for assistance. Prices will vary depending on the laboratory and the test(s), but most people consider the cost to be...
What is the difference between a confined and an unconfined (water table) aquifer?
A confined aquifer is an aquifer below the land surface that is saturated with water. Layers of impermeable material are both above and below the aquifer, causing it to be under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer. A water table--or unconfined--aquifer is an aquifer whose upper water surface (water table) is at atmospheric...
A confined aquifer is an aquifer below the land surface that is saturated with water. Layers of impermeable material are both above and below the aquifer, causing it to be under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer. A water table--or unconfined--aquifer is an aquifer whose upper water surface (water table) is at atmospheric...
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...
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...
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...
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...
- Multimedia
Measuring Total Well Depth Using a Steel Tape - YouTube
Measuring Water Levels in a Flowing Well
Measuring Groundwater with Steel Tape
Measuring Groundwater with Electric Tape
- Publications
Groundwater studies: principal aquifer surveys
In 1991, the U.S. Congress established the National Water-Quality Assessment (NAWQA) program within the U.S. Geological Survey (USGS) to develop nationally consistent long-term datasets and provide information about the quality of the Nation’s streams and groundwater. The USGS uses objective and reliable data, water-quality models, and systematic scientific studies to assess current water-quality
Authors
Karen R. Burow, Kenneth Belitz
Groundwater technical procedures of the U.S. Geological Survey
A series of groundwater technical procedures documents (GWPDs) has been released by the U.S. Geological Survey, Water-Resources Discipline, for general use by the public. These technical procedures were written in response to the need for standardized technical procedures of many aspects of groundwater science, including site and measuring-point establishment, measurement of water levels, and meas
Authors
William L. Cunningham, Charles W. Schalk
Ground-water availability in the United States
Ground water is among the Nation's most important natural resources. It provides half our drinking water and is essential to the vitality of agriculture and industry, as well as to the health of rivers, wetlands, and estuaries throughout the country. Large-scale development of ground-water resources with accompanying declines in ground-water levels and other effects of pumping has led to concerns
Authors
Thomas E. Reilly, Kevin F. Dennehy, William M. Alley, William L. Cunningham
Sustainability of ground-water resources
The pumpage of fresh ground water in the United States in 1995 was estimated to be approximately 77 billion gallons per day (Solley and others, 1998), which is about 8 percent of the estimated 1 trillion gallons per day of natural recharge to the Nation's ground-water systems (Nace, 1960). From an overall national perspective, the ground-water resource appears ample. Locally, however, the availabi
Authors
William M. Alley, Thomas E. Reilly, O. Lehn Franke
Ground water and surface water: A single resource
The importance of considering ground water and surface water as a single resource has become increasingly evident. Issues related to water supply, water quality, and degradation of aquatic environments are reported on frequently. The interaction of ground water and surface water has been shown to be a significant concern in many of these issues. Contaminated aquifers that discharge to streams can
Authors
Thomas C. Winter, Judson W. Harvey, O. Lehn Franke, William M. Alley
Ground water and the rural homeowner
As the salesmen sang in the musical The Music Man, "You gotta know the territory." This saying is also true when planning to buy or build a house. Learn as much as possible about the land, the water supply, and the septic system of the house before buying or building. Do not just look at the construction aspects or the beauty of the home and surroundings. Be sure to consider the environmental cond
Authors
Roger M. Waller
- News
Alaska Earthquake Rattles Florida’s Groundwater Plumbing
At 12:32 am Alaska time on January 23, 2018, a magnitude 7.9 earthquake shook Alaska residents out of their beds and set off fears of a tsunami all...
How Well Do You Know Groundwater
Groundwater, which flows out of sight through aquifers beneath our feet, is one of the Nation’s most important natural resources. In recognition of Na...
How Much Water Do We Use?
The USGS National Water-Use Science project has documented 60 years of water-use from 1950 to 2010 in an interactive map. Choose a year and pick a...
Helping Desert Communities Find Hidden Water
Desert communities throughout the Southwest are putting water availability at the top of their municipal agendas.
Large Precipitation Events are Critical in Replenishing Groundwater Resources
Large precipitation events that occur about every 10 years are a critical source of recharge for replenishing groundwater resources, according to a ne...
As an expert in hydrogeology and groundwater, my extensive knowledge allows me to provide in-depth insights into the concepts discussed in the provided article. Groundwater is a critical natural resource, and understanding the depth to the water table is essential for various applications, from environmental monitoring to water resource management.
The article primarily discusses the factors influencing the depth to the water table, methods for measuring it, and the importance of groundwater. Here's an analysis of the key concepts:
-
Depth to the Water Table:
- The depth to the water table is influenced by seasonal variations. During late winter and spring, melting snow and increased rainfall cause the water table to rise. In contrast, hot, dry summers lead to a fall in the water table due to evapotranspiration.
- The most reliable method for measuring the depth to the water table is using a tape in a shallow well. Surface geophysical methods can be an alternative if wells are unavailable.
-
Data Sources for Depth-to-Water Measurements:
- The article mentions the USGS National Water Information System (NWIS) and the National Groundwater Monitoring Network as valuable resources for depth-to-water measurements. The NWIS Mapper is highlighted as a tool to access groundwater data for specific areas.
-
Confined and Unconfined Aquifers:
- The distinction between confined and unconfined aquifers is explained. Confined aquifers have impermeable layers both above and below, causing water to be under pressure. Unconfined aquifers, or water table aquifers, have an upper water surface at atmospheric pressure.
-
Ground Water Atlas of the United States:
- The Ground Water Atlas of the United States, a series of USGS publications, is introduced. It describes the location, extent, and characteristics of important aquifers across the nation.
-
Groundwater Quality and Filtration:
- The article clarifies that while groundwater is filtered as it moves through the ground, it doesn't guarantee absolute cleanliness. Large particles are filtered out, along with some minerals and chemicals too small to see.
-
Importance of Groundwater:
- Groundwater is highlighted as a crucial natural resource, providing a significant portion of water for public supply (37%) and serving as the primary drinking water source for over 90% of the rural population.
-
Water Testing and Resources:
- Information is provided on testing well water, including the suggestion to check with county resources for free testing and using state-certified laboratories listed on the EPA website.
-
Additional Resources and Publications:
- Various USGS publications and technical procedures related to groundwater are mentioned, including the National Field Manual for the Collection of Water-Quality Data.
In summary, the article covers a broad spectrum of topics related to groundwater, offering practical advice on measuring water table depth, understanding aquifer types, and utilizing valuable databases and resources provided by the USGS. The depth of knowledge demonstrated here underscores the importance of groundwater in sustaining water supplies and the need for reliable measurement and monitoring techniques.
