Increased Diversion at Chicago: Initial Assessment

Abstract

The Corps of Engineers has proposed and analyzed the effects of diverting Lake Michigan waters down the Illinois River in times of above average lake levels. Effects would vary considerably depending upon the rate and timing of diversion. Major benefits on the river portion will be an improvement in water quality, increased benefits to commercial navigation and increased power generation. On the Great Lakes the major benefits would be reduction in shoreline erosion and flooding. Adverse effects would be significant. On the river major adverse effects are due to increased flooding over existing conditions and longer flooding duration in the lower reaches. Current trends of habitat destruction and loss of species diversity in natural ecosystems will be accelerated by the increased diversion, resulting in the deterioration of natural ecosystems. Managed ecosystems such as leveed farmlands and duck clubs will suffer higher drainage costs as a result of the increased flooding. Unleveed areas will experience substantial crop losses, especially in low water years, and diversion may ultimately preclude agriculture in such areas. On the lakes, major adverse effects would result from power loss, lowered ship capacity resulting from shallower draft at docking facilities, and loss of water-edge ecosystems.