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)
NWQP Water-Quality Topics
Groundwater Quality Research
Groundwater Quality in Principal Aquifers of the Nation, 1991–2010
Surface-Water Quality and Ecology
Water-Quality Trends From Lake Cores
National Water-Quality Project Sampling Methods
- 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.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.
Sources/Usage: Public Domain.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)
- 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.NWQP Water-Quality Topics
From chloride to corrosivity, from pesticides to PAHs, find the most recent National Water Quality Program (NWQP) science on these topics and effects on surface water, groundwater, and ecology. Informative web pages provide an overview and links to related web pages, publications, maps, news, and data.Groundwater Quality Research
Every day, millions of gallons of groundwater are pumped to supply drinking water for about 140 million people, almost one-half of the Nation’s population. Learn about the quality and availability of groundwater for drinking, where and why groundwater quality is degraded, and where groundwater quality is changing.Groundwater Quality in Principal Aquifers of the Nation, 1991–2010
What’s in your groundwater? Learn about groundwater quality in the Principal Aquifers of nine regions across the United States in informative circulars filled with figures, photos, and water-quality information.Surface-Water Quality and Ecology
Research by the USGS National Water Quality Assessment (NAWQA) Project on water quality of rivers and streams covers a broad range of topics, from nonpoint pollution issues to vulnerability of aquatic ecosystems. Dive in and find out more about current water-quality conditions, how and where water quality is changing, and the latest information on pesticides, nutrients, and other contaminants.Water-Quality Trends From Lake Cores
Sediment cores let us look back in time at the contaminant history of a watershed. Learn about what lake and reservoir sediment cores tell us about trends in metals, organochlorine pesticides, polycyclic aromatic hydrocarbons, and other sediment-related contaminants.National Water-Quality Project Sampling Methods
USGS National Water Quality Assessment (NAWQA) studies require analyses of stream and bed-sediment samples for major ions, nutrients, sediments, and organic contaminants that are consistent across time and space. Procedures have been designed specifically to produce information that is comparable among studies in different parts of the Nation. - Publications