Hydrologic data for a study of pre-Illinoian glacial till in Linn County, Iowa, water year 1990

Open-File Report 91-459

Prepared in cooperation with the Iowa Department of Natural Resources, Geological Survey Bureau



Hydrologic data for a study of pre-lllinoian glacial till were collected during the 1990 water year at a site in Linn County, Iowa. A hydrologic-data-collection network, consisting of 22 observation wells and a meteorological station, was installed at the site to describe the hydraulic properties of the till. Recorders were installed on 12 of the wells to continuously monitor water levels.

Rainfall at the study site from April to October 1990, totaled 35.49 inches. The greatest monthly rainfall (13.15 inches) occurred in June. The greatest daily rainfall (6.00 inches) occurred on June 16.

For the 16 wells less than 50 feet in depth, the highest water levels were recorded during the 4 months of greatest rainfall (May-August 1990). Water levels in the four deepest wens, completed in unconsolidated material, rose throughout the data-collection period. One well had water levels greater than the top of the well casing for most of the period from mid-May to mid-September 1990.

A water-quality minimonitor was installed on one observation well near the top of the water table to monitor temporal changes in groundwater quality. For April through September 1990, the daily mean specific conductance ranged from 705 to 864 microsiemens per centimeter at 25 degrees Celsius, the daily mean water temperature ranged from 5.2 to 15.6 degrees Celsius, and the daily median pH remained nearly constant at 7.0 to 7.2 standard units.

Ten unvented, vibrating-wire, pressure transducers with internal thermistors were buried in two boreholes at upgradient and downgradient locations to record hydraulic pressure arid water temperature at selected depths.

Study Area

Additional publication details

Publication type:
Publication Subtype:
USGS Numbered Series
Hydrologic data for a study of pre-Illinoian glacial till in Linn County, Iowa, water year 1990
Series title:
Open-File Report
Series number:
Year Published:
U.S. Geological Survey
Publisher location:
Iowa City, IA
Contributing office(s):
Iowa Water Science Center
iv, 70 p.: map; 28 cm.
United States
Linn County
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