Regional aquifer systems provide vast supplies of water to many important industrial and
irrigation centers. The large storage capacity of these aquifers often leads to over
pumping, which causes declining water levels and deteriorating water quality. The
Cambrian-Ordovician sandstone aquifer system (the sandstone aquifer) of southeastern
Wisconsin is a good illustration of the effect of over pumping. The aquifer is separated
from two shallower aquifers, the glacial drift aquifer and the Silurian dolomite aquifer, by
a regional confining unit that consists of the Maquoketa formation and the underlying
Galena-Platteville dolomite. This confining unit severely limits the vertical migration of
water between the upper aquifers and the sandstone aquifer. In 1995 the sandstone
aquifer supplied approximately 95% of municipal pumpage in Waukesha County, which
abuts Milwaukee County along its eastern border. The aquifer is also the only source of
municipal water for many communities in eastern Wisconsin.
Pumpage from the sandstone aquifer has created a large cone of depression centered in
eastern Waukesha County (SEWRPC 2002). Now, the historically good water quality is
experiencing rising levels of total dissolved solids (TDS). In response to these conditions,
a sophisticated groundwater model of the flow system of southeastern Wisconsin has just
been completed. The Southeast Wisconsin Regional Groundwater Model was constructed
by the Southeast Wisconsin Regional Planning Commission with assistance from the
United States Geological Survey (USGS) and the Wisconsin Geological and Natural
History Survey (WGNHS) (SEWRPC in press). The SEWRPC model is a three-dimensional
MODFLOW model of the shallow and deep groundwater flow system of
southeastern Wisconsin. This tool is making possible detailed analysis of the
consequences 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 Maquoketa
subcrop and a reversal of the groundwater flow to the east along the Lake Michigan
shoreline. In addition, the head in the aquifer continues to decline while the cone of
depression increases in size. There has also been a decline in water quality as water is
being mined from more stagnant portions of the aquifer. Contrary to the position that
pumping from a deeper confined aquifer will avoid detrimental impacts to the shallow
system, the data suggests that it only delays the impact to the shallow system and the
eventual result will affect a larger area.
Includes 6 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 18 |
| Published : | 06/17/2004 |
