National Water Quality Assessment Program: Eastern Iowa Basins

Water-quality Differences Between Urban And Agricultural Areas Of Alluvial Aquifers In Eastern Iowa And Part Of Southern Minnesota, 1997

by S.J. Kalkhoff and M.E. Savoca

Program abstract of the 110th Session of the Iowa Academy of Science meeting, April 25, 1998, Mason City, Iowa


A study was conducted in the Wapsipinicon, Cedar, Iowa, and Skunk River basins during June through July, 1997 to determine the effect of urban and agricultural land use on water quality in shallow alluvial aquifers--the major ground-water supply source in the basins. The study was part of the U.S. Geological Survey's National Water Quality Assessment. Monitoring wells were installed in urban (31 wells) and agricultural (30 wells) areas. The average screened interval was 6.5 to 11.5 feet below the water table.

Ground water from alluvial aquifers in samples from urban areas, on average, contained greater dissolved-solids concentrations, more pesticide compounds, and over eight times the number of volatile organic compounds (VOC) than ground water in alluvial aquifers in samples from agricultural areas. Ground water in alluvial aquifers from agricultural areas contained significantly greater nitrate and pesticide concentrations than in ground water in alluvial aquifers from urban areas. Average dissolved-solids concentration was 471 mg/l (milligrams per liter); average nitrate concentration was 2.9 mg/l; and the average total pesticide concentration was 0.17 ug/l (micrograms per liter) in samples from urban areas. The average dissolved-solids concentration was 308 mg/l; average nitrate was 9.3 mg/l; and the average total pesticide concentration was 1.3 ug/l in in samples from agricultural areas. The nitrate concentration exceeded 10 mg/l in 39 percent of the samples from agricultural areas and in none of the samples from urban areas. Deethylatrazine was the most commonly detected (80.6%) pesticide in samples from agricultural areas and atrazine was the most commonly detected (50%) pesticide in samples from urban areas.


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