ISSN:
1745-6584
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Energy, Environment Protection, Nuclear Power Engineering
,
Geosciences
Notes:
The Cambrian-Ordovician aquifer (deep sandstone aquifer) of northeastern Illinois and southeastern Wisconsin consists of a number of hydraulically connected sandstone and dolomite units. The aquifer dips gently to the east beneath Lake Michigan and is regionally confined by the Maquoketa shale, which has been thinned and removed by erosion to the west. Recharge to the regional aquifer system occurs where the shale is missing and to a lesser extent across the shale wherever there are downward hydraulic gradients. The practical sustained yield from the aquifer is 46 million gallons per day (mgd) (170,000 m3/day) in Illinois and approximately 34 mgd (129,000 m3/day) in Wisconsin. In 1978, pumpage from the aquifer amounted to 142 mgd (537,000 m3/day) in the eight counties of northeastern Illinois compared with an estimated 38 mgd (144,000 m3/day) in Wisconsin. Pumpage in Illinois has exceeded the practical sustained yield every year since 1958 while in Wisconsin the practical sustained yield was reached about 1975. Two regional pumping cones have developed. One centered in the Chicago region has maximum drawdowns of more than 900 feet (275 m) while in the Milwaukee pumping cone water levels have fallen about 350 feet (106 m). The greater drawdown in the Chicago pumping cone has changed the regional hydraulic gradient and 9.3 mgd (35,200 m3/day) of ground water is now being drained from beneath Wisconsin into Illinois. A digital computer model of the aquifer system was used to separate the amount of total drawdown in the aquifer attributable to each pumping center as well as to predict future ground-water levels. At the Illinois-Wisconsin border in 1973, there was 265 feet (81 m) of drawdown of which 94 feet (28 m) were due to pumpage in Wisconsin and 171 feet (52 m) due to pumpage in Illinois. Allocations of Lake Michigan water to ground-water users in Illinois could result in a reduction of pumpage to less than 46 mgd (174,000 m3/day) by 1985. In order to obtain a modification of the U.S. Supreme Court decree permitting Illinois to divert 3,200 cubic feet per second (cfs) (7,829,000 m3/day) of water from Lake Michigan, Illinois must agree that future allocations of Lake Michigan water will be done in such a manner as to reduce Cambrian-Ordovocian aquifer pumpage. The rate of ground-water decline will decrease substantially if this occurs. Water resources managers in southeastern Wisconsin should limit pumpage from the deep sandstone aquifer to approximately the current rate.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1745-6584.1981.tb03459.x
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