National Water-Quality Assessment (NAWQA) Program
U.S. Geological Survey
Nutrients in the Nation's Waters--Too Much of a Good Thing?
By David K. Mueller and Dennis R. Helsel
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, we analyzed data from about 12,000 ground-water samples
and more than 22,000 surface-water samples collected at more than 300
sites between October 1979 and September 1990. Most samples had been
collected within NAWQA study units. Nutrient concentrations in water
generally are related to land use in the upstream watershed or the
area overlying a ground-water aquifer. Nitrate concentrations were
generally higher in ground water than in streams. Concentrations were
highest in the Northeast, Great Plains, and along the West
Coast. Drinking water from public-supply wells and domestic-supply
wells outside of agricultural areas is not likely to have high levels
of nitrate. Domestic-supply wells in agricultural areas are more
prone to increased concentrations. Ammonia and phosphorus
concentrations in surface water are highest downstream from urban
areas. Where these concentrations are high, they warrant concerns
about decreased oxygen in the water, toxicity to fish, and accelerated
Table of Contents
- Major findings
- What parts of the Nation are most affected?
- What are nutrients?
- Are drinking-water supplies affected?
- What information can science provide for policy decisions?
- What are the concerns about nutrients in water?
- What are the sources of nutrients in water?
- How large are natural concentrations of nutrients in water?
- What are the major influences on nutrients concentrations in water?
Depth to ground water
- Is the nutrient situation getting better or worse?
- Where can I get more information?
- Other publications referred to in the report
- A coordinated effort
- Publications of the National Water-Quality Assessment (NAWQA)
Program related to data used in this report
For further information about this report, contact the National
Water-Quality Assessment Program office.