Listed below are publications giving details about ecoregions, which are areas of general similarity in the type, quality, and quantity of environmental resources.  For additional information and links to downloadable ecoregion maps and datasets, see our Ecoregions page.

Omernik, J., G. Griffith, R. Hughes, J. Glover, AND M. Weber. How Misapplication of the Hydrologic Unit Framework Diminishes the Meaning of Watersheds. ENVIRONMENTAL MANAGEMENT. Springer-Verlag, New York, NY, 60(1):1-11, (2017). ftp://newftp.epa.gov/EPADataCommons/ORD/Ecoregions/pubs/HUCsWatersheds_Omernik-et-al_2017.pdf

Omernik, J., S. Paulsen, G. Griffith, and M. Weber. 2016. Regional patterns of total nitrogen concentrations in the National Rivers and Streams Assessment. Journal of Soil and Water Conservation 71(3):167-181. ftp://newftp.epa.gov/EPADataCommons/ORD/Ecoregions/pubs/NitrogenPatterns_Omernik-2016_JSWC-fnl.pdf

Griffith, G.E., J.M. Omernik, , D.W. Smith, T.D. Cook, E. Tallyn, Moseley, K. and C.B. Johnson. 2016. Ecoregions of California (2 sided color poster with map, descriptive text, and photographs). U.S. Geological Survey Open-File Report 2016-1021, map scale 1:1,100,000, http://dx.doi.org/10.3133/ofr20161021.

Omernik, J.M., and G.E. Griffith. 2014. Ecoregions of the conterminous United States: evolution of a hierarchical spatial framework. Environmental Management 54(6):1249-1266, http://dx.doi.org/10.1007/s00267-014-0364-1.

Griffith, G.E., J.M. Omernik, C.B. Johnson, and D.S. Turner. 2014. Ecoregions of Arizona (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey Open-File Report 2014-1141, map scale 1:1,325,000, http://dx.doi.org/10.3133/ofr20141141.

Wiken, E., F. Jiménez Nava, and G. Griffith. 2011. North American Terrestrial Ecoregions—Level III. Commission for Environmental Cooperation, Montreal, Canada. 149p.

Bryce, S.A., G.E. Griffith, J.M. Omernik, G. Edinger, S. Indrick, O. Vargas, and D. Carlson. 2010. Ecoregions of New York (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,250,000.

Griffith, G.E., J.M. Omernik, S.A. Bryce, J. Royte, W.D. Hoar, J.W. Homer, D. Keirstead, K.J. Metzler, and G. Hellyer. 2009. Ecoregions of New England (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,325,000.

Griffith, G.E., S.B. Bryce, J.M. Omernik, and A. Rogers. 2007. Ecoregions of Texas. Texas Commission on Environmental Quality. Austin, TX. 125p.

Woods, A.J., J.M. Omernik, and B.C Moran. 2007. Level III and IV Ecoregions of New Jersey. U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Western Ecology Division, Corvallis, Oregon. 19p.

Chapman, S.S., G.E. Griffith, J.M. Omernik, A.B. Price, J. Freeouf, and D.L. Schrupp. 2006. Ecoregions of Colorado. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,200,000.

Daigle, J.J., G.E. Griffith, J.M. Omernik, P.L. Faulkner, R.P. McCulloh, L.R. Handley, L.M. Smith, and S.S. Chapman. 2006. Ecoregions of Louisiana. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,000,000.

Griffith, G.E., J.M. Omernik, M.M. McGraw, G.Z. Jacobi, C.M. Canavan, T.S. Schrader, D. Mercer, R. Hill, and B.C. Moran. 2006. Ecoregions of New Mexico (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,400,000.

Woods, A.J., J.M. Omernik, C.L. Pederson, and B.C Moran. 2006. Level III and IV Ecoregions of Illinois. Corvallis, Oregon, U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Western Ecology Division, U.S. EPA Report, EPA/600/R-06/104, 45 p.

Woods, A.J., J.M. Omernik, D.R. Butler, J.G. Ford, J.E. Henley, B.W. Hoagland, D.S. Arndt, and B.C. Moran. 2005. Ecoregions of Oklahoma. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,250,000.

