National Water-Quality Assessment (NAWQA): 1991-2012 Completed
National Water-Quality Assessment Project (NAWQA)
A leading source of scientific data and knowledge on the quality of our Nation’s water resources
Water-Quality Topics
Read about USGS water-quality research on a range of topics, from pesticides to PAHs, from radionuclides to redox
In 1991, Congress established the National Water-Quality Assessment (NAWQA) Project to address where, when, why, and how the Nation's water quality has changed, or is likely to change in the future, in response to human activities and natural factors. This page discusses the first two decadal cycles of NAWQA research from 1991 through 2012.
► Read below about the first two decades of NAWQA research:
- First decade - Baseline survey of water-quality conditions in 51 river basins and aquifers
- Second decade - Synthesis reports on major water quality topics of national priority
► Explore current NAWQA research
The NAWQA Project was designed to run in decadal cycles. From 1991-2001, the first decade, the NAWQA Project conducted interdisciplinary assessments and established a baseline understanding of water-quality conditions in 51 of the Nation's river basins and aquifers, referred to as Study Units. Descriptions of water-quality conditions in streams and groundwater were developed in more than 1,500 reports. Non-technical Summary Reports, written primarily for those interested or involved in resource management, conservation, regulation, and policymaking and listed below, were completed for each of the Study Units. Non-technical national summary reports on pesticides, nutrients, trace elements, and volatile organic compounds (VOCs) also were completed, in which water-quality conditions were compared to national standards and guidelines related to drinking water, protection of aquatic life, and nutrient enrichment.
NAWQA activities during the second decade (2002-2012) focused in large part on national and regional assessments. These assessments built on continued monitoring and assessments in 42 of the 51 Study Units completed in the first decade (USGS Fact Sheet 071-01). During the second decade, there was an emphasis on synthesizing the results of the Study Unit investigations on major water-quality issues:
- Pesticides
- Nutrients
- Volatile Organic Compounds (VOCs) in Groundwater
- Ecological Health of Streams
- Trace Elements
New studies during the second decade focused on water-quality topics of national priority.
- Principal Aquifers
- Public-Supply Wells and Factors that Affect Their Vulnerability to Contamination
- Domestic Supply Wells
- Agriculture and Water Quality
- Nutrients and Stream Ecosystems
- Mercury in Streams
► Additional information on these and other water-quality topics
NAWQA Study Units
NAWQA Study Units covered a variety of important hydrologic and ecological resources; critical sources of contaminants, including agricultural, urban, and natural sources; and a high percentage of population served by municipal water supply and irrigated agriculture. Study Unit boundaries frequently croseds State boundaries and usually encompassed more than 10,000 square kilometers (about 3,900 square miles).
The Study-Unit design used a rotational sampling scheme; therefore, sampling intensity varied year to year at the different sites. In general, about one-third of the Study Units were intensively investigated at any given time for 3-4 years, followed by low-intensity monitoring. Trends in water-quality conditions were assessed about every 10 years.
Summary reports are listed below for the individual Study Units assessed during the first decade (1991-2001). Publications for principle aquifer assessments are listed at Groundwater Quality in Principal Aquifers of the Nation, 1991–2010.
