TRAVERSE CITY, Mich. (AP) -- Despite having more fresh water than anywhere else in the world, the Great Lakes region could experience shortages in some locations because of climate shifts or surging demand, a federal analysis says.
The five-year study by the U.S. Geological Survey, obtained by The Associated Press ahead of its scheduled release Monday, describes the Great Lakes as an aquatic treasure trove. The lakes themselves have 6 quadrillion gallons -- enough to spread a foot-deep layer across North America, South America and Africa -- and the volume of groundwater surpasses that of Lake Huron.
Yet groundwater levels have plummeted about 1,000 feet in the Chicago-Milwaukee metro area because of pumping for municipal supplies and could drop an additional 100 feet over the next three decades if withdrawal rates jump as expected, the report says. The Milwaukee suburb of Waukesha, its deep wells contaminated with radium, is seeking permission to tap Lake Michigan under a compact signed by the region's eight states in 2005.
The report doesn't identify other potential problem areas, but lead author Howard W. Reeves said local officials should become familiar with data about supplies close to home and use it to guide long-range planning for development and water use.
"The availability of water resources isn't uniform over the whole basin, and things change with time," said Reeves, a USGS hydrologist based in Lansing. "In some areas, there's plenty and a big use wouldn't have a negative impact. In other places that's not the case. We need to be trying to understand those situations, rather than assuming the water will always be available everywhere."
Just 1 percent of the lakes' water is replenished annually through runoff and precipitation, and vast amounts are removed for agriculture, industry, drinking and other uses. Still, the overall supply is so huge that withdrawals have had little effect on the Great Lakes system, the report said.
With a few notable exceptions, urban and suburban development also has not put a serious dent in supplies, although surface water diversions and groundwater pumping have affected some flow patterns over large areas. The 2.1 billion gallons that Chicago diverts from Lake Michigan daily has lowered Lakes Michigan and Huron by about 2.5 inches.
Weather and climate, on the other hand, have significant effects on groundwater and lake levels and stream flow rates, Reeves said. Declining lake levels over much of the past decade resulted largely from drought and warming temperatures that limited winter ice cover and boosted evaporation.
Marc Smith, a policy analyst with the National Wildlife Federation's regional office in Ann Arbor, said the importance of sound water use should not be underestimated as the Great Lakes states and the Canadian provinces of Ontario and Quebec develop conservation plans and permitting systems for large withdrawals as required under the 2005 compact.
"We live in a very water-rich area and it's easy for folks to look at this vast resource and think there's no way we can deplete it, we don't have to worry about conservation," Smith said. "That would be a terrible mistake."
Congress in 2002 ordered the USGS to develop a nationwide assessment of fresh water supplies and usage amid concern about shortages in the next century. The Great Lakes report is the first step. Methods used in the study will be adapted for analyses in the Colorado, Delaware, and Apalachicola-Chattahoochee-Flint River basins, the agency said.