The water in the Great Lakes basin, immense as it may be, is a finite resource. The Great Lakes, and the human, plant, and animal communities that depend on them, are highly vulnerable. Although nearly 20 percent of the earth’s fresh surface water is on deposit in the Great Lakes, only 1 percent of the water in the basin is replenished each year. Up to 40 percent of the renewal is from groundwater seeping into the lakes. In the southern Lake Michigan region that same groundwater is steadily drying up due to overuse and wasteful practices. Declining groundwater has effects not only on the Lake Michigan ecosystem, but also, obviously, on the people who depend on it for drinking water, the farmers who irrigate their crops with it, and the industries whose operations require it.
By 2030, southeastern Wisconsin, northeastern Illinois, and northwestern Indiana are projected to see a population leap of 21 percent over the year 2000, with newcomers and natural increase coming to 2.3 million people. But there’s more: much of the growth will take place in areas least able to support it with new water withdrawal. Beyond the bounds of the Lake Michigan basin, the pivot of water availability in the region, these growth centers will have to rely mainly on groundwater. In southeastern Wisconsin, much new growth will occur to the west of the built-up land ringing Lake Michigan; in northeastern Illinois, many people will settle in the outer suburbs of Chicago; and in northwestern Indiana, the pole of growth is well to the south of the industrialized strip along the lake.
Not only is the Lake Michigan drainage divide a natural boundary, it is also a legal demarcation. Under the federal Water Resources Development Act, diversion of lake water (i.e., withdrawing water and not returning it to the Lake Michigan basin) is subject to review by the governors of the states bordering the Great Lakes. This law essentially follows the Great Lakes Charter, an agreement signed between the
Great Lakes states and Canadian provinces in 1985, under which new or increased diversions can be disallowed if they would lower lake levels, interfere with in-basin uses, or harm the Great Lakes ecosystem. An agreement to refine the way the governors and premiers evaluate proposals for new or increased lake water diversions was set forth in the Great Lakes Charter Annex 2001. Work on this decision mechanism is to be completed by 2004.
Water diversions from the Great Lakes are governed by rules that apply to all the states in our region, but Illinois is a special case. A 1967 U.S. Supreme Court decree (amended in 1980) limits Illinois’ supply of Lake Michigan water. The decree came about from a long-standing interstate dispute over the reversal of the Chicago River, early in the last century, so that it carried water (as it still does) out of Lake Michigan and eventually into the Mississippi River basin. As can be seen in Figure 3, Illinois is the only state in the region (and in the entire Great Lakes basin) permitted such a large-scale diversion. Illinois’ compliance with the diversion limits in the decree is managed under the state Level of Lake Michigan Act, which requires all users of Lake Michigan water to have an allocation permit from the Illinois Department of Natural Resources (IDNR), Office of Water Resources (OWR). Communities can apply for a Lake Michigan allocation with OWR, which evaluates the applications by a needs- balancing approach.
The bottom line following from these diversion policies is that, for the most part, communities well outside the Lake Michigan basin in Indiana and Wisconsin will probably not be able to turn to lake water as a new source for public water supply. The same is generally true of the suburbs in the inland counties of McHenry, Kane, and Will in northeastern Illinois. Using lake water would probably be possible were they able to return treated water to the lake, but doing so is generally uneconomical. Thus these communities will have to use groundwater or inland surface waters. Using inland surface waters can be problematic for two reasons. They are often a meager source of supply after allowance is made for the flow needed to support navigation and aquatic ecosystems. Because of pollution from runoff and direct discharge, moreover, the cost of treating inland surface water can be high. That leaves groundwater as the most likely source to meet future water supply needs for a large part of the region.
But the region’s aquifers (porous layers of rock below ground saturated with water) have been taxed by overuse. Water levels in the deep aquifer near the City of Waukesha, Wisconsin have been declining 7 to 10 feet per year, and the Southeastern Wisconsin Regional Planning Commission projects they will drop 125 feet by 2020. Although progress has been made, the deep sandstone aquifer in northeastern Illinois has long been in overdraft, with the rate of withdrawal exceeding the rate of recharge for the last 40 years. Around the region, communities drawing from declining deep aquifers have been hit with increased boring and pumping costs and reduced water quality. The shallow aquifers of the region, those not confined by an impervious rock layer and with, therefore, a more intimate connection to surface waters, have their own threats. For one, they are more susceptible to contamination from the surface. And since shallow aquifer recharge depends on the infiltration of rainfall in the immediate area, they are threatened by the relentless coverage of the land with parking lots and roofs, hard surfaces that stop rain from seeping into the ground.
Clearly groundwater and surface water are one resource, but in two senses: they are physically interconnected and their different users cannot enjoy them in isolation. Following Lake Michigan reallocations by OWR, more communities in northeastern Illinois could switch from groundwater to lake water. With no regard at all to political boundaries, the reallocation in turn gave a boost during the 1990s to water levels in the deep sandstone aquifer in southeastern Wisconsin. Communities dependent on lake water are dependent on groundwater as well. More precisely, they depend on the good stewardship of communities supplied by groundwater, for overuse of the aquifer threatens the groundwater seepage that partly maintains water levels in Lake Michigan.
Regional interdependence of this scope, significance, and complexity requires coordinated planning to make sure every community has the water it needs, at a price it can afford, for long into the future. The Consortium brings together the expertise of engineers, planners, scientists, and advocates from across the region. We hope to devise for decision-makers a menu of supply and management options and evaluate the consequences of the choices.
