Any geography student who's viewed a map of the United States has surely marveled at the vast expanse of the nation's Great Lakes, which contain nearly 20 percent of the Earth's surface water. To stand on the shore of any one of these freshwater inland seas—Superior, Michigan, Huron, Erie, or Ontario—is to gaze across boundless waters to a distant horizon.

NOAA's Office for Coastal Management provides a unique perspective on these impressive water bodies with its Lake Level Viewer for the U.S. Great Lakes. Funded by the President's Great Lakes Restoration Initiative, the online viewer displays variations in lake levels ranging from six feet above and below the long-term average, and helps users visualize the impacts of lake-level fluctuations on shorelines and coastal areas.

The viewer is designed to help communities make smart planning decisions for zoning restrictions and infrastructure (e.g., marinas, intake pipes), encourage sustainability, and restore and conserve natural habitats. Regional stakeholders including resource planners, regulatory agencies, and conservation groups helped design and test the viewer, which complements NOAA's Great Lakes Environmental Research Laboratory's Water Level Dashboard.

Water levels are shown as they would appear during calm conditions, and the data and maps illustrate the scale of potential flooding or land exposure at a given water level (not the exact location). City planners, floodplain managers, tribes, business owners, and other users can download the data, and may also access services for more in-depth analyses.