Graphic 2
Graphic 2: Non-Consumptive Water Use in the Great Lakes Basin

Source: Great Lakes Commission

The term "groundwater" refers to the rain and snowmelt that soaks into the ground and percolates between particles of sand, soil and rock. (In contrast, "surface water" remains above ground, forming lakes, rivers and streams.) In Michigan, groundwater may infiltrate below the surface by as little as two inches per day in clay or as much as four feet per day in sand.[18]

Pools of groundwater that saturate porous rock formations or fill subterranean caverns are called "aquifers," which are tapped for wells. Groundwater also returns to the surface through springs, lake bottoms and streambeds.

Groundwater supplies are naturally “recharged” through precipitation, lakes and rivers exchange, and surface runoff.

Groundwater constitutes 98 percent of all the potable water on the Earth, according to the U.S. Geological Survey. Half the U.S. population — and 76 percent of all Michigan communities — use groundwater for drinking and most household functions. Groundwater is also a primary source for crop irrigation, food processing and some manufacturing processes.

Groundwater supplies are naturally "recharged" through precipitation (rain and snowmelt), lakes and rivers exchange, and surface runoff. Recharge rates in Michigan range from four to 20 inches per year.[19] Aquifers are also replenished "artificially" through direct injection of recycled water or from filtration basins.

There is a hydrological connection between groundwater and surface water. Lakes, rivers and streams are fed by groundwater and, conversely, lakes, rivers and streams also replenish groundwater supplies. This hydrologic interplay is complex due to variations in topography, geology and climate.

There are two categories of water use: withdrawal and consumption. "Withdrawal" refers to water drawn from surface or groundwater sources that eventually is returned to the area from where it came. "Consumption" refers to water that is withdrawn but not returned to the region. But it is important to remember that water is never actually lost, no matter what its use. Every molecule is continuously recycled through the "hydrology cycle," in which water evaporates, condenses into clouds and returns to Earth’s surface as precipitation.

In the Great Lakes basin, withdrawals comprise 95 percent of water use, consumption 5 percent. The vast majority of withdrawals — 90 percent — are from lakes, while 5 percent is withdrawn from streams and 5 percent from groundwater sources. Interestingly, Canada, with roughly a tenth of the U.S. population, accounts for 35 percent of the water withdrawals in the Great Lakes basin, compared to 65 percent by the United States. The graphic below illustrates the water withdrawals of each of the Great Lakes states and provinces.

Despite gloomy predictions of water shortages, withdrawals and consumption of Great Lakes water actually have decreased by 48 percent in the past two decades.[20] The decrease is largely a result of technological innovations, many of which improve the quality of water discharged back to the basin. All manner of water-efficient appliances — toilets, washing machines and dishwashers, for example — have come to market, along with a variety of leak-detection and pressure-control equipment. (A faucet leaking one drop per second will lose 6.6 gallons per day, or more than 2,640 gallons a year.[21])

Public data on withdrawals can also be misleading. For example, hydroelectric utilities routinely are cited as among the largest users of Great Lakes water. In fact, all but about 1 percent of the billions of gallons of water used to drive turbine generators are returned to the basin.[22] When taking the true nature of hydroelectric use into account, the volume of Great Lakes withdrawals decreases from 845 billion gallons per day to 45 billion gallons per day, a 95 percent difference.

Fears of groundwater depletion are likewise unfounded. Of the 5 percent of basin water that is "consumed," only 5 percent is groundwater.[23] Thus groundwater constitutes only one-quarter of 1 percent of the water "lost" to the Great Lakes basin.

Technological advances also are increasing water supplies the world over. From improved disinfection chemistry to fuel-cell-powered desalination plants, more efficient and affordable water-treatment methods are making more water available to more people. Worldwide, seawater-desalination plants now produce over 3.5 billion gallons of potable water each day.[24]

Lake levels do fluctuate from year to year, and even hour to hour, largely depending on precipitation, wind and air temperatures. Levels are typically lowest in winter, when runoff largely halts and masses of cold, dry air over the lakes increase evaporation. Lake levels tend to rise in summer, fed by rain and snowmelt. Over the past century, lake levels have varied by as much as five feet, as indicated in the chart below.