Chapman, S.S., G.E. Griffith, J.M. Omernik, J.A. Comstock, M.C. Beiser, and D. Johnson. 2004. Ecoregions of Mississippi. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,000,000.

Chapman, S.S., B.A. Kleiss, J.M. Omernik, T.L. Foti, and E.O. Murray. 2004. Ecoregions of the Mississippi Alluvial Plain. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,150,000.

Chapman, S.S., S.A. Bryce, J.M. Omernik, D.G. Despain, J. ZumBerge, and M. Conrad. 2004. Ecoregions of Wyoming. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,400,000.

Gallant, A.L., T.R. Loveland, T.L. Sohl, and D.E. Napton. 2004. Using an ecoregion framework to analyze landcover and land-use dynamics. Environmental Management 34(Supplement 1):s89-s110.

Griffith, G.E., S.A. Bryce, J.M. Omernik, J.A. Comstock, A.C. Rogers, B. Harrison, S.L. Hatch, and D. Bezanson. 2004. Ecoregions of Texas. (2 sided color poster with map, descriptive text, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:2,500,000.

Omernik, J.M. 2004. Perspectives on the nature and definition of ecological regions. Environmental Management 34(Supplement 1):s27-s38.

Stoddard, J.L. 2004. Use of ecological regions in aquatic assessments of ecological condition. Environmental Management 34(Supplement 1):s61-s70.

Woods, A.J., T.L. Foti, Chapman, S.S., J.M. Omernik, J. Wise, E.O. Murray, W.L. Prior, J. Pagan, J.A. Comstock, and M. Radford. 2004. Ecoregions of Arkansas. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,000,000.

Bryce, S.A., A.J. Woods, J.D. Morefield, J.M. Omernik, T.R. McKay, G.K. Brackley, R.K. Hall, D.K. Higgins, D.C. McMorran, K.E. Vargas, E.B. Petersen, D.C. Zamudio, and J.A. Comstock. 2003. Ecoregions of Nevada. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,350,000.

Omernik, J.M. 2003. The misuse of hydrologic unit maps for extrapolation, reporting, and ecosystem management. Journal of the American Water Resources Association 39(3): 563-573.

Shirazi, M.A., C.B. Johnson, J.M. Omernik, D. White, P.K. Haggerty, and G.E. Griffith. 2003. Quantitative soil descriptions for ecoregions of the United States. Journal of Environmental Quality 32:550-561.

Thorson, T.D., S.A. Bryce, D.A. Lammers, A.J. Woods, J.M. Omernik, J. Kagan, D.E. Pater, and J.A. Comstock. 2003. Ecoregions of Oregon. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,500,000.

Chapman, S.S., J.M. Omernik, G.E. Griffith, W.A. Schroeder, T.A. Nigh, and T.F. Wilton. 2002. Ecoregions of Iowa and Missouri. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,800,000.

Griffith, G.E., J.M. Omernik, J.A. Comstock, M.P. Shafale, W.H. McNab, D.R. Lenat, J.B. Glover, and V.B. Shelburne. 2002. Ecoregions of North Carolina and South Carolina. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,500,000.

McGrath, C.L., A.J. Woods, J.M. Omernik, S.A. Bryce, M. Edmondson, J.A. Nesser, J. Shelden, R.C. Crawford, J.A. Comstock, and M.D. Plocher. 2002. Ecoregions of Idaho. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,350,000.

Woods, A.J., J.M. Omernik, W.H. Martin, G.J. Pond, W.M. Andrews, S.M. Call, J.A. Comstock, and D.D. Taylor. 2002. Ecoregions of Kentucky. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,000,000.

Chapman, S.S., J.M. Omernik, J.A. Freeouf, D.G. Huggins, J.R. McCauley, C.C. Freeman, G. Steinauer, R.T. Angelo, and R.L. Schlepp. 2001. Ecoregions of Nebraska and Kansas. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,950,000.

