WATER QUALITY ASSESSMENT OF THE EASTERN
IOWA BASINS: BASIC WATER CHEMISTRY OF RIVERS AND STREAMS, 1996-98
Kymm Barnes, Hydrologist, U.S. Geological Survey, Water Resources
Division
Proceedings from Agriculture and the Environment: State and Federal
Initiatives conference at Iowa State University, March 5-7, 2001
The U.S. Geological Survey began data-collection activities in
the Eastern Iowa Basins study unit of the National Water-Quality
Assessment Program in September 1995 with the purpose of determining
the status and trends in water quality of water from the Wapsipinicon,
Cedar, Iowa, and Skunk River basins. From March 1996 through September
1998, monthly surface-water samples were collected from 11 sites
on the study's rivers and streams representing three distinct
physiographic regions, the Des Moines Lobe, the Iowan Surface,
the Southern Iowa Drift Plain, and one subregion, the Iowan Karst.
These water samples were analyzed for basic water chemistry, including,
but not limited to the following cations: sodium, potassium, magnesium,
calcium, and silica; anions: chloride, fluoride, sulfate, and
bicarbonate; and two metals - iron and maganese. Although none
of the concentrations of the constituents exceeded health advisories
or drinking-water regulations, extremely high or low concentrations
could potentially affect aquatic life. Calcium, magnesium, and
potassium are essential elements for both plant and animal life;
manganese is an essential element in plant metabolism; and silica
is important in the growth of diatom algae. Calcium had the largest
median concentration of 61 milligrams per liter (mg/L) of the
cations, and the largest maximum concentration of 100 mg/L. Bicarbonate
had the largest median concentration of 210 mg/L of the anions,
and the largest maximum concentration of 400 mg/L.
Basic water-quality differences related to physiographic differences
and seasonality were evident in streams and rivers in the Eastern
Iowa Basins. Of the three major landforms, water samples from
sites within the Des Moines Lobe, the youngest landform in the
study area, had significantly higher median concentrations of
calcium (85 mg/L), magnesium (28 mg/L), sulfate (28 mg/L), fluoride
(0.31 mg/L), and silica (16 mg/L). The Des Moines Lobe region
is calcium magnesium bicarbonate-rich due to the Paleozoic source
rocks (limestones and shales) in the bedrock. Water samples from
sites within the Southern Iowa Drift Plain had higher median concentrations
of sodium (12 mg/L), potassium (3.2 mg/L), and chloride (21 mg/L).
Concentrations also varied according to the time of year. Grouping
the data into four seasonal periods, water samples collected during
the months of October, November, and December, had higher median
concentrations of calcium, magnesium, and chloride, then samples
collected during other quarters of the year. Water quality in
the streams during this low-flow period (October through December)
is representative of that in the contributing aquifers.
U.S. Department of the Interior
| U.S. Geological Survey
URL: http://ia.water.usgs.gov/nawqa/abstracts/ISU2001.basicchem.html
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