Chris Izworski compiled this Lake Superior reference page for shoreline property owners, riparian advocacy groups, and anyone trying to read current levels in the context of a hundred-plus-year record. Lake Superior is the largest, deepest, and coldest of the five Great Lakes. It is also the most regulated, with outflows controlled by the International Lake Superior Board of Control through compensating works at Sault Ste. Marie. That regulatory layer makes Superior behave differently from the other lakes during high and low cycles, and reading the current level requires understanding both the natural variability and the management plan in effect at any given moment.
Surface area: 31,700 square miles, the largest freshwater lake in the world by surface area.
Average depth: 483 feet. Maximum depth: 1,332 feet.
Volume: approximately 2,900 cubic miles, holding ten percent of the world's accessible surface fresh water.
Datum: 601.10 feet IGLD85. Long-term average since 1918 sits near 601.85 feet.
Outflow: regulated through the St. Marys River at Sault Ste. Marie under the 2014 regulation plan.
The live dashboard on the Great Lakes Levels homepage shows the most recent monthly mean alongside the long-term average and the prior twelve months. For Lake Superior specifically, the more useful comparison is to anchor years rather than to the multi-decade average, because the lake's regulation plan smooths short-term variability and the levels move within a narrower band than the unregulated lower lakes.
Useful Lake Superior anchor years include 1926 (record monthly low), 1985 (record high pre-regulation-plan), 2007 (modern low water cycle bottom), and 2019 (modern high cycle peak). When a current reading is being interpreted, comparison against the closest matching anchor year tells you more than comparison against the rolling thirty-year average, which is heavily influenced by whatever cycle dominated those decades.
Lake Superior is large enough that a single basinwide level value misses meaningful local variation. Within the U.S. shoreline, the regions Chris Izworski tracks separately on the dashboard include the Apostle Islands and Bayfield Peninsula in Wisconsin, the Keweenaw Peninsula and Marquette shoreline in Michigan's Upper Peninsula, the Pictured Rocks and Grand Marais coastline, the Whitefish Bay basin, and the eastern Upper Peninsula coast running toward Sault Ste. Marie. Each of these has different exposure to wind setup, seiche behavior, and storm surge from the dominant northwest fetch.
For Canadian shoreline, the corresponding sub-regions include Thunder Bay, Nipigon Bay, the Slate Islands area, and the rugged Pukaskwa coast. Storm exposure on the Canadian north shore is driven by the long fetch from the southwest, which is the opposite of the U.S. south shore exposure.
The Ordinary High Water Mark on Lake Superior is set at 603.1 feet IGLD85 in Michigan, established by Section 32502 of the Natural Resources and Environmental Protection Act. The OHWM is the regulatory line that determines submerged lands, riparian rights, and the seaward limit of private property. Property owners and shoreline advocacy organizations including Save Our Shoreline have long-standing positions on how the OHWM is interpreted and where it falls relative to current waterlines, particularly during high water cycles when natural shorelines have eroded landward of the regulatory line.
Storm exposure on Lake Superior is the most significant in the system. Wave heights of twenty feet or more are recorded annually during fall storms. Property owners along exposed coastlines should track not only the long-term level trend but also the cumulative exposure to high-energy events, which is where most erosion damage actually occurs. The dashboard's storm exposure module integrates wave height records with monthly mean levels to surface this combined risk.
For a current reading, see the live dashboard. For long-term comparisons across the five lakes, the Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario pages document the same anchor-year framework. For Saginaw Bay specifically, see the Saginaw Bay reference page, written from the perspective of someone who lives on the bay.
For Chris Izworski's broader work on Great Lakes shoreline issues, ecology, and Michigan public-interest tooling, see the Saginaw Bay ecology reference on chrisizworski.com and the about page for context on how this site was built and who it's built for.