This dataset shows the temporal frequency and spatial extent of cyanobacteria cells in large, freshwater lakes and reservoirs across the continental United States derived from 300x300 meter MEdium Resolution Imaging Spectrometer (MERIS) satellite imagery from 2002-2012 and functionally similar Ocean and Land Colour Instrument (OLCI) satellite imagery from 2017-2021. This dataset was produced through a partnership with the National Oceanic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration (NASA), the United States Geological Survey (USGS), and the United States Environmental Protection Agency (USEPA). This cyanobacteria dataset was derived using the European Space Agency's (ESA) Envisat MERIS sensor and their Sentinel-3 OLCI sensor. MERIS and OLCI are nadir-pointing imaging spectrometers which measure the solar radiation reflected by the Earth in 15 and 21 spectral bands, respectively (visible through near-infrared). MERIS and OLCI imagery was used to identify long-wavelength spectral bands (from red through near-infrared portion of the spectrum) to locate algal blooms within freshwaters and estuaries of the continental United States. EnviroAtlas allows users to spatially explore this cyanobacteria data in the online interactive map viewer. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the continental United States. The dataset is available as downloadable data (https://oceancolor.gsfc.nasa.gov/CYAN/) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

This map displays predicted probability of a 12-digit Hydrologic Unit (HUC12) being at risk of violating the drinking water nitrate standard. Risk is defined as there being greater than a 50% chance of having a drinking water violation. Observed violations of the nitrate standard in public drinking water was used to make predictions across the conterminous United States. The data on nitrate violations comes from the EPA's Safe Drinking Water Information System (SDWIS) and the data used as predictor variables in the prediction models comes from EPA's StreamCat database. The original predictions were made at the National Hydrography Dataset (NHD) Catchment scale and summarized at the HUC12 scale and/or 300 m pixel scale. The maps show that 19% of the conterminous United States is at risk of groundwater sourced drinking violations, while 16% of the U.S. is at risk of nitrate violations from surface water sources. Regions with the highest risk of nitrate drinking violations from groundwater sources are found in the southwest, south central plains, parts of north west, mid-Atlantic. Surface water sourced nitrate violations have the greatest risk primarily in the southwest and south-central areas of the U.S. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

This map displays predicted probability of a 12-digit Hydrologic Unit (HUC12) being at risk of violating the drinking water nitrate standard. Risk is defined as there being greater than a 50% chance of having a drinking water violation. Observed violations of the nitrate standard in public drinking water was used to make predictions across the conterminous United States. The data on nitrate violations comes from the EPA's Safe Drinking Water Information System (SDWIS) and the data used as predictor variables in the prediction models comes from EPA's StreamCat database. The original predictions were made at the National Hydrography Dataset (NHD) Catchment scale and summarized at the HUC12 scale and/or 300 m pixel scale. The maps show that 19% of the conterminous United States is at risk of groundwater sourced drinking violations, while 16% of the U.S. is at risk of nitrate violations from surface water sources. Regions with the highest risk of nitrate drinking violations from groundwater sources are found in the southwest, south central plains, parts of north west, mid-Atlantic. Surface water sourced nitrate violations have the greatest risk primarily in the southwest and south-central areas of the U.S. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

This data layer represents all surface water features in the United States. This grid was created by combining water features identified in two sources, the Cropland Data Layer-National Land Cover Database (CDL-NLCD), and the National Hydrography Dataset (NHD Plus version 2.1). First, the surface water features were extracted from the 2011 CDL-NLCD. The CDL-NLCD, which was developed by the EnviroAtlas team, is a hybrid of the 2011 CDL produced by the National Agricultural Statistics Service (NASS) and the 2011 NLCD produced by the Multi-Resolution Land Characteristics Consortium. Features included are 'Open Water' (code 11), 'Woody Wetlands' (code 90) and 'Emergent Herbaceous Wetlands' (code 95).The second source used was the flowline and waterbody features as represented in the catseed grid from the NHD Plus version 2.1, downloaded June 18, 2013. The combination of these two datasets represents surface water and is referred to as the 'Water Mask.' This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas and the Watershed Index Online (WSIO). EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

This data layer represents all surface water features in the United States. This grid was created by combining water features identified in two sources, the Cropland Data Layer-National Land Cover Database (CDL-NLCD), and the National Hydrography Dataset (NHD Plus version 2.1). First, the surface water features were extracted from the 2011 CDL-NLCD. The CDL-NLCD, which was developed by the EnviroAtlas team, is a hybrid of the 2011 CDL produced by the National Agricultural Statistics Service (NASS) and the 2011 NLCD produced by the Multi-Resolution Land Characteristics Consortium. Features included are 'Open Water' (code 11), 'Woody Wetlands' (code 90) and 'Emergent Herbaceous Wetlands' (code 95).The second source used was the flowline and waterbody features as represented in the catseed grid from the NHD Plus version 2.1, downloaded June 18, 2013. The combination of these two datasets represents surface water and is referred to as the 'Water Mask.' This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas and the Watershed Index Online (WSIO). EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

Cyanobacteria Assessment Network (CyAN) is a multi-agency project among EPA, the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA), and the United States Geological Survey (USGS) to support the environmental management and public use of U.S. lakes and estuaries by providing a capability of detecting and quantifying cyanobacteria algal blooms. This effort has resulted in the production of satellite remote sensing products using the cyanobacteria index (CI) algorithm to estimate cyanobacteria concentrations (CI_cyano) in lakes across the contiguous United States (CONUS) and Alaska. The Merged S3 product combines Sentinel-3A and Sentinel-3B OLCI data.

This EnviroAtlas dataset is a summary of the National Dams Inventory data from 2009 survey. The file contains counts of inventoried dams by 12-digit hydrologic units codes (March 2011) and total maximum storage capacity in millions of gallons. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

This EnviroAtlas web service contains layers depicting NHD Version 2.1 Plus flowlines and waterbodies for the conterminous United States. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).