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Field & Street

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The storm last February that sent waves crashing into the condos on Sheridan Road and threatened to relocate the Oak Street beach to the lobby of One Magnificent Mile made lake levels a hot political issue.

A lakefront commission appointed by the mayor last fall suddenly found itself famous. Its chairman, former alderman Martin Oberman, was quoted somewhere almost daily. The local media were full of stories. The Sun-Times even ran an editorial that informed us that the lakes rose and fell on a regular seven-year cycle. This was a major contribution in limnology, since during a century or more of careful scientific study, nobody had ever before noticed such a cycle.

Readers of Field & Street were not surprised by the sight of the surf breaking over Lake Shore Drive. I have been covering the lake levels story since 1985, when it was just an environmental issue and not a question of real estate values. Last October, I even predicted that flooding would occur during the winter, a feat of prescience that apparently escaped the notice of the Pulitzer committee.

Despite all the newspaper space and television time devoted to the problem, we still don't know what to do about it. Various solutions are offered, all of them depressingly expensive and slow to take effect. The Metropolitan Sanitary District, however, is pushing a course of action that wouldn't cost much and seems to be ready to go now. They call it diversion.

The idea seems simple. The Great Lakes are too full of water, so let's pull the plug and drain some of it out. The machinery is already in place to do this, thanks to the engineering wonders that turned the Chicago River around.

For those of you who don't remember this from grade school, the story goes like this. Until a little less than a century ago, Chicagoans used to dump their untreated sewage in the Chicago River, whence it flowed into the lake and became the city's drinking water. This was a cheap solution to the sewage problem, but it had the unfortunate side effect of turning Chicago into the cholera and typhoid capital of the Western world.

In hopes of curbing the epidemics, the city fathers devised a scheme for reversing the river's flow, rerouting it through the Sanitary and Ship Canal to the Illinois River. In order to flush all this stuff downstream, we began diverting water out of Lake Michigan. The locks and other structures that make this diversion possible can handle as much as 10,000 cubic feet of water per second, and in the early years of the system's operation, diversion sometimes went that high. But in years of low lake levels, this diversion created problems for other Great Lakes states. They took us to court, and in 1967, the U.S. Supreme Court set 3,200 cubic feet per second as the maximum allowable average diversion through the Chicago outlet. The MSD is lobbying for legislation that would overturn that decision.

There are two major objections to this project. The first is that it won't work. Increasing the diversion to 10,000 cfs, the most the system could handle, would lower the level of Lake Michigan about an inch a year for three years and a total of five inches in the course of 12 to 15 years. This is a very small difference. If the lake had been just a few inches lower last winter, we would still have had the floods.

The second objection is that diversion would create all sorts of problems downstream, including the threat of floods along the Illinois River. To understand the nature of that threat, we need to drop back a couple of million years in the history of our state. (It always helps to take the long view.)

Before the glaciers reworked the landscape of the midwest, the Mississippi River used to flow through the channel that is now the Illinois River. The Mississippi is a very big river, and the valley it carved is much larger than the modest vale a stream the size of the Illinois would require.

The outsize flood plain of the Illinois became the home of a huge system of backwater lakes and marshes that, in their pristine state, were among the most productive in North America. In 1900, 10 percent of all the freshwater fish sold commercially in the U.S. came from the Illinois River and its 378 backwater lakes, ponds, sloughs, and marshes. Boxcars of mussels were shipped from the river every year, and freshwater pearls were a major industry. Rich sportsmen came all the way from Europe to slaughter ducks along the Illinois.

Things started to fall apart after diversion began in 1900. The additional water flowing into the river raised water levels about a meter on the average. The low-water levels of summer went up as much as seven feet. Thousands of acres of bottomland forests simply drowned.

As the waters rose, the bottomland lakes grew until they covered almost twice the area they had occupied before diversion. The number of separate lakes dropped from 378 to 135 as the deepening flood combined small lakes into larger ones. Maps today still show several separate names for what are now single bodies of water. Wetland plants like duck potato were killed by the deepening water.

The steady, year-round flow also reduced the areas of mud flats. The flats develop at the margins of lakes in the low water months of summer. The plants that grow on them will be food for ducks in fall. Fewer mud flats mean less duck food.

As if diversion were not enough, our wasteful farming methods send a huge amount of sediment to the river every year. The present annual sediment load in the Illinois is over 27 million tons, enough soil to cover Chicago to a depth of one inch. Less than half this is transported by the river's sluggish current. Over 15 million tons of it is deposited in the river and its backwater lakes. The sediment is too soft to provide a suitable substrate for aquatic plants, or spawning fish, and it is steadily filling the lakes, making them less able to absorb floodwaters.

With this depressing history as background, a group of 11 scientists with the Illinois Natural History Survey prepared a report in 1980 for the U.S. Army Corps of Engineers, giving their predictions as to the effects of increasing the Chicago diversion.

They concluded that a 6,600 cfs diversion (about double the present level) would deepen the river about 1.7 feet. A 10,000 cfs diversion would deepen it from 2.4 to 2.8 feet. The results would be the drowning of yet more bottomland forest, a further increase in the depth of backwater lakes that would make it even harder for aquatic vegetation to take hold, and a major reduction in the area of mud flats. In high water years, diversion would completely eliminate mud flats in many areas.

According to the report, the populations of dabbling ducks are controlled largely by the abundance of moist soil plants, the species that colonize the mud flats when the water is low. Diversion would lead to drastic declines in populations of pintails, green-winged teal, and blue-winged teal, and it would even cut into populations of mallards, the most abundant duck in the valley.

Diversion would also harm heron populations by cutting into their shallow-water fishing areas and killing the trees they nest in.

However, all is not negative. The report does note a positive benefit for increased water flow, concluding that "Highly suitable nesting conditions provided by dead trees would probably result in increased woodpecker populations."

Fortunately, nature may confound the MSD's schemes. Our unusually dry winter and spring have already lowered lake levels, and if we have an ordinary summer, the Corps of Engineers estimates that September lake levels will be 14 inches below last September's. This is 14 times the effect that would be exerted by MSD's diversion scheme. It shows what nature can do when it sets its mind to it.

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