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# Water

## Where can I find flood maps?

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## What is the difference between a confined and unconfined aquifer?

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## Does the use of pesticides affect our Nation's water quality? 

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## How much natural water is there?

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The USGS monitors and studies a wide range of water resources and water conditions, including streamflow, groundwater, water quality, and water use and availability.

## Browse Topics

Floods and Droughts

Groundwater and Aquifers

Hydrography

Rivers and Streams

Water Quality

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####                 What are PFAS?              

Perfluoroalkyl and Polyfluoroalkyl Substances, or PFAS, are a group of synthetic chemicals used in a wide variety of common applications, from the linings of fast-food boxes and non-stick cookware to fire-fighting foams and other purposes. Their persistence in the environment and occurrence across the country make them a unique water quality concern. Drinking water quality and potential exposures...

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####   What are PFAS?

Perfluoroalkyl and Polyfluoroalkyl Substances, or PFAS, are a group of synthetic chemicals used in a wide variety of common applications, from the linings of fast-food boxes and non-stick cookware to fire-fighting foams and other purposes. Their persistence in the environment and occurrence across the country make them a unique water quality concern. Drinking water quality and potential exposures...

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####                 How do I find the best place to drill for water on my property?              

Many factors must be considered before deciding where to drill a water well. The most important is to decide how the well will be used. If the well is for drinking water, then local geology, hydrology, and state regulations are important to know. Contact the department in your state government that regulates and tracks water and natural resources. They should have information on licensed drillers...

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####   How do I find the best place to drill for water on my property?

Many factors must be considered before deciding where to drill a water well. The most important is to decide how the well will be used. If the well is for drinking water, then local geology, hydrology, and state regulations are important to know. Contact the department in your state government that regulates and tracks water and natural resources. They should have information on licensed drillers...

Learn More

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####                 Can a drought be relieved by bringing in water from other regions of the country that have excess water?              

Any large-scale projects for mitigating drought in the U.S. would fall under the direction of the Bureau of Reclamation , which is the federal agency tasked with water management. While technically feasible, transporting surface water from flood areas (or the ocean) to drought areas faces many challenges including water rights, property rights, environmental impacts, and more. Then there's the...

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####   Can a drought be relieved by bringing in water from other regions of the country that have excess water?

Any large-scale projects for mitigating drought in the U.S. would fall under the direction of the Bureau of Reclamation , which is the federal agency tasked with water management. While technically feasible, transporting surface water from flood areas (or the ocean) to drought areas faces many challenges including water rights, property rights, environmental impacts, and more. Then there's the...

Learn More

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####                 How can I find the HUC (Hydrologic Unit Code) for a stream? How can I find the name/location of a stream using the HUC?              

Hydrologic Units (HUs) represent the area of the landscape that drains to a portion of the stream network. Each drainage has a unique Hydrologic Unit Code (HUC). The most current national HU dataset is the Watershed Boundary Dataset (WBD) . HUCs from other sources might be out of date or differ from the WBD standards. The WBD includes six required levels of nested HU polygons (2- to 12-digit), two...

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####   How can I find the HUC (Hydrologic Unit Code) for a stream? How can I find the name/location of a stream using the HUC?

Hydrologic Units (HUs) represent the area of the landscape that drains to a portion of the stream network. Each drainage has a unique Hydrologic Unit Code (HUC). The most current national HU dataset is the Watershed Boundary Dataset (WBD) . HUCs from other sources might be out of date or differ from the WBD standards. The WBD includes six required levels of nested HU polygons (2- to 12-digit), two...

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####                 Can the USGS install a streamgage at my location?              

The USGS can install a streamgage almost anywhere, but in most cases we do not choose when and where to do that. We typically install and operate streamgages where other entities ask and reimburse us to do so. We operate streamgages for entities such as cities, towns, counties, state agencies, and other federal agencies to assist with their missions and to provide data for general public use...

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####   Can the USGS install a streamgage at my location?

The USGS can install a streamgage almost anywhere, but in most cases we do not choose when and where to do that. We typically install and operate streamgages where other entities ask and reimburse us to do so. We operate streamgages for entities such as cities, towns, counties, state agencies, and other federal agencies to assist with their missions and to provide data for general public use...

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####                 Where can I get watershed maps?              

Use The National Map Viewer to display or create watershed maps with the National Watershed Boundary Dataset . Watersheds are shown as Hydrologic Units, each one with a unique Hydrologic Unit Code (HUC). Go to The National Map Viewer (it might take a minute to fully load). In the green bar above the map, click on the Layers icon, which looks like a stack of paper. Click on the box beside...

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####   Where can I get watershed maps?

Use The National Map Viewer to display or create watershed maps with the National Watershed Boundary Dataset . Watersheds are shown as Hydrologic Units, each one with a unique Hydrologic Unit Code (HUC). Go to The National Map Viewer (it might take a minute to fully load). In the green bar above the map, click on the Layers icon, which looks like a stack of paper. Click on the box beside...