Study Unit Summary Reports
(Number refers to the study units map, above)
1 - Acadian-Pontchartrain Drainages (LA, MS)
2 - Albemarle-Pamlico Drainage Basin (NC, VA)
3 - Allegheny and Monongahela River Basins (MD, NY, PA, WV)
4 - Apalachicola-Chattahoochee-Flint River Basin (AL, FL, GA)
5 - Central Arizona Basins (AZ)
6 - Central Columbia Plateau (ID, WA)
7 - Central Nebraska Basins (NE)
8 - Connecticut, Housatonic and Thames River Basins (CT, MA, NH, NY, RI, VT)
9 - Cook Inlet Basin (AK)
10 - Delaware River Basin (PA, NY, NJ)
11 - Delmarva Peninsula (DE, MD, VA)
12 - Eastern Iowa Basins (IA, MN)
13 - Georgia-Florida Coastal Plain (GA, FL)
14 - Great and Little Miami River Basins (OH, IN)
15 - Great Salt Lake Basins (UT, ID, WY)
16 - Hudson River Basin (NY, CT, MA, NJ, VT)
17 - Island of Oahu (HI)
18 - Kanawha-New River Basins (WV, VA, NC)
19 - Lake Erie-Lake Saint Clair Drainages (IN, MI, OH, PA, NY)
20 - Long Island-New Jersey Coastal Drainages (NJ, NY)
21 - Lower Illinois River Basin (IL)
22 - Lower Susquehanna River Basin (MD, PA)
23 - Lower Tennessee River Basin (TN, AL, GA)
24 - Las Vegas Valley Area and the Carson and Truckee River Basins (NV, CA)
25 - Mississippi Embayment (AR, KY, LA, MS, MO, TN)
26 - Mobile River Basin (MS, AL, GA)
27 - New England Coastal Basins (ME, MA, NH, RI)
28 - Northern Rockies Intermontane Basins (ID, MT, WA)
29 - Ozark Plateaus (AR, KS, MO, OK)
30 - Potomac River Basin (DC, MD, PA, VA, WV)
31 - Puget Sound Basin (WA)
32 - Red River of the North Basin (MN, ND, SD)
33 - Rio Grande Valley (CO, NM, TX)
34 - Sacramento River Basin (CA)
35 - San Joaquin-Tulare Basins (CA)
36 - Santa Ana Basin (CA)
37 - Santee River Basin and Coastal Drainages (SC, NC)
38 - South-Central Texas (TX)
39 - South Platte River Basin (CO, NE, WY)
40 - Southern Florida (FL)
41 - Trinity River Basin (TX)
42 - Upper Colorado River Basin (CO, UT)
43 - Upper Illinois River Basin (IL, WI, IN)
44 - Upper Mississippi River Basin (MN, WI)
45 - Upper Snake River Basin (ID, MT, NV, UT, WY)
46 - Upper Tennessee River Basin (GA, KY, NC, SC, TN, VA)
47 - Western Lake Michigan Drainages (MI, WI)
48 - White River Basin (IN)
49 - Willamette Basin (OR)
50 - Yakima River Basin (WA)
51 - Yellowstone River Basin (MT, WY, ND)
Access the links below to learn more about water-quality science.
National Water-Quality Assessment (NAWQA)
NAWQA has produced more than 1,500 reports that describe how water-quality and ecological conditions; whether conditions are changing over time; and how natural features and human activities affect these conditions.
The most recent publications and selected national-scale reports are listed here. See the USGS Publications Warehouse for all NAWQA publications.
► Pubs Warehouse FAQs
Water Quality in the Delaware River Basin, Pennsylvania, New Jersey, New York, and Delaware, 1998-2001
Water quality in the Cook Inlet Basin Alaska, 1998-2001
Water quality in the Northern Rockies Intermontane basins, Idaho, Montana, and Washington, 1999-2001
Water quality in southern Florida: Florida, 1996-98
Water quality in the eastern Iowa basins, Iowa and Minnesota, 1996-98
Water quality in the Allegheny and Monongahela River basins, Pennsylvania, West Virginia, New York, and Maryland, 1996-98
Water quality in the upper Mississippi River basin, Minnesota, Wisconsin, South Dakota, Iowa, and North Dakota, 1995-98
Water quality in the central Arizona basins, Arizona, 1995-98
Water quality in the upper Tennessee River basin, Tennessee, North Carolina, Virginia, and Georgia 1994-98
Water quality in the upper Colorado River basin, Colorado, 1996-98
Water quality in south-central Texas, Texas, 1996–98
Water quality in the Santee River basin and coastal drainages, North and South Carolina, 1995-98
- Overview
In 1991, Congress established the National Water-Quality Assessment (NAWQA) Project to address where, when, why, and how the Nation's water quality has changed, or is likely to change in the future, in response to human activities and natural factors. This page discusses the first two decadal cycles of NAWQA research from 1991 through 2012.
