Story URL: http://news.medill.northwestern.edu/chicago/news.aspx?id=214087
Story Retrieval Date: 3/29/2015 7:27:43 AM CST
Contrary to recent rumors, it is simply impossible for the polluted Chicago River to naturally reverse course and flow back into Lake Michigan, according to the Metropolitan Water Reclamation District.
Last week, reports suggested that near record low Great Lakes levels could cause the Chicago River, which currently flows away from the lake, to naturally change direction due to gravity. However, the reports failed to account for the reengineered river flow and the lock and dam system that separates the river from the lake to prevent this very situation.
“It is not possible for a natural reversal to ever occur,” said David St. Pierre, executive director of the MWRD. “The water levels in the Chicago Area Waterways are controlled by MWRD-operated gate structures at the lake and at the discharge point, and as a result, the structures do not allow for a natural reversal of the river.”
The MWRD should know: over a century ago, the agency orchestrated a massive engineering feat to reverse the river, which initially did flow into the lake.
In recent reports, the current drought has been blamed as the culprit for falling water levels in Lake Michigan. According to Phil Willink, senior research biologist at the Shedd Aquarium, the problem could extend beyond current weather patterns.
“Based on projections, Lake Michigan could drop another inch or two this year and that really depends on precipitation,” Willink said. “If we continue to have drought conditions over another year or two, we will be in a crunch situation where decisions have to be made.”
Willink said that manipulating the river to prevent reversal could force policymakers to weigh factors such as biodiversity, sanitation and shipping routes against one another.
“If we’re not replenishing the river with a lot of Lake Michigan water, water quality in the river will decline and will lose a lot of oxygen and a lot of things living there will die,” Willink said. “People are going to have to make a choice. Do we let the things in the river die and keep the shipping going and the sanitation going, or do we lower the river and have it go another way?”
In 1900, the MWRD and Army Corps constructed a system of canal locks to reverse the flow of the Chicago River. This directed the water into the newly-formed Chicago Sanitary and Ship Canal and then into the Mississippi River basin. The enormous public works project keeps wastewater out of Lake Michigan, the city’s primary source of drinking water.
The system, still in place today, controls the water levels and flow of area waterways. The locks can be opened or closed as needed for cargo and tourist traffic.
When the locks are opened to accommodate these vessels, there is a small exchange of water between the lake and the river, said Roy Deda, deputy district engineer for project management for the Chicago District U.S. Army Corps of Engineers, which works closely with MWRD.
The locks are also opened to prevent and relieve stormwater flooding
from heavy rainfalls, which occur about once a year.
“It’s not a good thing when it does happen, but the volume of water being released into the lake is dwarfed by the amount in the lake,” said Josh Ellis, program director at the Metropolitan Planning Council.
MWRD officials stated there is no reason to expect water quality problems in Lake Michigan due to low lake levels.
“There have been inaccurate reports that the river system is 70 percent sewage," St. Pierre said. “Sewage is what comes in to the seven MWRD treatment plants. Clean, treated water is the product the MWRD releases to the Chicago Area Waterways.”
The water is not disinfected as yet, however, though plans are in place to take that step.
Mandy Burrell Booth, communications director at the Metropolitan Planning Council, said the organization agrees “100 percent” with MWRD’s position regarding the reports of potential river flow reversal.
According to Ellis, only one situation would cause the river to reverse and spill into Lake Michigan: if MWRD and the Army Corps accidentally just left the locks open. Then, the river levels would be higher than the lake levels and reversal would be possible.
“However, that’s not going to happen,” he said. “They are not going to stop paying attention.”