Griffith, G.E., J.M. Omernik, J.A. Comstock, S. Lawrence, G. Martin, A. Goddard, V.J. Hulcher, and T. Foster. 2001. Ecoregions of Alabama and Georgia. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,700,000.

Griffith, G., J. Omernik, T. Foster, and J. Comstock. 2001. Ecoregions of Georgia. U.S. EPA, National Health and Environmental Effects Research Laboratory, Corvallis, OR. 48p.

McMahon, G., S.M. Gregonis, S.W. Waltman, J.M. Omernik, T.D. Thorson, J.A. Freeouf, A.H. Rorick, and J.E. Keys. 2001. Developing a spatial framework of common ecological regions for the conterminous United States. Environmental Management 28(3):293-316.

Woods, A.J., D.A. Lammers, S.A. Bryce, J.M. Omernik, R.L. Denton, M. Domeier, and J.A. Comstock. 2001. Ecoregions of Utah. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,175,000.

Omernik, J.M., S.S. Chapman, R.A. Lillie, and R.T. Dumke. 2000. Ecoregions of Wisconsin. Transactions of the Wisconsin Academy of Science, Arts and Letters 88(2000):77-103.

Bryce, S.A., D.P. Larsen, R.M. Hughes, and P.R. Kaufmann. 1999. Assessing relative risks to aquatic ecosystems: a mid-Appalachian case study. Journal of the American Water Resources Association 35(1):23-36.

Bryce, S.A., J.M. Omernik, and D.P. Larsen. 1999. Ecoregions: a geographic framework to guide risk characterization and ecosystem management. Environmental Practice 1(3):141-155.

Griffith, G.E., J.M. Omernik, and A.J. Woods. 1999. Ecoregions, watersheds, basins, and HUCs: How state and federal agencies frame water quality. Journal of Soil and Water Conservation 54(4):666-677.

Woods, A.J., J.M. Omernik, J.A. Nesser, J. Shelden, and S.H. Azevedo. 1999. Ecoregions of Montana. (2 sided, 2 sheet color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,500,000.

Bryce, S.A., J.M. Omernik, D.E. Pater, M. Ulmer, J. Schaar, J. Freeouf, R. Johnson, P. Kuck, and S.H. Azevedo. 1998. Ecoregions of North Dakota and South Dakota. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,500,000.

Griffith, G.E., J.M. Omernik, and S.H. Azevedo. 1998. Ecoregions of Tennessee. (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:940,000.

Pater, D.E., S.A. Bryce, T.D. Thorson, J. Kagan, C. Chappell, J.M. Omernik, S.H. Azevedo, and A. J. Woods. 1998. Ecoregions of Western Washington and Oregon (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,350,000.

Woods, A.J., J.M. Omernik, C.S. Brockman, T.D. Gerber, W.D. Hosteter, and S.H. Azevedo. 1998. Ecoregions of Indiana and Ohio (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:500,000.

Commission for Environmental Cooperation. 1997. Ecological regions of North America: toward a common perspective. Commission for Environmental Cooperation, Montreal, Quebec, Canada. 71pp.

Clarke, S.E. and S.A. Bryce. 1997. Hierarchical subdivisions of the Columbia Plateau & Blue Mountains ecoregions, Oregon & Washington. General Technical Report PNW-GTR-395. U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, Portland, OR. 114p.

Griffith, G. E., J. M. Omernik, and S. H. Azevedo. 1997. Ecoregions of Tennessee. EPA/600/R-97/022. U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Corvallis, OR. 51p.

Omernik, J.M. and R.G. Bailey 1997. Distinguishing between watersheds and ecoregions. Journal of the American Water Resources Association 33(5):1-15.

Bryce, S. A. and S. E. Clarke. 1996. Landscape-level ecological regions: linking state-level ecoregion frameworks with stream habitat classifications. Environmental Management 20(3):297-311.

Woods, A.J., J.M. Omernik, D.D. Brown, and C.W. Kiilsgaard. 1996. Level III and IV ecoregions of Pennsylvania and the Blue Ridge Mountains, the Ridge and Valley, and Central Appalachians of Virginia, West Virginia, and Maryland. EPA/600/R-96/077. U.S. EPA National Health and Environmental Effects Research Laboratory, Corvallis, OR. 50p.

