RESTON, VA. — Though the Great Lakes are the largest freshwater system on earth, the basin has the potential for local shortages, according to a new basin-wide water availability assessment by the U.S. Geological Survey. For example, though groundwater pumping has had relatively little effect on water in the basin as a whole, pumping in the Chicago and Milwaukee areas has caused local groundwater levels to decline as much as 1,000 feet. Moreover, if pumping were to increase as anticipated in the region, water levels in these areas are estimated to decline an additional 100 feet by 2040.
“While there is an abundance of water in the region, we may see local shortages or conflicts because water is not distributed evenly,” said Howard Reeves, USGS scientist and lead author on this assessment. “In some areas, the physical quantity of water may be limiting, and water availability in most of the Great Lakes basin will be determined by social decisions about impacts of new uses on existing users and the environment.”
Water availability in the Great Lakes basin is a balance between storage of surface water and groundwater in the system, flows of water through the system, and existing, sometimes competing, human and ecological uses of water. Water use has a relatively minor effect on regional water availability because of the large volume of water in storage, large annual flows, and abundant, high-quality groundwater. Development in the Great Lakes region also has had relatively little effect on basin-wide water availability, though surface-water diversions and pumping of groundwater have affected some flow patterns over large areas of the basin.
“This Great Lakes basin study on water availability and use provides important information for restoration and protection of regional water resources and for guiding appropriate economic development of these resources,” said Tim Eder, Great Lakes Commission executive director. “USGS information on consumptive water use also will be useful to the Great Lakes states and provinces to understand and estimate the cumulative impact of water use on regional water resources.”
Understanding the impact of climate variation on water use, lake levels, streamflow, and groundwater levels was part of this five-year investigation. Results of the study will improve the ability to forecast the balance between water supply and demand for future economic and environmental uses.
“The Great Lakes are a dynamic system responding primarily to short- and long-term variations in climate,” Reeves said. “Understanding the potential for local shortages or conflicts within this dynamic system is important for sound decision making.
USGS water availability studies like this one examine water flow and storage in surface-water and groundwater systems and compile water-use information for the region. Studies are designed to quantify the effects of past development and examine the effects of future growth on flows and storage in the system. This type of comprehensive analysis shows how competing uses and demands interact over time across a region.
Because most water-management decisions are made at the local level, this information is valuable for managers at state and local levels in making informed decisions regarding the potential effects of future water use on existing water users, aquatic ecosystems, and the public.
This study and related groundwater availability studies being conducted nationally by the USGS through the Groundwater Resources Program support the proposed Water Census for the United States. The Water Census is an initiative to provide citizens, communities, natural-resource managers, and policymakers with a clear knowledge of the status of their water resources, data on trends in water availability, and use during recent decades, and an improved ability to forecast the availability of freshwater for future human, economic, and environmental uses.
The methodology developed for the Great Lakes pilot study will be adapted to future study areas in the Colorado, Delaware, and Apalachicola-Chattahoochee-Flint River basins, as a precursor to the Department of the Interior’s WaterSMART initiative.
A USGS podcast, reports associated with this project, and additional information on USGS water availability studies in the Great Lakes Basin, are available online. Information about the USGS Groundwater Resources Program also is available online.