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Grand Portage Lake
Water Quality
One measure of a lakes health is the trophic state, which relates to the amount of algae in the water. The average summer trophic state for the last 5 years was 43 (Mesotrophic) and was determined using Secchi data. For a Deep Lowland lake, this is considered Excellent. Deep Lowland lakes stratify, or form separate layers of water, during the summer months and have watersheds greater than 4 square miles in area.
Grand Portage Lake has been monitored by volunteers since 2009. Volunteers monitor water clarity with a black and white Secchi disk. Volunteers are the source of the majority of Wisconsin's lake water quality data, and their dedication is greatly appreciated. Reports and graphs featuring data collected by volunteers, DNR staff and others can be viewed below.
Water Quality Reports and Graphs
| Station Name | Station ID | Map | Max Year | Reports |
|---|
| Grand Portage Lake - Deepest Spot | 263138 | Map | 2024 | Details |
| Grand Portage Lake NE basin Deep Hole | 10034805 | Map | 2008 | Details |