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

January 1, 1991

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.

Publication Year 1991
Title Hydrologic data for a study of pre-Illinoian glacial till in Linn County, Iowa, water year 1990
DOI 10.3133/ofr91459
Authors Phillip R. Bowman
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 91-459
Index ID ofr91459
Record Source USGS Publications Warehouse
USGS Organization Iowa Water Science Center