Water Resources FAQ

The MPRB has 12 public beaches. Check on Beach hours and locations and the Beach Water Quality Status before your visit.

High bacteria levels generally occur immediately after a rain event and return to normal levels within 48 hours. Avoid swimming after a rainfall when bacteria levels can be high. See the beach water resources for more information.

Minneapolis beaches are monitored between Memorial Day and Labor Day. Beaches have an advisory or are closed when monitoring results indicate an increased risk of getting sick from swimming. Blue-green advisories and beach closures are posted at the beach and on the Lake Water Quality Map. See beach water resources for more information about beach monitoring.

• What causes it? An allergic reaction to certain microscopic parasites that infect some birds, snails, and mammals.
• When does it occur? Most often after swimming on hot, still summer days.
• Symptoms: Small, irritating red welts that appear after swimming.
• Prevention: Towel dry immediately after exiting the water and shower afterwards, when possible.

Visit the Minnesota Department of Natural Resources and MPRB beach water resources for more information regarding swimmer’s itch.

There are many different opinions about what conditions make for the best swimming experience. The Lake Aesthetic and User Recreation Index (LAURI) was designed to give recreational users a source of information about conditions affecting their use of city lakes.

To ensure a healthy and enjoyable experience for swimmers, the water at the public beaches is monitored by the MPRB for E. coli, a bacteria that can be an indication of health risk for swimmers. Check the Beach Water Quality Status for up to date information throughout the summer season.

The MPRB monitors the water quality of Brownie, Bde Maka Ska, Cedar, Diamond, Grass, Harriet, Hiawatha, Isles, Loring, Nokomis, Powderhorn, Spring, and Wirth Lakes. Lakes are monitored from April through October and periodically during the winter months.

Park Board Water Quality Specialists use special equipment in the field to monitor temperature, pH, conductivity, dissolved oxygen and water clarity. Phytoplankton and zooplankton, microscopic plants and animals that are vital to the lake community, are sampled throughout the year. Samples are collected and brought to an independent lab for testing. Sample analysis includes a large profile of parameters, including alkalinity, nitrogen, chloride, chlorophyll-a, and phosphorus.

Chlorophyll-a, phosphorous and water clarity levels are used to determine a lake’s fertility, or trophic state. When these measurements are applied to a mathematical formula, called a Trophic State formula, a Trophic State Index (TSI) score from 0 to 100 is produced. Higher numbers in the TSI scores indicate that a lake is fertile. A fertile lake is a lake that has many aquatic plants, fish and algae present. Fertile lakes with high TSI scores often have water that looks like “pea soup”. Less fertile lakes, with lower TSI scores, look more like swimming pools with clear water.

Changes in lake water quality can be tracked by looking for trends in TSI scores over time. These scores are especially important for monitoring long-term trends (5-10 years). Historical trends in TSI scores are used by lake managers to assess improvement or degradation in water quality.

Minneapolis Park and Recreation Board water quality staff have monitored the stormwater that enters lakes since the late 1990s. At selected sites in the city, automated stormwater samplers are placed in storm sewers. When rainfall occurs, the samplers automatically draw water from the storm sewer, which is then collected and taken to a laboratory for testing.

The Minnesota Pollution Control Agency issued a National Pollution Discharge Elimination System (NPDES) permit that requires cities, such as Minneapolis, that operate a Municipal Separate Stormsewer System (MS4) to implement approved stormwater management activities. These activities are designed to mitigate the pollution effects of urbanization on stormwater runoff and improve the quality of stormwater entering lakes, rivers and creeks.

Stormwater retention ponds, grit chambers, and rain gardens have been installed throughout the park system. The purpose of these structures is to allow nutrients such as phosphorus and sediments to settle out of the stormwater before it enters lakes. Stormwater monitoring helps managers understand how best management practices (BMP’s) work.

Data collected over the years shows trends in water quality and how nutrients impact lakes. From this data we can determine suitable management methods and tools for improving water quality in our lakes.

Water resources monitoring serves to improve the water quality of our lakes and rivers to ensure that future generations can have clean and healthy water to use and enjoy. As a result of the data collected, efforts have been implemented to improve the water quality of city lakes. Alum treatments have been applied to some of the lakes to reduce phosphorus in the water. Aeration systems have been installed in lakes that have experienced low oxygen levels to provide better habitat for fish and reduce fish kills.

Understanding how stormwater BMP’s function allows Minneapolis to set cleaning schedules, determine when to repair BMP’s, and change future designs to increase pollutant removal.

Monitoring beaches and Webber Natural Swimming Pool for bacteria and blue-green algae protects the health of park visitors.

