SUMMARY OF MAJOR FINDINGS
|Land use in the Lake Erie-Lake Saint
Claire Drainage was predominatly agricultural and urban. This level
of human activity has substantial effects on water quality in the
Stream and River Highlights
Water quality in the Lake Erie-Lake Saint Clair Drainages
is greatly influenced by land use and human activities. A major pathway
for contaminant transfer from the land surface to streams is storm runoff
from urban and agricultural areas.
As a result of herbicides in runoff, concentrations
in streams were in the top 25 percent of streams nationwide and many public-water
supplies must treat stream water to reduce herbicide concentrations. As
a result of nutrients in runoff, concentrations of total phosphorus and
nitrate in some small streams in agricultural areas and in major rivers
were in the top 25 percent of streams nationwide. Concentrations of nitrate,
although elevated relative to many other streams in the Nation, were infrequently
greater than the drinking-water standard of 10 milligrams per liter.
- Contamination of the bed sediments of small streams
and major rivers by persistent and bioaccumulative contaminants was
prevalent. The highest concentrations of PCBs (polychlorinated biphenyls)
and mercury were detected in streams draining highly populated urban
and mixed land-use areas. Detections of contaminants in fish tissues
indicate bioaccumulation; in fact, bioaccumulation of PCBs and DDT in
some fish species presents a health risk to fish-eating wildlife.
- The pesticides detected most frequently were among
those applied in the greatest quantities to agricultural and mixed land-use
areas. The herbicides atrazine, acetochlor, cyanazine, metolachlor,
and simazine were detected in 50 to 100 percent of samples. (p.
- Several heavily used herbicides and insecticides
were detected in spring and summer at or above a standard for drinking
water or a guideline for aquatic life. Elevated pesticide concentrations
in streams persisted for 4 to 6 weeks after applications in agricultural
and mixed-land-use areas. (p.
- Annual average concentrations of total phosphorus
were greater than the U.S. Environmental Protection Agency recommended
level for control of nutrient enrichment at 8 of 10 sites sampled in
small streams and major rivers draining agricultural and mixed-use land.
Streams draining row-crops and mixed-use land are major pathways of
phosphorus to Lake Erie. (p. 10)
- Contaminants detected most often in the bed sediments
of small streams and major rivers were arsenic, cadmium, copper, lead,
mercury, zinc, PCBs, and PAHs (polycyclic aromatic hydrocarbons). The
concentrations of arsenic, mercury, PCBs, and PAHs were equal to or
greater than sediment guidelines, indicating probable adverse effects
on aquatic life, in about 11 to 30 percent of samples. (p.
- The most frequently detected contaminants in fish
were highly persistent contaminants—DDT, chlordane, dieldrin, PCBs,
and mercury. Except for mercury, use of these compounds in industry
and agriculture in the United States was discontinued 15 to 25 years
ago. (p. 14)
- Agricultural land use appears to be affecting fish
communities in streams draining areas of row-crops. As the amount of
row-crops increased relative to forested land, the number of pollution-intolerant
fish species decreased. It appears that pollution-intolerant fish can
live where agriculture is the primary land use when streams are protected
by natural cover. (p. 17)
Major Influences on Surface-Water
Quality and Aquatic Biota
- Storm runoff
- Land use and chemical releases
- Bioaccumulative and persistent contaminant
Trends in Surface-Water Quality
Suspended-sediment discharges from the Maumee River
Basin decreased by 11.2 percent over the period 1970–98 and corresponded
to increased use of conservation tillage to control soil erosion.
Ground Water Highlights
The glacial aquifer is the major source of drinking
water in the northwestern part of the study area. In this area, ground-water
quality is affected by a combination of human and natural factors. Land
use determines which chemicals are used; how readily these chemicals are
transported to the ground water is affected by geology.
In residential areas underlain by sand and gravel, more than 75 percent
of ground water recharged since 1953 shows evidence of human activities
in the form of nitrate, chloride, or volatile organic compounds (VOCs).
Probable sources are (1) septic systems containing human waste and household
chemicals, (2) road salt and gasoline residue from paved surfaces, (3)
waste from water softeners, or (4) lawn fertilizer. Pesticides were
rarely detected. (p. 18)
- In the agricultural study area, which is underlain
by till, nitrate and herbicides were detected less frequently than in
most other agricultural areas of the Nation. This observation partially
supports the belief that till or tile drains protect the aquifer from
contamination. Nevertheless, the ground water is still vulnerable to
contamination; almost 60 percent of shallow ground water contained herbicides
or elevated concentrations of nitrate. Herbicides were predominantly
detected as breakdown products. (p.
- In residential and agricultural areas, samples from
domestic wells met health-related drinking-water standards. However,
ground water affected by human activities was detected at depths below
25 feet, the minimum required depth for wells in Ohio and Michigan.
Major Influences on Ground-Water
- Septic systems, roads, and lawns in residential
- Herbicides and fertilizer in agricultural
- Geology, especially deposits at land surface
- Well depth and ground-water age
Trends in Ground-Water Quality
A significant change in ground-water quality is linked
to recent residential development near Detroit. Ground water recharged
before 1953 (which predates suburbanization) has concentrations of chemical
constituents typical of natural water. In contrast, ground water recharged
after 1953 has significantly higher concentrations of constituents derived
from human activities.
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U.S. Geological Survey Circular
Myers, D.N., Thomas, M.A., Frey, J.W., Rheaume, S.J., and Button, D.T., 2000, Water Quality in the Lake Erie-Lake Saint Clair Drainages Michigan, Ohio, Indiana, New York, and Pennsylvania, 199698: U.S. Geological Survey Circular 1203, 35 p., on-line at http://pubs.water.usgs.gov/circ1203/