Water
Where can I find flood maps?
What is the difference between a confined and unconfined aquifer?
Does the use of pesticides affect our Nation's water quality?
How much natural water is there?
The USGS monitors and studies a wide range of water resources and water conditions, including streamflow, groundwater, water quality, and water use and availability.
Where can I get watershed maps? 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 "Watershed...
Does the USGS provide precipitation data? 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)...
Where can I get USGS water quality (water chemistry) data for surface water and/or groundwater? 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...
How does an earthquake affect groundwater levels and water quality in wells? 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...
What sources were used to produce the National Hydrography Dataset (NHD)? 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...
What is the positional accuracy of the National Hydrography Dataset (NHD)? 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...
What is the National Hydrography Dataset (NHD)? 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...
In what scale are the data in the National Hydrography Dataset (NHD)? In what scale are the data in the National Hydrography Dataset (NHD)?
Scales for data in the National Hydrography Dataset: Conterminous United States, Hawaii, and the Virgin Islands, medium resolution - 1:100,000-scale Conterminous United States, Hawaii, and the Virgin Islands, high resolution - 1:24,000-scale Puerto Rico - 1:20,000-scale Alaska - 1:63,360-scale Users are encouraged to work with their state's principal steward to produce and submit data at higher...
What formats are available for hydrography data products in The National Map? What formats are available for hydrography data products in The National Map?
Depending on the product type, hydrography data are offered in Esri File Geodatabase 10.1, Shapefile or GeoPackage formats. National Hydrography Dataset (NHD) data is available as national extracts, state extracts, 4-digit sub-regions, 8-digit sub-basins, or in a specified extent from The National Map Downloader. A national extent of medium and high resolution NHD data in File Geodatabase format...
How do I download hydrography data products? How do I download hydrography data products?
Download USGS hydrography data (datasets representing U.S. surface water for mapping and modeling applications) using The National Map Downloader or using download links that are listed at Access National Hydrography Products. Learn more: The National Map: Hydrography Training Videos National Hydrography Dataset User Guide For streamflow data, see: Where can I get real-time and historical...
How much water is used by people in the United States? How much water is used by people in the United States?
Since 1950, the USGS has collected and analyzed water-use data for the United States and its Territories. That data is revised every 5 years. As of 2015, the United States uses 322 billion gallons of water per day (Bgal/day). The three largest water-use categories were irrigation (118 Bgal/day), thermoelectric power (133 Bgal/day), and public supply (39 Bgal/day), cumulatively accounting for 90...
What is the Earth's "water cycle?" What is the Earth's "water cycle?"
The water cycle, also known as the hydrologic cycle, describes where water is stored on Earth and how it moves. Water is stored in the atmosphere, on the land surface, and below the ground. It can be a liquid, a solid, or a gas. Liquid water can be fresh or saline (salty). Water moves between the places it is stored. It moves at large scales (through watersheds, the atmosphere, and below the Earth...