Turtle Lake is situated in the heart of the Chippewa National Forest and has a long-standing reputation as one of the most pristine lakes in Northern Minnesota. It is located a mile north of Marcell, MN in Itasca County.
Turtle Lake has a surface area of approximately 2126 acres. It has 556 littoral acres and a maximum depth of 137 feet. It has 26 miles of shoreline, about two-thirds of which is privately owned. The other third of its shoreline is unadulterated federal, state, and county land. The MN DNR maintains a public access on the northeast side of Turtle Lake.
The lake is part of the Big Fork River watershed. It has three inlets: two major ones on the far north end of the lake and one minor one in Moose Bay. Turtle Lake’s only outlet—the Turtle River—flows out of Alex Bay to the Bowstring River, the Bigfork River, and finally the Rainy River where it forms the MN/Canada border on its way to Hudson Bay.
Water Quality
Turtle Lake is an oligotrophic lake with a trophic state index (TSI) of 36. TSI quantifies the water clarity, phosphorus, and chlorophyll-a level of lake water. When phosphorus increases, algae produce more chlorophyll-a. As algae numbers increase, water clarity decreases.
Several times a year, TLA volunteers monitor the health of our lake by measuring water clarity and collecting water samples.
Secchi Depth To measure water clarity, a white secchi disk is lowered into the lake until it is no longer visible from the surface. Turtle Lake has significantly clearer water than most lakes in the region, with an average secchi depth of 17.3 feet in 2019.
Phosphorus Levels and Chlorophyll-a Levels Water samples are collected by volunteers and sent to RMB Environmental Labs to test for these and other indicators of lake health. Average 2019 readings are as follows:
Phosphorus level: 8.5 ug/L (expected range for our region is 14–27 ug/L)
Chlorophyll-a level: 2.3 ug/L (expected range for our region is 4–10 ug/L)
Additional reading
Blue Water Scientific Plant and AIS Survey Results (2020 Report)
MN Pollution Control Agency (Water quality readings)
Lake Level
The Turtle Lake Association has hosted public meetings with property owners, the MN DNR, and the Chippewa National Forest Service to determine lake levels that will best meet the needs of the majority of Turtle Lake owners while remaining environmentally sound.
Using this input and years of Turtle Lake hydrology information, the MN DNR has recommended that we maintain a lake level between 1351.0 and 1351.8 feet, a range of 9.6 inches.
A lake level committee exists to try to keep the lake level within the DNR-recommended range with as little micromanaging as possible.
Because the level of Turtle Lake is somewhat controlled by a beaver dam at the outflow, the lake level committee occasionally removes just enough material from the dam to maintain the lake level within the 9.6-inch range. Please keep in mind that the water level will continue to fluctuate within that range based on precipitation.