Learn More

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####                 Does the USGS provide precipitation data?              

NOAA is the federal agency tasked with collecting climate-grade precipitation data for the nation. Their rain gauges are usually located at manned sites where a local observer checks readings daily and performs regular maintenance. The USGS collects precipitation data at about 3,400 locations around the country, mostly where we already have streamgages (so at roughly a quarter of our streamgages)...

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####   Does the USGS provide precipitation data?

NOAA is the federal agency tasked with collecting climate-grade precipitation data for the nation. Their rain gauges are usually located at manned sites where a local observer checks readings daily and performs regular maintenance. The USGS collects precipitation data at about 3,400 locations around the country, mostly where we already have streamgages (so at roughly a quarter of our streamgages)...

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####                 Where can I get USGS water quality (water chemistry) data for surface water and/or groundwater?              

Water quality data is freely available through the USGS National Water Information System (NWIS)  and the Water Quality Portal (data from multiple agencies, including the USGS). Sometimes these data are hard to understand, so you can also contact the USGS Water Science Center for the state in question to request data and reports from studies that might have been conducted on water quality. The...

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####   Where can I get USGS water quality (water chemistry) data for surface water and/or groundwater?

Water quality data is freely available through the USGS National Water Information System (NWIS)  and the Water Quality Portal (data from multiple agencies, including the USGS). Sometimes these data are hard to understand, so you can also contact the USGS Water Science Center for the state in question to request data and reports from studies that might have been conducted on water quality. The...

Learn More

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####                 How does an earthquake affect groundwater levels and water quality in wells?              

Groundwater levels in wells can oscillate up and down when seismic waves pass. The water level might remain higher or lower for a period of time after the seismic waves end, but sometimes a long-term offset of groundwater levels follows an earthquake. The largest recorded earthquake-induced offset in a well is a one meter rise. Water quality can also be affected by earthquakes, typically in...

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####   How does an earthquake affect groundwater levels and water quality in wells?

Groundwater levels in wells can oscillate up and down when seismic waves pass. The water level might remain higher or lower for a period of time after the seismic waves end, but sometimes a long-term offset of groundwater levels follows an earthquake. The largest recorded earthquake-induced offset in a well is a one meter rise. Water quality can also be affected by earthquakes, typically in...

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####                 What sources were used to produce the National Hydrography Dataset (NHD)?              

The National Hydrography Dataset (NHD) is a combination of USGS hydrologic digital line graph (DLG) files and Environmental Protection Agency (EPA) reach files, version 3.0 (RF3). U.S. Forest Service Cartographic Feature Files (CFF) and USGS Tagged Vector Hydro (TVH) captured from 7.5-minute printed maps were also used. Some states also contributed their own stream layer data to the compilation of...

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####   What sources were used to produce the National Hydrography Dataset (NHD)?

The National Hydrography Dataset (NHD) is a combination of USGS hydrologic digital line graph (DLG) files and Environmental Protection Agency (EPA) reach files, version 3.0 (RF3). U.S. Forest Service Cartographic Feature Files (CFF) and USGS Tagged Vector Hydro (TVH) captured from 7.5-minute printed maps were also used. Some states also contributed their own stream layer data to the compilation of...

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####                 What is the positional accuracy of the National Hydrography Dataset (NHD)?              

Original hydrographic data were compiled to meet National Map Accuracy standards . These standards have been maintained in the process of creating the NHD. At 1:100,000 scale, ninety percent of well-defined features are within 167 feet (0.02 inches at map scale) of their true geographic position. When higher resolution data are created and submitted, the positional accuracy may vary due to...

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####   What is the positional accuracy of the National Hydrography Dataset (NHD)?

Original hydrographic data were compiled to meet National Map Accuracy standards . These standards have been maintained in the process of creating the NHD. At 1:100,000 scale, ninety percent of well-defined features are within 167 feet (0.02 inches at map scale) of their true geographic position. When higher resolution data are created and submitted, the positional accuracy may vary due to...

Learn More

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####                 What is the National Hydrography Dataset (NHD)?              

The National Hydrography Dataset (NHD) is a digital vector dataset used by Geographic Information Systems (GIS) to define the spatial locations of surface waters and is designed to provide comprehensive coverage of surface water data for the U.S. The NHD contains features such as lakes, ponds, streams, rivers, canals, dams, and stream gages in a relational database model system. These data are...

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####   What is the National Hydrography Dataset (NHD)?

The National Hydrography Dataset (NHD) is a digital vector dataset used by Geographic Information Systems (GIS) to define the spatial locations of surface waters and is designed to provide comprehensive coverage of surface water data for the U.S. The NHD contains features such as lakes, ponds, streams, rivers, canals, dams, and stream gages in a relational database model system. These data are...

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