Red River of the North Basin
National Water-Quality Assessment Program
Tornes, L.H. and Brigham, M.E., 1994, Nutrients, Suspended Sediment, and
Pesticides in Waters of the Red River of the North Basin, Minnesota, North
Dakota, and South Dakota, 1970-1990. U.S. Geological Survey,
Water-Resources Investigations Report 93-4231.
Abstract
Available data on nutrients (phosphorus and nitrogen), suspended sediment, and
pesticides in the Red Rive of the North Basin, a study unit under the U.S.
Geological Survey National Water-Quality Assessment (NAWQA) Program, are
reviewed. These data were collected by several agencies during 1970-90.
Nutrient concentrations in surface water are higher downgradient from agricultural and urban areas than in other areas, but
generally do not exceed U.S. Environmental Protection Agency (USEPA) Maximum
Contaminant Levels (MCLs). The 10 milligram per liter (mg/L) drinking water
MCL for nitrate (as nitrogen) was rarely exceeded. Some of the largest
nutrient inputs to the surface-water system appear to come from the
Fargo-Moorhead area. The highest nitrogen concentrations usually were found
in the Red River of the North. Nitrogen composition was mostly organic
nitrogen with some nitrate. Ammonia nitrogen was negligible except during
mid-winter, when concentrations could exceed 1.0 mg/L. Streams draining the
corn-dominated cropland in the southern part of the basin had relatively high
nitrogen concentrations compared to parts of the basin where small-grain
crops, forests, and wetlands predominate. The Pembina River in the northern part of the basin had a large range in nitrogen concentrations that often exceeded those in the Red River of the North. The highest phosphorus concentrations generally were found in of the Red River of the North, although tributary streams occasionally had peak concentrations that exceeded those in the Red River of the North. Median nitrate concentrations in ground water were less than 1.0 mg/L as nitrogen in all counties in the basin except in Otter Tail and Becker Counties in Minnesota. Half of the wells in Otter Tail County had nitrate-nitrogen concentrations exceeding 2.8 mg/L. Shallow, surficial aquifers tended to have the highest nitrate concentrations.
Median suspended-sediment concentrations were less than 100 mg/L except in the Red River of the North near the Canadian border at Emerson, Manitoba and the Pembina River. The Pembina River occasionally had high suspended sediment concentrations; about 10 percent of the samples exceeded 2,000 mg/L.
For both surface and ground water, available pesticide data were limited in spatial and temporal coverage. The majority of pesticide analyses for the Red River of the North Basin show no concentrations above laboratory reporting limits. Reported concentrations usually were below USEPA MCLs. Only a few analyses of pesticides in ground water had concentrations above laboratory reporting limits. Wells that had reportable levels are mainly in the southern and southeastern part of the basin, where atrazine was the most commonly detected pesticide.
A relatively large fraction of stream samples had detectable quantities of
2,4-D, a- and g-HCH, and atrazine. These samples covered time spans of as
much as 15 years and were from sites downstream from large drainage basins;
however, concentrations were well below USEPA MCLs. One county-level study
showed higher 2,4-D concentrations at upstream sites than at the outlet from a
small basin. This indicates that downstream sites may fail to show impaired
water-quality and the fate of pesticides used in the basin. Following the
1972 ban on DDT, concentrations of DDT in fish samples from the Red River of
the North quickly decreased. Fish concentrations of DDE and DDD decreased
more slowly. Low levels of DDE and DDD were detected in fish 14 years after
the DDT ban.
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U.S. Geological Survey