► Read below about the first two decades of NAWQA research:
- First decade - Baseline survey of water-quality conditions in 51 river basins and aquifers
- Second decade - Synthesis reports on major water quality topics of national priority
► Explore current NAWQA research
The NAWQA Project was designed to run in decadal cycles. From 1991-2001, the first decade, the NAWQA Project conducted interdisciplinary assessments and established a baseline understanding of water-quality conditions in 51 of the Nation's river basins and aquifers, referred to as Study Units. Descriptions of water-quality conditions in streams and groundwater were developed in more than 1,500 reports. Non-technical Summary Reports, written primarily for those interested or involved in resource management, conservation, regulation, and policymaking and listed below, were completed for each of the Study Units. Non-technical national summary reports on pesticides, nutrients, trace elements, and volatile organic compounds (VOCs) also were completed, in which water-quality conditions were compared to national standards and guidelines related to drinking water, protection of aquatic life, and nutrient enrichment.NAWQA activities during the second decade (2002-2012) focused in large part on national and regional assessments. These assessments built on continued monitoring and assessments in 42 of the 51 Study Units completed in the first decade (USGS Fact Sheet 071-01). During the second decade, there was an emphasis on synthesizing the results of the Study Unit investigations on major water-quality issues:
- Pesticides
- Nutrients
- Volatile Organic Compounds (VOCs) in Groundwater
- Ecological Health of Streams
- Trace Elements
New studies during the second decade focused on water-quality topics of national priority.
- Principal Aquifers
- Public-Supply Wells and Factors that Affect Their Vulnerability to Contamination
- Domestic Supply Wells
- Agriculture and Water Quality
- Nutrients and Stream Ecosystems
- Mercury in Streams
► Additional information on these and other water-quality topics
Sources/Usage: Public Domain. View Media DetailsNAWQA Study Units
NAWQA Study Units covered a variety of important hydrologic and ecological resources; critical sources of contaminants, including agricultural, urban, and natural sources; and a high percentage of population served by municipal water supply and irrigated agriculture. Study Unit boundaries frequently croseds State boundaries and usually encompassed more than 10,000 square kilometers (about 3,900 square miles).
The Study-Unit design used a rotational sampling scheme; therefore, sampling intensity varied year to year at the different sites. In general, about one-third of the Study Units were intensively investigated at any given time for 3-4 years, followed by low-intensity monitoring. Trends in water-quality conditions were assessed about every 10 years.
Sources/Usage: Public Domain. View Media DetailsSummary reports are listed below for the individual Study Units assessed during the first decade (1991-2001). Publications for principle aquifer assessments are listed at Groundwater Quality in Principal Aquifers of the Nation, 1991–2010.
Study Unit Summary Reports
(Number refers to the study units map, above)
1 - Acadian-Pontchartrain Drainages (LA, MS)
2 - Albemarle-Pamlico Drainage Basin (NC, VA)
3 - Allegheny and Monongahela River Basins (MD, NY, PA, WV)
4 - Apalachicola-Chattahoochee-Flint River Basin (AL, FL, GA)
5 - Central Arizona Basins (AZ)
6 - Central Columbia Plateau (ID, WA)
7 - Central Nebraska Basins (NE)
8 - Connecticut, Housatonic and Thames River Basins (CT, MA, NH, NY, RI, VT)
9 - Cook Inlet Basin (AK)
10 - Delaware River Basin (PA, NY, NJ)
11 - Delmarva Peninsula (DE, MD, VA)
12 - Eastern Iowa Basins (IA, MN)
13 - Georgia-Florida Coastal Plain (GA, FL)
14 - Great and Little Miami River Basins (OH, IN)
15 - Great Salt Lake Basins (UT, ID, WY)
16 - Hudson River Basin (NY, CT, MA, NJ, VT)
17 - Island of Oahu (HI)
18 - Kanawha-New River Basins (WV, VA, NC)
19 - Lake Erie-Lake Saint Clair Drainages (IN, MI, OH, PA, NY)
20 - Long Island-New Jersey Coastal Drainages (NJ, NY)
21 - Lower Illinois River Basin (IL)
22 - Lower Susquehanna River Basin (MD, PA)
23 - Lower Tennessee River Basin (TN, AL, GA)
24 - Las Vegas Valley Area and the Carson and Truckee River Basins (NV, CA)
25 - Mississippi Embayment (AR, KY, LA, MS, MO, TN)
26 - Mobile River Basin (MS, AL, GA)
27 - New England Coastal Basins (ME, MA, NH, RI)
28 - Northern Rockies Intermontane Basins (ID, MT, WA)
29 - Ozark Plateaus (AR, KS, MO, OK)
30 - Potomac River Basin (DC, MD, PA, VA, WV)
31 - Puget Sound Basin (WA)
32 - Red River of the North Basin (MN, ND, SD)
33 - Rio Grande Valley (CO, NM, TX)
34 - Sacramento River Basin (CA)
35 - San Joaquin-Tulare Basins (CA)
36 - Santa Ana Basin (CA)
37 - Santee River Basin and Coastal Drainages (SC, NC)
38 - South-Central Texas (TX)
39 - South Platte River Basin (CO, NE, WY)
40 - Southern Florida (FL)
41 - Trinity River Basin (TX)
42 - Upper Colorado River Basin (CO, UT)
43 - Upper Illinois River Basin (IL, WI, IN)
44 - Upper Mississippi River Basin (MN, WI)
45 - Upper Snake River Basin (ID, MT, NV, UT, WY)
46 - Upper Tennessee River Basin (GA, KY, NC, SC, TN, VA)
47 - Western Lake Michigan Drainages (MI, WI)
48 - White River Basin (IN)
49 - Willamette Basin (OR)
50 - Yakima River Basin (WA)
51 - Yellowstone River Basin (MT, WY, ND)
- Science
Access the links below to learn more about water-quality science.
