How Are We Using Great Lakes Water and Groundwater?

Above: Watershed art by Glenn Wolff.

By Bob Otwell, FLOW Board member

A Great Lakes water use report recently released by the Great Lakes Commission provides an important snapshot of the kinds and volumes of water withdrawals in the region.

Annual Report of the Great Lakes Regional Water Use Database – 2021 data-Jan 2023

The report found that an average 37.5 billion gallons of water per day were withdrawn from the Great Lakes Basin in 2021. Most of this water (71%) was utilized for cooling of power plants. The next highest use was 14% for public water supply. The primary source for both of these two categories is Great Lakes surface water.

The report found that an average 37.5 billion gallons of water per day were withdrawn from the Great Lakes Basin in 2021. Most of this water (71%) was utilized for cooling of power plants.

The report included water use data from eight Great Lakes-St. Lawrence River states (Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania and Wisconsin), and two Canadian provinces (Ontario and Quebec).

Water use was presented from three sources; Great Lakes surface water, other surface water (rivers and lakes), and groundwater. Levels in the Great Lakes have ranged from an all-time low to all-time high over the past decade. Our societal usage of Great Lakes surface water has negligible effect on their levels. Levels in the Great Lakes are primarily influenced by precipitation and evaporation.

Water use was presented from three sources; Great Lakes surface water, other surface water (rivers and lakes), and groundwater.

Groundwater levels have been dropping in some parts of Michigan in recent decades due to overuse. Groundwater was only about 3% of total basin water use. Groundwater withdrawals occurred mostly in three categories: public water supply (41%), industrial (26%), and irrigation (23%). Of these three, irrigation had by far the highest consumptive use (88%) of total use, whereas public water supply and industrial consumptive use comprised just over 10% of total use. Consumptive use refers to the portion of the water withdrawn or withheld from the basin that is lost, or otherwise not returned, to the basin due to evaporation, incorporation into products, or other processes.

Groundwater levels have been dropping in some parts of Michigan in recent decades due to overuse.

Ontario has the largest land area in the basin, and the largest total withdrawal of the 10 jurisdictions. Michigan has the second largest land area but has the largest groundwater withdrawal volume of all states and provinces, 44% of the total. In Michigan, 39% of all groundwater withdrawal is for irrigation.

There are areas in Michigan, like Ottawa County, where groundwater demands exceed sustainable groundwater supply. In Southwest Michigan, the acreage irrigated for agricutlure has increased over the past decade. As we start to use more groundwater in Michigan, care should be taken to improve monitoring and reporting of groundwater levels, along with groundwater usage, on an annual basis.

There are areas in Michigan, like Ottawa County, where groundwater demands exceed sustainable groundwater supply.

The state legislature has recently approved funding for some of this work. The funding provides an educational program to increase agricultural water use efficiency. In addition, a database is being created to help with hydrogeologic data collection and modeling and increasing the availability of existing data in a common format. In 2022, the Michigan Groundwater Table convened by FLOW unanimously approved and encouraged the legislature to embrace these recommendations.

About the Author: Bob Otwell, who has served on FLOW’s Board of Directors since 2013, is a hydrologist, civil engineer, and founder of Otwell Mawby engineering in Traverse City, Michigan.