Data is submitted to the Minnesota Pollution Control Agency, organizations and partners that have a stake in the health of the lakes in Minneapolis, and as part of the NPDES MS4 permit annual report. See the MPRB Annual Water Resources Reports – Minneapolis Park & Recreation Board and the NPDES Annual Report – City of Minneapolis for monitoring and permit reporting.

Groundwater drawn from hand-pump wells (and a single drinking fountain) must be tested for coliform and E. Coli bacteria prior to opening for the season. If these bacteria are present, the well is chlorinated and re-tested until results are negative and the water quality is in compliance with State of Minnesota Health Code. This testing is coordinated with the City of Minneapolis.

Get more information on drinking wells from the City of Minneapolis’ Environmental Health division or call 612-673-5807 during normal business hours.

Minnesota’s waterways are threatened by aquatic invasive species (AIS). AIS are plants, animals, and pathogens that are not native to Minnesota. Once established in local waterbodies, AIS can cause economic and environmental damage as well as harm to human health.

Once an AIS is established in a new water body it is nearly impossible to eliminate. This means the most effective way to limit the impacts of AIS is to prevent their spread and establishment. The Minneapolis Park and Recreation Board (MPRB) prioritizes AIS prevention efforts to better ensure that our shared water resources can be enjoyed for years to come. Aquatic Invasive Species – Minneapolis Park & Recreation Board

Gas motors are not allowed on Minneapolis lakes except by police, MPRB staff and those permitted as safety boats for events; however, electric trolling motors are allowed. Visit the boat launch section for more information about boating on Minneapolis lakes.

Fishing is allowed on Minneapolis lakes. Visit the Minnesota DNR website for fishing regulations.

Ice houses are only allowed on Minneapolis lakes from 6 am-midnight. Portable ice houses are usually the easiest to set up and remove daily.

The Minnesota DNR has information about contaminants found in fish in specific lakes available through LakeFinder.

There are approximately 18 sites to enter and exit Minnehaha Creek between Gray’s Bay Dam and Longfellow Lagoon. The Minnehaha Creek Watershed District has canoe route maps available online.

Using salt in the winter can help keep us safe, but excess salt can also harm fish, wildlife, plants, and even humans if it contaminates drinking water. Did you know that just one teaspoon of salt can permanently pollute five gallons of water? Remember, more salt doesn’t mean more melting.

Tips to Reduce Your Salt Use and Reduce Impacts to Our Waters:

• Shovel early and often to prevent snow from turning to ice.
• Scatter salt sparingly and only where needed.
• Use sand instead of salt when it’s below 15°F.
• Sweep up leftover salt and sand to reuse later instead of letting it wash away.
• Work with Certified Smart Salting Applicators.
• Learn more: Chloride | Minnesota Pollution Control Agency

• Sweep up any fertilizer that lands on hard surfaces and put it on the grass.
• Sweep up grass clippings, leaves, litter and debris from the curb.
• Use less sand and salt on your sidewalk and driveway.
• Compost or mulch your leaves.
• Pick up after your pet.
• Dispose of motor oil or other automotive fluids properly. These materials can be taken to a Hennepin County drop off site, which is free of charge to residents.

Geese and ducks naturally feed on aquatic plants, grasses and small crustaceans. It is believed that the processed foods people feed them do not provide the range of nutrients the birds need for a healthy diet.

Feeding geese may make them more aggressive toward people. Geese who are accustomed to being handfed expect food from people and may aggressively approach people who do not have food.

Large populations of waterfowl in a small area cause soil compaction, shoreline erosion and damage to vegetation. This damage to soil and vegetation has negative impacts on the recreational and environmental quality of the area around the lake.

Concentrations of waterfowl result in a large quantity of bird droppings. Droppings contain phosphorus, which can contribute to algae growth in water. Excessive algae growth is harmful to the ecosystem and aesthetics of a lake. As algae die and decay algae use up oxygen. Low oxygen levels in a lake lead to fish kills and foul odors. Large quantities of algae in a lake are called algae “blooms” or “scums”, when there are high levels of algae, the lake becomes green, smelly and unpleasant to swim in.

Additionally, waterfowl droppings may contain bacteria and viruses. Waterfowl are hosts of the familiar parasite that causes swimmer’s itch. Feeding waterfowl, particularly around beaches and docks, may contribute to swimmer’s itch; reducing the recreational quality of these public areas.

If you are picnicking in an area where waterfowl congregate be sure to wash your hands thoroughly and make sure pets and children do not ingest waterfowl droppings.

Many cities are now banning feeding waterfowl in parks. So for the benefit of people, birds and the environment please don’t feed the waterfowl.