The Great Lakes Commission has conducted a preliminary examination of water use data (1987–93) in the Great Lakes basin. Water uses comprise two categories: consumptive uses and removals. Close to 90 percent of withdrawals are taken from the lakes themselves, with the remaining 10 percent coming from tributary streams and groundwater sources. An estimated 5 percent of the water withdrawn from the Great Lakes is consumed and is therefore lost to the basin. In 1993, consumptive use in the Great Lakes basin was estimated to be 116 cubic meters per second (4,096 cubic feet per second) as compared to withdrawals of about 2,493 cubic meters per second (88,000 cubic feet per second). The 1993 consumptive use in the Great Lakes basin can be summarized as follows:

• By country: In total, consumptive use is 36 percent for Canada and 64 percent for the United States, with per capita consumptive use being approximately equal for the two countries.

• By jurisdiction: The largest nonconsumptive water user is Ontario at 29 percent followed by Michigan at 22 percent; Wisconsin at 21 percent; Indiana at 7 percent; New York, Quebec, and Ohio at 6 percent each; Minnesota at 2 percent; and Pennsylvania and Illinois at less than 1 percent each.

• As identified in the adjacent figure the largest Great Lakes water use is irrigation followed by public water supply, industrial use, fossil fuel, thermoelectric and nuclear thermoelectric uses. The adjacent figure identifies current water uses in the Great Lakes basin, including water withdrawals and consumptive uses.

Based on a very preliminary analysis, growth in withdrawals and consumptive uses in the basin appears to have slowed. In the International Joint Commission's 1985 Great Lakes Diversions and Consumptive Uses report, consumptive use in the Great Lakes Basin was estimated to be in a range of about 82 cubic meters per second (2,900 cubic feet per second). This is a significant reduction from the 1980 estimates of 159 cubic meters per second (5,600 cubic feet per second). Information from the Regional Water Use Database suggests that consumptive use in 1993 was still near the middle of that range, which would be consistent with a more general leveling off of water use in North America.

The International Joint Commission developed tentative projections into trends in water use and their impact on potential future water demands. These projections were derived from a simple extension of trends established over the previous decade. Results, presented below, extend to the years 2020–21. The Commission cautions that projections beyond two decades are highly speculative.

• Thermoelectric Power Use - In the United States, Great Lakes withdrawals have remained relatively constant since 1985 and are expected to remain near their current levels for the next few decades. In Canada, modest increases are expected to continue along with population and economic growth.

• Industrial and Commercial Use - In the United States, industrial and commercial Great Lakes water use has declined. A similar trend is evident in Ontario. Expected use to gradually decline through 2020.

• Domestic and Public Use - In the United States, Great Lakes water use for domestic and public purposes generally increased from 1960 to 1995 and is expected to climb gradually through 2020. Because of aggressive water-conservation efforts in Ontario, a modest downward trend established in recent years is expected to continue.

• Agriculture - In the United States, Great Lakes water used for agriculture increased fairly steadily from 1960 to 1995. In Canada, the rate of increase was somewhat larger. Combined projections indicate a significant increase by 2020.

• Total Water Use - If current trends continue, total water use in the Canadian portion of the basin is expected to increase by close to 20 percent between 1996 and 2021. A decrease of about 2 percent is expected in the United States. portion of the basin between 1995 and 2020, although the United States use is expected to begin rising again after that time. The combined projections indicate a modest increase of about 5 percent for the entire Great Lakes Basin between 1995-96 and 2020-21.

Source:

Great Lakes Trends: Into the New Millennium, May 2000 prepared by Office of the Great Lakes, Michigan Department of Environmental Quality.

International Joint Commission:  Protection of the Waters of the Great Lakes - Interim Report to the Governments of Canada and the United States. 1999.