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Restoration of Aquatic Ecosystems: Science, Technology, and Public Policy
Claire L. Schelske and Stephen R. Carpenter
Restoration measures have been instituted as the result of a series of environmental problems that have occurred in Lake Michigan (Figure A.1) since the drainage basin was settled by Europeans. In the late nineteenth century, drinking water for the city of Chicago was contaminated with human and other wastes. In 1900, sewage was diverted from the lake to the Mississippi River drainage via the newly constructed Chicago Sanitary and Ship Canal. The diversion controlled waterborne vectors for diseases, including typhoid and cholera. More recently, water quality problems in the lake have resulted from accelerated nutrient enrichment. The fisheries of the lake have also been affected by changes that followed European settlement. Populations of commercially important fish have been eliminated sequentially from the combined effects of environmental degradation, overfishing, and eutrophication (Christie, 1974). In addition, the fish community has been altered by introductions and invasions of exotic species. Potentially toxic chlorinated hydrocarbons, which have been manufactured in the last four or five decades, have entered the food chain and now pose serious problems for the fish community.
Historical management strategies for Lake Michigan illustrate some of the consequences of attempts to restore degraded water quality and fishery resources. The main lesson is that management is imperfect and can remediate only some problems. Therefore, whenever possible, we should try to preserve natural systems and avoid having to restore them. Five examples can be cited. First, seriously contaminated water supplies were restored at great expense in 1900 by diverting sewage from Lake Michigan to a river basin (see Illinois River case study, Appendix A). (The cost of constructing the Chicago Sanitary and Ship Canal was $36 million; this was the largest channelization project prior to construction of the Panama Canal.)
Second, although problems of nutrient enrichment were alleviated initially by the Chicago sewage diversion, continued nutrient loading from sewage probably would have had severe environmental impacts