Woods, A.J. and J.M. Omernik. 1996. Ecoregions of Pennsylvania. The Pennsylvania Geographer 34(2):2-37.

Gallant, A.L., E.F. Binnian, J.M. Omernik, and M.B. Shasby. 1995. Ecoregions of Alaska. U.S. Geological Survey Professional Paper 1567. U.S. Government Printing Office, Washington D.C.

Omernik, J.M. 1995. Ecoregions: a spatial framework for environmental management. In: Biological Assessment and Criteria: Tools for Water Resource Planning and Decision Making, W. Davis and T.P. Simon (eds.). Lewis Publishing, Boca Raton, FL. pp. 49-62.

Omernik, J. M. 1995. Ecoregions: a framework for managing ecosystems. The George Wright Forum 12(1):35-50.

Griffith, G.E., J.M. Omernik, S.M. Pierson, and C.W. Kiilsgaard. 1994. Massachusetts ecological regions project. EPA/600/A-94/111. U.S. EPA, Environmental Research Laboratory, Corvallis, OR. 58p.

Griffith, G.E., J.M. Omernik, T.F. Wilton, and S.M. Pierson. 1994. Ecoregions and subregions of Iowa: a framework for water quality assessment and management. The Journal of the Iowa Academy of Science 101(1):5-13.

Griffith, G.E., J.M. Omernik, C.M. Rohm, and S.M. Pierson. 1994. Florida regionalization project. EPA/600/Q-95/002. U.S. EPA, Environmental Research Laboratory, Corvallis, OR. 83p.

Hughes, R.M. S.A. Heiskary, W.J. Matthews, and C.O. Yoder. 1994. Use of ecoregions in biological monitoring. In: Biological Monitoring of Aquatic Systems. S.L. Loeb and A. Spacie (eds.). Lewis Publishers, Boca Raton, FL. pp.125-151.

Clarke, S.E., D. White, and A.L. Schaedel. 1991. Oregon, USA, ecological regions and subregions for water quality management. Environmental Management 15(6):847-856.

Omernik, J.M. and G.E. Griffith. 1991. Ecological regions vs. hydrologic units: frameworks for managing water quality. Journal of Soil and Water Conservation 46(5):334-340.

U. S. Environmental Protection Agency Science Advisory Board. 1991. Evaluation of the ecoregion concept. Report of the Ecoregions Subcommittee of the Ecological Processes and Effects Committee. EPA-SAB-EPEC-91-003, Washington, DC. 25p.

Hughes, R.M., T.R. Whittier, C.M. Rohm, and D.P. Larsen. 1990. A regional framework for establishing recovery criteria. Environmental Management 14(5):673-683.

Omernik, J.M. and A.L. Gallant. 1990. Defining regions for evaluating environmental resources. In: Proceedings of the Global Natural Resource Monitoring and Assessment Symposium, Preparing for the 21st. Century; Venice, Italy, September 24-30, 1989. pp. 936-947.

Gallant, A.L., T.R. Whittier, D.P. Larsen, J.M. Omernik, and R.M. Hughes. 1989. Regionalization as a tool for managing environmental resources. EPA/600/3-89/060. U.S. EPA, Environmental Research Laboratory, Corvallis, OR, 152p.

Heiskary, S.A. and B.C. Wilson. 1989. The regional nature of lake quality across Minnesota: an analysis for improving resource management. Journal of the Minnesota Academy of Science 55(1):71-77.

Hughes, R.M. 1989. What can biological monitoring tell us about the environmental health of aquatic ecosystems? In: Proceedings of an International Symposium; Design of Water Quality Information Systems. R.C. Ward, J.C Loftis and G.B. McBride (eds.). Fort Collins, CO. pp. 447-460.

Hughes, R.M. 1989. Ecoregional biological criteria. In: Proceedings of an EPA Conference, Water Quality Standards for the 21st Century, Dallas, TX. 4p.

