Full Description

Regional aquifer systems provide vast supplies of water to many important industrial andirrigation centers. The large storage capacity of these aquifers often leads to overpumping, which causes declining water levels and deteriorating water quality. TheCambrian-Ordovician sandstone aquifer system (the sandstone aquifer) of southeasternWisconsin is a good illustration of the effect of over pumping. The aquifer is separatedfrom two shallower aquifers, the glacial drift aquifer and the Silurian dolomite aquifer, bya regional confining unit that consists of the Maquoketa formation and the underlyingGalena-Platteville dolomite. This confining unit severely limits the vertical migration ofwater between the upper aquifers and the sandstone aquifer. In 1995 the sandstoneaquifer supplied approximately 95% of municipal pumpage in Waukesha County, whichabuts Milwaukee County along its eastern border. The aquifer is also the only source ofmunicipal water for many communities in eastern Wisconsin.Pumpage from the sandstone aquifer has created a large cone of depression centered ineastern Waukesha County (SEWRPC 2002). Now, the historically good water quality isexperiencing rising levels of total dissolved solids (TDS). In response to these conditions,a sophisticated groundwater model of the flow system of southeastern Wisconsin has justbeen completed. The Southeast Wisconsin Regional Groundwater Model was constructedby the Southeast Wisconsin Regional Planning Commission with assistance from theUnited States Geological Survey (USGS) and the Wisconsin Geological and NaturalHistory Survey (WGNHS) (SEWRPC in press). The SEWRPC model is a three-dimensionalMODFLOW model of the shallow and deep groundwater flow system ofsoutheastern Wisconsin. This tool is making possible detailed analysis of theconsequences of prolonged draw down on the sandstone aquifer.Pumpage from the sandstone aquifer has changed the groundwater flow of the aquifer.Over time there has been increased drawdown and gradient to the west of the Maquoketasubcrop and a reversal of the groundwater flow to the east along the Lake Michiganshoreline. In addition, the head in the aquifer continues to decline while the cone ofdepression increases in size. There has also been a decline in water quality as water isbeing mined from more stagnant portions of the aquifer. Contrary to the position thatpumping from a deeper confined aquifer will avoid detrimental impacts to the shallowsystem, the data suggests that it only delays the impact to the shallow system and theeventual result will affect a larger area. Includes 6 references, figures.

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Edition: Vol. - No. Published: 06/17/2004 Number of Pages: 18File Size: 1 file , 1 MB