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    Ground-Water Contamination and Land Management in the Karst Area of Northeastern Iowa

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    A statistical analysis of existing northeast Iowa water-quality data showed that systematic nonpoint contamination of ground-water quality was occurring in regional carbonate aquifers. Well-water quality generally improved with increased well depth and with natural geologic protection related to thickness of overlying bedrock or Quaternary aquitards. Nitrate levels were highest in areas where sinkholes were present; areas without sinkholes but with relatively thin protective cover had similar but somewhat lower levels of nitrate.

    A detailed analysis of a single karst ground-water basin found the same systematic nitrate contamination along with low but persistent levels of herbicides. Agricultural practices were judged to be the sourceof the contaminants and infiltration was the principal mechanism. Ninety-five percent of the nitrate and 55 to 85% of the atrazine were delivered by infiltration and percolation.

    Various state and Federal agencies, university researchers, local groups, and private organizations are cooperating in a seven-year project in the Big Spring basin to demonstrate and evaluate the effectiveness of best management practices on ground-water quality and on crop production. The project will provide research results to serve as a foundation for future policies and programs that agriculture must address relative to environmental problems.


    ground water, carbonate aquifers, karst, contamination, pesticides (herbicides), nitrates, bacteria (coliform), infiltration/percolation, fertilization, agriculture, soil conservation

    Author Information:

    Stan Mitchem, P
    State geologist, USDA Soil Conservation Service, Casper, WY

    Hallberg, GR
    Geologists, Iowa Geological Survey, Iowa City, IA

    Hoyer, BE
    Geologists, Iowa Geological Survey, Iowa City, IA

    Libra, RD
    Geologists, Iowa Geological Survey, Iowa City, IA

    Committee/Subcommittee: D18.21

    DOI: 10.1520/STP44879S