National Water-Quality Assessment Program
Nutrients in the Nation's Waters--Too Much of a Good Thing?
U.S. Geological Survey Circular 1136
Nutrients are essential for plant and animal growth and nourishment,
but the overabundance of certain nutrients in water can cause a number
of adverse health and ecological effects. To determine the extent of
nutrient and other types of contamination in the Nation's streams and
ground water, Congress has appropriated funds for a National
Water-Quality Assessment (NAWQA) Program, conducted by the
U.S. Geological Survey (USGS). The objectives of the NAWQA Program
are to:
- Describe current water-quality conditions for a large part of
the Nation's freshwater streams, rivers, and ground-water aquifers.
- Describe how water quality is changing over time.
- Improve understanding of the primary natural and human factors
that affect water-quality conditions.
These goals are being achieved through investigations in 60 large
river basins and aquifer systems, which are referred to as study
units. Implementation of study-unit investigations are phased so that
data are collected in 20 areas at a time. Investigations in the
initial 20 study units began in 1991, and reports are being written in
1996. Another group of study-unit investigations began in 1994, and a
third group are scheduled to begin in 1997.
(26K GIF)
This report is based on data compiled from electronic data bases of
the USGS and other Federal, State, and local agencies at locations
within the first 20 NAWQA study units.
(96K GIF)
About 12,000 samples collected
from wells in the NAWQA study units and five additional USGS study
areas were used in the ground-water analysis.
(83K GIF)
Data from streams consisted of more than 22,000 samples collected at
more than 300 sites between October 1979 and September 1990.
