Lake Water Resources

As the City of Lakes, Minneapolis is known for its ample and beautiful lakes. Without a dedicated effort to preserve and protect these urban waters, our lakes would not be the valuable resources that they are today. The Minneapolis Park & Recreation Board’s (MPRB) lake water quality monitoring program was implemented in 1991 as part of a diagnostic study for the Chain of Lakes Clean Water Partnership. We currently monitor 13 lakes within the City of Minneapolis:

Long-term stormwater management is one key to keeping lake water quality suitable for recreation and for sustaining plants and wildlife. MPRB is seeking dedicated funding to invest in stormwater management and protect Minneapolis lakes.

Lake Conditions

We make some monitoring data available throughout the season so you have an idea of lake conditions:

Updated Secchi disk readings indicate the current clarity of each lake.
We monitor beaches during the summer to determine if there are any health risks to swimmers. Weekly data indicates:
- Open/closed status of the beaches
- E. coli levels
- Microcystin levels
- Current water temperature

Blue-Green Algae

Algae are tiny, harmless organisms that are natural and common in freshwater. Blue-green algae, which is present in lakes throughout Minnesota, are not algae at all, but a type of bacteria called cyanobacteria. In the right conditions they can grow quickly to form “blooms”. Sometimes blue-green algae can produce cyanotoxins that can make humans and animals sick. Before getting in the water, always take an overall look at water conditions and do not enter the water if you see blue-green algae. Blue-green algae blooms and scum can move with the wind, so blooms will shift around the lake depending on weather conditions.

Learn how to recognize and respond to blue-green algae.

Despite its name, blue-green algae may not always be blue-green. It may also be reddish-purple or brown. Blue-green algae causes the water to be murky.

When environmental conditions are just right, blue-green algae can grow very quickly. Most species are buoyant and will float to the surface, where they form scum layers or floating mats.

Do not swallow or go into water that looks like "pea soup", green or blue paint, or that has a scum layer or puffy blobs floating on the surface.
Keep children and pets out of blue-green algae scum.

For more information about blue-green algae Minnesota Department of Health: Harmful Algal Blooms (HABs)

Filamentous Algae

Filamentous algae are single cell organisms that grow in long strands, or filaments. These filaments can intertwine to form thick mats which float to the surface of lakes and ponds. Filamentous algae can often be confused with blue-green algae, a cyanobacteria that can be harmful. Filamentous algae is not harmful and does not produce toxins. Learn more about filamentous algae and how to tell it apart from blue-green algae.

Aquatic Invasive Species

Aquatic invasive species are often the most visible sign of change in lakes, and many problem species are very difficult to remove or even limit. We carefully monitor these species in cooperation with various state agencies and work to limit their spread where possible.

Water Clarity

About Secchi Disk Readings

To measure water transparency with a Secchi disk, the disk is lowered from the shaded side of a boat until it cannot be seen. The depth of the water is recorded at the point where the disk reappears upon raising it from its original depth beyond visibility. It is important to remember that the Secchi measurement is a simple, approximate measurement of water clarity and can be influenced by various factors such as time of day, reader’s eyesight, water color and suspended particles in the water. Therefore, Secchi disk readings should be used as a comparative tool to determine trends between lakes and over time.

Increased water clarity may be due to reduced nutrient inputs, seasonal algal cycles, decreased sediment inputs, and zooplankton grazing on algae.
Decreased water clarity may be due to large algal blooms, increased soil erosion inputs, wind circulation of sediments and nutrients, stormwater inputs, or a decrease in zooplankton.

Secchi readings for the lakes are done during the regular lake sampling schedule, with some lakes sampled every other year. Current Secchi readings taken during lake sampling can be found on the Lake Water Quality Map.

LAURI

Lake Aesthetic and User Recreation Index (LAURI)

Citywide LAURI measurements for 2025. Aesthetics - Excellent, Water Clarity - Good, Public Health - Good, Habitat Quality Excellent, Recreation Access - Excellent.

The Lake Aesthetic and User Recreation Index (LAURI) was designed to give recreational users an easily understandable graphical source of information about conditions affecting their use of city lakes. The goal is to have an accurate, science based and easily understandable recreational indicator for the public. The LAURI has the five following indices: aesthetic considerations, water clarity, public health, habitat quality, and recreational access. For each of the five indices, the LAURI calculates a value that is then considered poor, good, or excellent.

Click here to view more information on LAURI

Monitoring

Long-term monitoring is important because lakes can change from year to year due to wet or dry weather and we can only see trends when we put years of data together. Analysis of this data tells us if the water quality is improving or not.

View the MPRB Water Resources Report for detailed annual monitoring data, data collection methods, and more.