Graphic 3: Lake Levels Fluctuate Naturally


(Lake levels measured in number of feet above sea level.)




St. Clair



























Long-term Avg.






February 2005 Avg.






Source: U.S. Army Corps of Engineers

The primary factors influencing lake levels are variations in precipitation and temperature, not water use. Human effects on lake levels have been relatively small compared to the changes caused by natural factors.[25]

Concern over water diversion has intensified in recent years, but not because pipelines to parched regions are draining the Great Lakes — or ever will. In fact, more water is now diverted into the Great Lakes basin than is siphoned away.

A similar scare arose in the 1980s, after schemes were floated to divert Great Lakes water to raise the Mississippi and Missouri rivers, and to recharge Nevada’s Ogallala aquifer, the country’s largest. Public outrage was further aroused after Ontario’s environment ministry issued a five-year permit to a Canadian firm to ship 159 million gallons of Lake Superior water to Asia annually. The permit was rescinded, while the other proposed diversions were abandoned as technically unworkable and unaffordable.

Despite the rhetoric employed by the Granholm administration and other proponents of new water restrictions, there’s little likelihood that large diversions will become feasible in the foreseeable future. As noted by the International Joint Commission, which manages water disputes between the United States and Canada:

Future mega-diversions would present many additional engineering challenges. …[T]he costs of such projects, whether by pipeline or channel, remain enormous. Not only must capital be invested in the construction of the project, but also operating and maintenance funds must be found to support the effort. Every study of such projects has highlighted the high energy costs associated with the pumping of water over topographic barriers. Mega-diversions also require rights-of-way for their passage and security for the products being transported, which would be difficult to obtain.

Existing water diversions date back decades. The major diversions that remain operational include:

  • Lake Michigan at Chicago (1900). An average of 3,200 cubic feet per second is diverted from Lake Michigan into the Illinois and Mississippi drainage basins. This was originally devised to dilute and transport sewage to the Mississippi.

  • The New York State Barge Canal (1918). Water from the upper Niagara River at Buffalo is diverted to Lake Ontario to facilitate navigation between Lake Erie, Lake Ontario and the Erie Canal.

  • The Long Lac and Ogoki diversions (1941, 1943). Both diversions send water from Hudson Bay to Lake Superior for hydropower generation. The combined diversions average water volume of about 5,000 cubic feet per second.

  • Welland Canal diversion (1932). Water from the Lake Erie basin is diverted to the Lake Ontario basin. Originally constructed to support navigation, the diversion now facilitates hydropower generation with an annual average flow of 9,200 cubic feet per second.

Great Lakes diversions are governed by three legal instruments, all of which promote cooperative management among the eight states and two Canadian provinces in the Great Lakes basin.

The Boundary Waters Treaty between the United States and Canada, signed in 1909 by President Theodore Roosevelt andKing Edward VII, established the International Joint Commission to prevent or settle disputes over the boundary waters between the United States and Canada. Article III of the treaty requires commission approval for any diversion or obstruction that would "affect … the natural level or flow of boundary waters." (The IJC does not exercise jurisdiction over Lake Michigan because there is no common boundary between the United States and Canada.)

Diversions are also limited by the Great Lakes Charter of 1985, a cooperative agreement for lakes management among the eight states and two Canadian provinces within the basin. Under the charter, "diversions of Basin water resources will not be allowed if individually or cumulatively they would have any significant adverse impacts on lake levels, in-basin uses, and the Great Lakes Ecosystem." Nor are diversions permitted without "the consent and concurrence of all affected Great Lakes States and Provinces." In 2001 the governors and premiers of the signatory states and provinces proposed amending the charter to incorporate more stringent controls over withdrawals and diversions. The proposed amendments, known collectively as Annex 2001, require legislative enactment by each state and province. Some provisions of the proposed Annex are contained in the proposed Water Legacy Act.

At the federal level, water diversions are regulated under the Water Resources Development Act of 1986. The statute requires the approval of all Great Lakes governors for the export of water outside the basin. Whether this statute can withstand constitutional scrutiny remains a matter of debate. The U.S. Supreme Court has declared water to be an article of commerce and therefore immune from regulation that discriminates between states.