Well Good

Sort hydrogeological myths from facts before setting water precedents

By DOUG CHERKAUER, NANCY FRANK, TIM GRUNDL and VAL KLUMP

Posted: Oct. 7, 2006

As faculty members of the University of Wisconsin-Milwaukee and members of the Great Lakes WATER Institute, we realize the sustainable management of water is central to a thriving political, economic and environmental future in southeastern Wisconsin.

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We are concerned that misperceptions could undermine science-based management. We hope to serve the public and enhance regional dialogue with unbiased fact.

Following are realities that we believe are important in regional management decisions. They concern the deep sandstone aquifer, from which most southeastern Wisconsin communities pump water.

Reality: The deep sandstone aquifer is disconnected from Lake Michigan by ancient flow patterns and disparate time scales.

Contrary to popular misperceptions, groundwater that regional communities pump from the deep aquifer is not from Lake Michigan, nor was it destined for Lake Michigan in a relevant time frame.

In most of our region, geology - an impermeable rock layer - restricts water from flowing down to the deep aquifer.

The groundwater our communities pump seeped under this layer at its western edge, in western Waukesha and Walworth counties and in eastern Dodge and Jefferson counties. From there, the water flowed slowly east.

Eastward flow through the deep aquifer is so slow that groundwater in eastern Waukesha County dates back to the last advance of Pleistocene ice, about 12,000 years ago, before modern-day Lake Michigan was formed.

The groundwater our communities pump today would not have reached Lake Michigan for thousands of years more.

This time scale is beyond the scope of our management. Since the Great Lakes are geologically young and will continue to change, by then Lake Michigan as we know it may no longer exist.

A related misperception holds that regional pumping is forcing Lake Michigan to recharge the deep aquifer.

While overpumping has altered deep groundwater flow, replenishment directly from Lake Michigan is insignificant. Of the 33.3 million gallons per day our region pumps from the deep aquifer, only 1.3 million gallons per day of the replacement water seeps in directly from Lake Michigan.

This is less water than the average evaporation from the lake surface in five seconds.

Our pumping is actually forcing tributaries of the Mississippi River to recharge the deep aquifer. Seventy-one percent (or 23.6 million gallons of water a day) of the water flowing into our deep aquifer is "captured baseflow," water that would naturally flow to surface lakes and streams, drawn from the Mississippi River watershed.

The remaining 29% of replacement water originates in the Lake Michigan watershed; this includes the 1.3 million gallons a day from the lake.

While groundwater and surface water are generally connected, the connection between Lake Michigan and the deep aquifer is extremely limited.

For resource planning purposes it is appropriate to treat them as separate.

Reality: Southeastern Wisconsin is not in a water quantity crisis.

Southeastern Wisconsin has abundant water resources, but by not managing them well, we have created a water quantity issue: declining levels.

This is a long-term management challenge, not an immediate crisis.

Water quality - radium contamination - is the more pressing issue for our region. Regional studies are identifying solutions for radium problems that protect both public health and the environment.

Another misperception is that water level declines in the deep aquifer can be easily remedied, for example, by shifting the City of Waukesha to Lake Michigan water.

Calculations from the U.S. Geological Survey and UWM suggest this would allow only marginal recovery of the deep aquifer, with very little improvement outside of Waukesha County.

Scenarios that allow substantial aquifer recovery within decades require all deep aquifer wells in southeastern Wisconsin and northeastern Illinois to stop pumping.

Reality: The water management challenges in southeastern Wisconsin are not unique.

There is a misperception that Waukesha and parts of New Berlin are unique because they lie outside the Lake Michigan watershed yet pump water from east of the deep groundwater divide.

But other regions, particularly northeastern Illinois, are in similar situations.

Our decisions could set precedents for Great Lakes water use in other regions.

Potential reality: Southeastern Wisconsin can become a leader in sustainable water management.

Ongoing studies by the Southeastern Wisconsin Regional Planning Commission, the Wisconsin Geological and Natural History Survey, USGS, UWM and the WATER Institute are building our understanding of regional water resources.

Simply shifting mismanagement of water resources east to Lake Michigan, west to other parts of the deep aquifer or up to the shallow aquifer is shortsighted.

Our region should apply sound science and develop long-term, sustainable alternatives for water management and land uses that affect our water resources.

Doug Cherkauer is a professor with the University of Wisconsin-Milwaukee Department of Geosciences. Nancy Frank is an associate professor at the UWM Department of Urban Planning. Tim Grundl is a professor at the UWM Department of Geosciences. Val Klump is a senior scientist for the Great Lakes WATER Institute.