Hughes, R.M. and D.P. Larsen. 1988. Ecoregions: an approach to surface water protection. Journal of the Water Pollution Control Federation 60:486-493.

Larsen, D.P., D.R. Dudley, and R.M. Hughes. 1988. A regional approach to assess attainable water quality: An Ohio case study. Journal of Soil and Water Conservation 43:171-176.

Omernik, J.M. and A.L. Gallant. 1988. Ecoregions of the Upper Midwest States. EPA/600/3-88/037. U.S. EPA, Environmental Research Laboratory, Corvallis, OR. 56p.

Whittier, T.R., R.M. Hughes, and D.P. Larsen. 1988. Correspondence between ecoregions and spatial patterns in stream ecosystems in Oregon. Canadian Journal of Fisheries and Aquatic Sciences 45:1264-1278.

Heiskary, S.A., B.C. Wilson, and D.P. Larsen. 1987. Analysis of regional patterns in lake water quality: using ecoregions for lake management in Minnesota. Lake and Reservoir Management 3:337-344.

Hughes, R.M., E. Rexstad, and C.E. Bond. 1987. The relationship of aquatic ecoregions, river basins, and physiographic provinces to the ichthyogeographic regions of Oregon. Copeia 2:423-432.

Omernik, J.M. 1987. Ecoregions of the conterminous United States. Annals of the Association of American Geographers 77:118-125.

Omernik, J.M. 1987. Ecoregions of the Northeast States. Map (scale 1:2,500,000). EPA/600/D-87/313. Environmental Protection Agency, Environmental Research Laboratory, Corvallis, OR.

Omernik, J.M. and A.L. Gallant. 1987. Ecoregions of the Southwest States. Map (scale 1:2,500,000. EPA/600/D-87/316. U.S. EPA, Environmental Research Laboratory, Corvallis, OR.

Omernik, J.M. and A.L. Gallant. 1987. Ecoregions of the West Central States. Map (scale 1:2,500,000). EPA/600/D-87/317. U.S. EPA, Environmental Research Laboratory, Corvallis, OR.

Rohm, C.M., J.W. Giese, and C.C. Bennett. 1987. Evaluation of an aquatic ecoregion classification of streams in Arkansas. Journal of Freshwater Ecology 4(1): 127-140.

Whittier, T.R., D.P. Larsen, R.M. Hughes, C.M. Rohm, A.L. Gallant, and J.M. Omernik. 1987. The Ohio stream regionalization project: a compendium of results. EPA/600/3/-87/025. U.S. EPA, Environmental Research Laboratory, Corvallis, OR. 66p.

Hughes, R.M., D.P. Larsen, and J.M. Omernik. 1986. Regional reference sites: A method for assessing stream potentials. Environmental Management 10:629-635.

Larsen, D.P., R.M. Hughes, J.M. Omernik, D.R. Dudley, C.M. Rohm, T.R. Whittier, A.J. Kinney, and A.L. Gallant. 1986. Correspondence between spatial patterns in fish assemblages in Ohio streams and aquatic ecoregions. Environmental Management 10:815-828.

Omernik, J.M. and A.L. Gallant. 1986. Ecoregions of the Pacific Northwest. EPA/600/3-86/033. U.S. EPA, Environmental Research Laboratory, Corvallis, OR. 39 p.

Hughes, R.M., J.H. Gakstatter, M.A. Shirazi, and J.M. Omernik. 1982. An approach for determining biological integrity in flowing waters. In: In-Place Resource Inventories: Principles and Practices, Proceedings of a National Workshop, August 9-14, 1981, Orono, Maine. T.B. Brann, L.O. House, and H.G. Lund, (eds.). Society of American Foresters, Bethesda, MD. pp. 877-888.

Omernik, J.M., M.A. Shirazi, and R.M. Hughes. 1982. A synoptic approach for regionalizing aquatic ecosystems. In: In-Place Resource Inventories: Principles and Practices, Proceedings of a National Workshop, August 9-14, 1981, Orono, Maine. T.B. Brann, L.O. House, and H.G. Lund, (eds.). Society of American Foresters, Bethesda, MD. pp. 199-218