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Regional water-level changes for the Cambrian-Ordovician aquifer in Iowa, 1975 to 1997

Water-Resources Investigations Report 99-4134

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

The Cambrian-Ordovician aquifer is one of the principal sources of ground water for industry and municipalities in Iowa. The 1998 Iowa Administrative Code Chapter 52.4(3) states that water levels in the Cambrian-Ordovician aquifer are not to decline more than 200 feet from the 1977 baseline. The potentiometric-surface map of the Cambrian-Ordovician aquifer, known locally as the Jordan aquifer, prepared by the Iowa Department of Natural Resources-Geological Survey Bureau and the U.S. Geological Survey in 1978 using water levels measured during the 1975 water year is considered the 1977 baseline.

For this study, water levels measured during the 1997 water year were used to construct a potentiometric-surface map that was compared to the 1977 baseline to describe water-level changes. Since 1975, water levels have declined in two areas of central and eastern Iowa. The maximum measured water-level decline is 133 feet in Johnson County in eastern Iowa. The estimated maximum rate of decline is 6 feet per year in Johnson County.

Results from a two-layer, ground-water flow model of the Cambrian-Ordovician aquifer constructed by the U.S. Geological Survey in 1990 were compared to selected measured 1997 water levels. The difference between the simulated water levels and the 1997 maximum measured water levels ranges from 0 to about 150 feet, but most differences are less than 25 feet. The comparison indicates that the model may help estimate future water levels in the Cambrian-Ordovician aquifer as an aid in managing the resource.

Study Area

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Regional water-level changes for the Cambrian-Ordovician aquifer in Iowa, 1975 to 1997
Series title:
Water-Resources Investigations Report
Series number:
99-4134
Year Published:
1999
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Iowa City, IA
Contributing office(s):
Iowa Water Science Center
Description:
iv, 11 p.
Country:
United States
State:
Iowa
Other Geospatial:
Cambrian-Ordovician Aquifer
Online Only (Y/N):
N
Additional Online Files (Y/N):
N