National Water-Quality Assessment (NAWQA)
Our surface water, groundwater, and aquatic ecosystems are priceless resources, used by people across the Nation for drinking, irrigation, industry, and recreation. The National Water-Quality Assessment (NAWQA) Project is a leading source of scientific data and knowledge for development of science-based policies and management strategies to improve and protect our water resources. - Publications
NAWQA has produced more than 1,500 reports that describe how water-quality and ecological conditions; whether conditions are changing over time; and how natural features and human activities affect these conditions.
The most recent publications and selected national-scale reports are listed here. See the USGS Publications Warehouse for all NAWQA publications.
► Pubs Warehouse FAQs
Filter Total Items: 63Water Quality in the Delaware River Basin, Pennsylvania, New Jersey, New York, and Delaware, 1998-2001
This report contains the major findings of a 1998-2001 assessment of water quality in the Delaware River Basin. It is one of a series of reports by the National Water-Quality Assessment (NAWQA) Program that present major findings in 51 major river basins and aquifer systems across the Nation.In these reports, water quality is discussed in terms of local, State, and regional issues. Conditions in aAuthorsJeffrey M. Fischer, Karen Riva-Murray, R. Edward Hickman, Douglas C. Chichester, Robin A. Brightbill, Kristin M. Romanok, Michael D. BilgerWater quality in the Cook Inlet Basin Alaska, 1998-2001
This report contains the major findings of a 1998?2001 assessment of water quality in the Cook Inlet Basin. It is one of a series of reports by the National Water-Quality Assessment (NAWQA) Program that present major findings in 51 major river basins and aquifer systems across the Nation. In these reports, water quality is discussed in terms of local, State, and regional issues. ConditionsAuthorsRoy L. Glass, Timothy P. Brabets, Steven A. Frenzel, Matthew S. Whitman, Robert T. OursoWater quality in the Northern Rockies Intermontane basins, Idaho, Montana, and Washington, 1999-2001
This report contains the major findings of a 1999–2001 assessment of water quality in the Northern Rockies Intermontane Basins. It is one of a series of reports by the National Water-Quality Assessment (NAWQA) Program that present major findings in 51 major river basins and aquifer systems across the Nation. In these reports, water quality is discussed in terms of local, State, and regional issuAuthorsGregory M. Clark, Rodney R. Caldwell, Terry R. Maret, Craig L. Bowers, DeAnn M. Dutton, Michael A. BecksmithWater quality in southern Florida: Florida, 1996-98
Major influences and findings for water quality and biology in southern Florida, including the Everglades, are described and illustrated. Samples were collected to determine total phosphorus, dissolved organic carbon, pesticides, mercury, nitrate, volatile organic carbon compounds, and radon-222. Water-management, agricultural, and land-use practices are discussed. Sixty-three species of fish in 2AuthorsBenjamin F. McPherson, Ronald L. Miller, Kim H. Haag, Anne BradnerWater quality in the eastern Iowa basins, Iowa and Minnesota, 1996-98
The water quality in rivers and streams and in selected aquifers in eastern Iowa and part of southern Minnesota is described and illustrated. Major ions, nitrogen and other nutrients, and pesticides and some of their breakdown compounds were analyzed in both surface and ground water. Biological communities that included fish, invertebrates, and algae, were described in relation to stream water quaAuthorsStephen J. Kalkhoff, Kimberlee K. Barnes, Kent Becher, Mark E. Savoca, Douglas J. Schnoebelen, Eric M. Sadorf, Stephen D. Porter, Daniel J. SullivanWater quality in the Allegheny and Monongahela River basins, Pennsylvania, West Virginia, New York, and Maryland, 1996-98
