20250328 10315100 1.0 ISO19115_3 150000000 5000 TRUE <div style='text-align: left;'> This dataset is a depiction of the estimated background levels (25 centile of median measurements) by ecoregion for the collection of water samples collected across the United States from 2000-2023 from the Water Quality Portal (WQP), which integrates publicly available water quality data from the USGS National Water Information System (NWIS) and the EPA Water Quality Exchange (WQX) Data Warehouse. These water quality data records are provided by many federal, state, and tribal organizations and other partners. Because these data are from secondary sources, the U.S. EPA cannot ensure that the information is accurate, current, or complete. Therefore, users should verify the data from the original sources before drawing site specific conclusions. Ecoregions are areas that share similar ecosystems and environmental resources. They provide a framework for researching, assessing, managing, and monitoring ecosystems. These regions are essential for coordinating ecosystem management among federal and state agencies, as well as NGOs, that oversee various resources in the same areas. The mapping of ecoregions is based on analyzing biotic and abiotic factors such as geology, climate, vegetation, and land use, with the significance of each factor varying by region. A hierarchical system uses Roman numerals to categorize these regions: Level I includes 15 broad regions in North America, Level II has 50, Level III divides the continental U.S. into 105 regions, and Level IV offers further subdivisions. Detailed methods for defining these ecoregions can be found in works by Omernik and others.   Hunt, D.T.E. and A.L. Wilson. 1986. The Chemical Analysis of Water: General Principles and Techniques. 2nd ed. Royal Society of Chemistry, London, England. Olson, J.R., Hawkins, C.P., 2012. Predicting natural base‐flow stream water chemistry in the western United States. Water Resources Research, 48(2). doi: https://doi.org/10.1029/2011WR011088 Omernik, J. M.; Griffith, G. E., 2014. Ecoregions of the conterminous United States: evolution of a hierarchical spatial framework. Environmental. Management. 54 (6), 1249−1266. doi: https://doi.org/10.1007/s00267-014-0364-1 Stumm, Werner (1981). Aquatic chemistry: an introduction emphasizing chemical equilibria in natural waters. New York: Wiley. ISBN 0-471-04831-3. OCLC 6889980. U.S. Environmental Protection Agency. 2013. Level III and IV ecoregions of the continental United States. U.S. EPA, National Health and Environmental Effects Research Laboratory, Corvallis, Oregon, Map scale 1:3,000,000. Available online at: https://www.epa.gov/wed/pages/ecoregions/level_iii_iv.htm. USEPA. 1976. Quality Criteria for Water. EPA 440-9-76-023. https://www.epa.gov/sites/default/files/2018-10/documents/quality-criteria-water-1976.pdf. Water Quality Portal. Washington (DC): National Water Quality Monitoring Council, United States Geological Survey (USGS), Environmental Protection Agency (EPA); 2021. https://doi.org/10.5066/P9QRKUVJ.   </div> Water Quality Estimated Background by Level III Ecoregion 2025-04-01T00:00:00 -179.044168 -55.695548 73.882358 2.808075 WaterQualityEstimatedBackgroundLevel IIIEcoregionFreshwaterExplorerRiverStreamUSEPANationalStateAlkalinityAmmoniaCalciumChlorphyll AChlorideConductivityOrganic CarbonpHPhosphorusSulfateTotal NitrogenWhartonCormier Water Quality Estimated Background by Level III Ecoregion Authors: Wharton, C., Cormier, S. M. <div style='text-align: Left; font-size: 12pt;'> <div> <div> Freshwater Explorer Data Disclaimer This data is intended for exploratory and discussion purposes. Although statutory provisions and U.S. Environmental Protection Agency (EPA) regulations contain legally binding requirements, these data and related information are not regulatory nor do they change or substitute for any provisions or regulations. The information does not substitute for the Clean Water Act, a National Pollutant Discharge Elimination System permit, or EPA or state regulations applicable to permits; nor is this material a permit or regulation itself. Thus, it does not impose legally binding requirements on EPA, states, tribes, or the regulatory community. This information does not confer legal rights or impose legal obligations on any member of the public. Mention of any trade names, products, or services is not and should not be interpreted as conveying official EPA approval, endorsement, or recommendation. While EPA has used its best efforts to include complete and accurate information in this system, EPA cannot be held responsible for errors or omissions and is not liable for any direct, indirect, or consequential damages resulting from using this secondary information. Some potential sources of error have been assessed by the U.S. EPA resulting in the removal of some samples from the original data sets. However, all sources of potential error cannot be eliminated from the measured data reported in the Freshwater Explorer or the data used to develop predictive models. Therefore, the U.S. EPA cannot fully ensure either the original data or the values calculated from them. Conclusions and assessments drawn from the use of the Freshwater Explorer are the responsibility of the user.   Please check sources, scale, accuracy, dates, and other available information. Please confirm that you are using the most recent copy of both data and metadata. Reliance on the information contained in this system by any party cannot be used as a defense in any administrative or judicial proceeding.   This dataset may be revised periodically. EPA can revise this dataset without public notice to reflect changes in EPA policy, guidance, and advancements in the field of biological assessments. EPA welcomes public input on this document at any time. Send comments to FreshwaterExplorer@epa.gov, National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr, Cincinnati, OH 45268. </div> </div> </div> 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 20250328 United States Environmental Protection Agency