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 Delmarva Peninsula, Delaware, Maryland, and Virginia, 1999-2001
Water quality in the Great and Little Miami River Basins, Ohio and Indiana, 1999-2001
Water Quality in the Great Salt Lake Basins, Utah, Idaho, and Wyoming, 1998-2001
Water Quality on the Island of Oahu, Hawaii, 1999-2001
Water quality in the lower Tennessee River Basin, Tennessee, Alabama, Kentucky, Mississippi, and Georgia, 1999-2001
Water quality in the Mobile River Basin, Alabama, Georgia, Mississippi, and Tennessee, 1999-2001
Water Quality in the Santa Ana Basin, California, 1999-2001
Water quality in the upper Illinois River basin: Illinois, Indiana, and Wisconsin, 1999-2001
Water Quality in the Yakima River Basin, Washington, 1999-2000
Water quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999-2001
Water quality in the Acadian-Pontchartrain drainages: Louisiana and Mississippi, 1999–2001
Water quality in the New England coastal basins, Maine, New Hampshire, Massachusetts, and Rhode Island, 1999-2001
- 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 Delmarva Peninsula, Delaware, Maryland, and Virginia, 1999-2001
This report contains the major findings of a 1999-2001 assessment of water quality in the Delmarva Peninsula. 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 assessed at many scales?from local ground-water flow paths to regAuthorsJudith M. Denver, Scott W. Ator, Linda M. Debrewer, Matthew J. Ferrari, Jeffrey R. Barbaro, Tracy C. Hancock, Michael J. Brayton, Mark R. NardiWater quality in the Great and Little Miami River Basins, Ohio and Indiana, 1999-2001
This report contains the major findings of a 1999?2001 assessment of water quality in the Great and Little Miami River 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 regionalAuthorsGary L. Rowe, David C. Reutter, Donna L. Runkle, Julie A. Hambrook, Stephanie D. Janosy, Lee H. HwangWater Quality in the Great Salt Lake Basins, Utah, Idaho, and Wyoming, 1998-2001
This report contains the major findings of a 1998-2001 assessment of water quality in the Great Salt Lake 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 issues. CondAuthorsKidd M. Waddell, Steven J. Gerner, Susan A. Thiros, Elise M. Giddings, Robert L. Baskin, Jay R. Cederberg, Christine M. AlbanoWater Quality on the Island of Oahu, Hawaii, 1999-2001
This report contains the major findings of a 1999-2001 assessment of water quality on the island of Oahu, Hawaii. 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. ConditionAuthorsStephen S. Anthony, Charles D. Hunt, Anne M.D. Brasher, Lisa D. Miller, Michael S. TomlinsonWater quality in the lower Tennessee River Basin, Tennessee, Alabama, Kentucky, Mississippi, and Georgia, 1999-2001
This report contains the major findings of a 1999?2001 assessment of water quality in the Lower Tennessee 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.AuthorsMichael D. Woodside, Anne B. Hoos, James A. Kingsbury, Jeffrey R. Powell, Rodney R. Knight, Jerry W. Garrett, Reavis L. Mitchell, John A. RobinsonWater quality in the Mobile River Basin, Alabama, Georgia, Mississippi, and Tennessee, 1999-2001
This report contains the major findings of a 1999?2001 assessment of water quality in the Mobile 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. ConditioAuthorsJ. Brian Atkins, Humbert Zappia, James L. Robinson, Ann K. McPherson, Richard S. Moreland, Douglas A. Harned, Brett F. Johnston, John S. HarvillWater Quality in the Santa Ana Basin, California, 1999-2001
This report contains the major findings of a 1999-2001 assessment of water quality in the Santa Ana 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. CondiAuthorsKenneth Belitz, Scott N. Hamlin, Carmen A. Burton, Robert Kent, Ronald G. Fay, Tyler D. JohnsonWater quality in the upper Illinois River basin: Illinois, Indiana, and Wisconsin, 1999-2001
This report contains the major findings of a 1999?2001 assessment of water quality in the upper Illinois 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.AuthorsGeorge E. Groschen, Terri Arnold, Mitchell A. Harris, David H. Dupre, Faith A. Fitzpatrick, Barbara C. Scudder, William S. Morrow, Paul J. Terrio, Kelly L. Warner, Elizabeth A. MurphyWater Quality in the Yakima River Basin, Washington, 1999-2000
This report contains the major findings of a 1999?2000 assessment of water quality in streams and drains in the Yakima River Basin. It is one of a series of reports by the NAWQA Program that present major findings on water resources in 51 major river basins and aquifer systems across the Nation. In these reports, water quality is assessed at many scales?from large rivers that drain lands hAuthorsGregory J. Fuhrer, Jennifer L. Morace, Henry M. Johnson, Joseph F. Rinella, James C. Ebbert, Sandra S. Embrey, Ian R. Waite, Kurt D. Carpenter, Daniel R. Wise, Curt A. HughesWater quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999-2001
This report contains the major findings of a 1999?2001 assessment of water quality in the Yellowstone 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. ConditiAuthorsDavid A. Peterson, Timothy T. Bartos, Melanie L. Clark, Kirk A. Miller, Stephen D. Porter, Thomas L. QuinnWater quality in the Acadian-Pontchartrain drainages: Louisiana and Mississippi, 1999–2001
This report contains the major findings of a 1999-2001 assessment of water quality in the Acadian-Pontchartrain Drainages Study Unit. 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 regionalAuthorsDennis K. Demcheck, Roland W. Tollett, Scott V. Mize, Stanley C. Skrobialowski, Robert B. Fendick, Christopher M. Swarzenski, Stephen PorterWater quality in the New England coastal basins, Maine, New Hampshire, Massachusetts, and Rhode Island, 1999-2001
This report contains the major findings of a 1999-2001 assessment of water quality in the New England Coastal 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 issues. ConditioAuthorsKeith W. Robinson, Sarah M. Flanagan, Joseph D. Ayotte, Kimberly W. Campo, Ann Chalmers, James F. Coles, Thomas F. Cuffney