Water shortages could hit Great Lakes

Climate change and heavy demand could result in water shortages in the Great Lakes region, a new report from the U.S. Geological Survey warns.

The Associated Press reports:

Just 1 per cent 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, [USGS hydrologist Howard W. 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/

There are examples of human use impacting water availability.

Groundwater pumping in the Chicago and Milwaukee areas has caused local groundwater levels to decline as much as 1,000 feet, and if current trends continue the groundwater level could drop another 100 feet in the next 30 years, the report found.

The USGS analysis combined groundwater and surface-water modeling and found that a single pumping well can affect a nearby stream, even to the point of drying the stream during some of the year.