Major influences and findings for ground water quality, surface water quality, and biology in the Allegheny and Monongahela River basins are described and illustrated. Samples were collected in a variety of media to determine trace elements, sulfate, pesticides, nitrate, volatile organic compounds, organochlorine compounds, and radon-222. This report discusses the influences of several land-use prAuthorsRobert M. Anderson, Kevin M. Beer, Theodore F. Buckwalter, Mary E. Clark, Steven D. McAuley, James I. Sams, Donald R. WilliamsWater quality in the upper Mississippi River basin, Minnesota, Wisconsin, South Dakota, Iowa, and North Dakota, 1995-98
The report summarizes major findings about water quality in part of the upper Mississippi River basin that emerged from an assessment conducted from 1995 to 1998 by the NAWQA Program. Water quality is discussed in terms of local and regional issues and compared to conditions in the other 36 NAWQA study units assessed to date. Findings are also explained in the context of selected national benchmarAuthorsJames R. Stark, P. E. Hanson, R. M. Goldstein, J. D. Fallon, A. L. Fong, K. E. Lee, S. E. Kroening, W. J. AndrewsWater quality in the central Arizona basins, Arizona, 1995-98
The water quality in rivers and streams and in selected aquifers in central Arizona basins in Arizona is described and illustrated. Major ions, nitrogen and other nutrients, and pesticides and some of their breakdown compounds were analyzed in both surface and ground water. Biological communities that included fish, invertebrates, and algae, were described in relation to stream water quality. VolaAuthorsGail E. Cordy, Dorinda J. Gellenbeck, Joseph B. Gebler, David W. Anning, Alissa L. Coes, Robert J. Edmonds, Julie A.H. Rees, H. W. SangerWater quality in the upper Tennessee River basin, Tennessee, North Carolina, Virginia, and Georgia 1994-98
This report summarizes major findings about water quality in the upper Tennessee River basin that emerged from an assessment conducted between 1994 and 1998 by the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program. Water quality is discussed in terms of local and regional issues and compared to conditions found in all 36 NAWQA study areas, called study units, assessedAuthorsPaul S. Hampson, M.W. Treece, Gregory C. Johnson, Steven A. Ahlstedt, Joseph F. ConnellWater quality in the upper Colorado River basin, Colorado, 1996-98
This report summarizes major findings about water quality in the upper Colorado River basin that emerged from an assessment conducted between 1996 and 1998 by the U.S. Geological Survey (USGS) National Water Quality Assessment (NAWQA) Program. Water quality is discussed in terms of local and regional issues and compared to conditions found in all 36 NAWQA study areas assessed to date. Findings areAuthorsNorman E. Spahr, Lori E. Apodaca, Jeffrey R. Deacon, Jeffrey B. Bails, Nancy J. Bauch, C. Michelle Smith, Nancy E. DriverWater quality in south-central Texas, Texas, 1996–98
This report summarizes major findings about water quality in south-central Texas that emerged from an assessment conducted between 1996 and 1998 by the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program. Water quality is discussed in terms of local and regional issues and compared to conditions found in all 36 NAWQA study areas, called Study Units, assessed to date. FiAuthorsPeter W. Bush, Ann F. Ardis, Lynne Fahlquist, Patricia B. Ging, C. Evan Hornig, Jennifer Lanning-RushWater quality in the Santee River basin and coastal drainages, North and South Carolina, 1995-98
Surface water sampled in the Santee River basin and coastal drainages generally meets existing Federal and State guidelines for drinking-water quality and protection of aquatic life. However, urban and agricultural land uses have affected water quality, as indicated by elevated concentrations of bacteria, pesticides, and nutrients in basins dominated by these land uses.AuthorsW. Brian Hughes, Thomas A. Abrahamsen, Terry L. Maluk, Eric J. Reuber, Lance J. Wilhelm