National Water-Quality Assessment (NAWQA) Project
NAWQA assessments of nutrients—including total nitrogen, nitrate, ammonia, total phosphorus, and orthophosphate—followed a nationally consistent approach in 51 of the Nation's major river basins and aquifer systems during 1992–2001 (shown in green). Water samples were collected from 499 stream sites monthly and during periods of both high and low stream flow, usually for a minimum of two years. Biological communities were assessed at about 1400 stream sites. Ground-water samples were collected from over 5,100 wells, including monitoring, domestic, and public-supply wells from 180 study areas (represented by yellow dots), with 30 wells sampled in each area.
A comprehensive national analysis of nutrients in streams and groundwater from 1992 through 2004 is provided by the National Water-Quality Assessment (NAWQA) Program of the United States Geological Survey (USGS).
Findings describe nutrient occurrence, key sources of nutrients, potential effects on humans and aquatic life, and changes in concentrations since the early 1990s. Results show that excessive nutrient enrichment is a widespread cause of ecological degradation in streams and that nitrate contamination of groundwater used for drinking water, particularly in shallow domestic wells in agricultural areas, is a continuing human-health concern. Despite major Federal, State, and local efforts to control point and non-point sources and transport of nutrients, concentrations of nutrients have remained the same or increased in many streams and aquifers across the Nation since the early 1990s.
Findings touch on many environmental issues, including those related to (1) developing nutrient criteria for surface water bodies, (2) reducing nutrient loadings to receiving waters, (3) setting realistic expectations for water-quality improvements following nutrient reduction strategies, and (4) managing elevated nutrients in drinking water from surface-water intakes and wells.
The results of this study are described in two USGS publications: a USGS Fact Sheet (2010-3078) highlights selected national findings and their implications, and serves as a companion product to the complete analysis reported in the USGS Circular (1350) titled “The Quality of Our Nation’s Waters—Nutrients in the Nation’s Streams and Groundwater, 1992–2004”. Both publications can be downloaded in PDF format (see below).
Neil Dubrovsky, USGS, Chief, NAWQA Nutrients National Synthesis
Placer Hall -- 6000 J Street
Sacramento, CA 95819-6129
Phone: (916) 278-3078