Existing Diversions
Presently, more water is diverted into the Great Lakes basin than is diverted out.
No systematic evaluation of the ecological impacts of these diversions exists.
Some of the hydraulic changes are understood, however. The net impacts of
diversions, regulation structures, and channel dredging result in an estimated
increase in the level of Lake Superior by four inches, a lowering of the level of
Lakes Huron and Michigan by just over a foot, an increase in the level of Lake
Erie by just over an inch and a decrease in the level of Lake Ontario by about two
and a half inches.16
Although separate diversions, both the Long Lac and Ogaki diversions add
water from James Bay in Canada to Lake Superior at varying rates between
2,500 to 8,000 cfs. These diversions are used to generate hydroelectric power
and to transport pulpwood logs southward. The diversions have significant
local environmental effects on fish habitat.
The Lake Michigan Diversion at Chicago diverts on average 3,200 cfs of
Lake Michigan water to the Illinois River, which drains into the Mississippi
River. The diversion consists of three components: (1) water supply withdrawn
for domestic and industrial uses and then discharged into the Illinois River as
treated sewage; (2) runoff that once drained to Lake Michigan but is now
diverted to the Illinois River; and, (3) water diverted directly into the Illinois
River and canal system for navigation purposes, connecting the Mississippi
River to Lake Michigan.
The Welland Canal diverts water from Lake Erie to Lake Ontario for deep
draft navigation and hydroelectric power generation, bypassing the Niagara
River and Falls. The diversion also supplies water for industrial and municipal
use, including sewage dilution. During the navigation season 9,050 cfs is
diverted through Welland Canal. 7,950 cfs is diverted at other times. The
diversion has lowered the level of Lake Erie by (less than) approximately six
inches and dropped the levels in Lake Michigan and Lake Superior by about two
inches and one inch respectively. The Welland Canal has resulted in the virtual
disappearance of indigenous lake trout stocks by creating an entry point into
the upper lakes for the sea lamprey.
The New York State Barge Canal system connects the Hudson River to Lake
Ontario by diverting water from the Niagara River into Lake Ontario via a route
that connects with the Erie Canal, which connects to the Hudson River. The
diversion takes between 700 and 1,100 cfs primarily for navigation purposes.