Tired of algae in the lake? Then lower the phosphorus levels with Lake Steward

These hot and muggy dog days are perfect lake weather, perfect for swimming in the lake, waterskiing and other water sports. Unfortunately, it  is also becoming primetime for the algae blooms that can spread across the lakes we love and make swimming, skiing and watersports impossible. There are many different types of algae, from the beneficial to the toxic blue green, and while contact with blue green algae can result in rashes, illness or even death, particularly for pets, even benign algae makes swimming unpleasant. 

Data supports what many longtime lake residents suspect; algae blooms are starting earlier in the summer, growing larger and lasting later into the year. Toxic blue green algae blooms are also on the rise in our lakes.

Shoreline property owners do have some level of control. By bringing together local partners, organizing the larger community and taking direct action on their own shorelines, lakeshore owners can reduce runoff pollution into the lake and limit the growth of algae. 

Minnesota’s lakes are fertile and have most of the nutrients plants and algae need to thrive. The exception is phosphorus. Phosphorus is a “limiting nutrient” in Minnesota.

Reduce phosphorus levels in a lake, and you will reduce algae in that lake.

Back in the 1970s, after passage of  the Clean Water Act, most of the large and specific sources of pollution were shut down. Factories and slaughterhouses stopped dumping waste into our rivers and lakes. Towns no longer dumped raw sewage into the nearest waterbody. This is known as “point source” pollution. For decades after passage of the clean water act water quality improved across the country.

Then, after decades of improvement, water quality began to decline again. Today 56% of Minnesota’s surface waters are listed as impaired. Pollution no longer comes from a single source, but myriad sources, small, discrete and dispersed. This is called “nonpoint source” pollution, and it comes in varying degrees from many of the properties in a watershed as rainwater and snowmelt flows over farm fields, pavement, roofs and lawns and wends its way to the nearest lake or a river without soaking into the ground. To prevent this dispersed pollution, landowners must keep water where it lands and not let it run off their properties. In order to save our lakes each of us must get the rainwater and snowmelt that falls on our land to infiltrate instead of running off. Our gutters and pavement and lawns all prevent infiltration and allow water to flow across the landscape, picking up phosphorus and other chemicals as it travels, and carrying it to our lakes and rivers. The need to prevent runoff is particularly acute on lakeshore properties.

Soils in Minnesota contain phosphorus as does the atmosphere. Rain and snow collects atmospheric phosphorus as it falls and picks up more as it moves across the landscape. On a natural shoreline, where rainfall can soak into the ground, the phosphorus-starved roots of native plants, trees and shrubs take up most of this phosphorus before it enters the lake.

Minnersota’s changing climate makes the problem worse. Minnesota is getting more rain than in the past, and it is coming in larger and more intense rain events.

Minnesota Lakes and Rivers Advocates (MLR’s) Lake Steward Program teaches and supports shoreline owners to better manage rain and snowmelt so that they can help restore water quality in the lakes they love. The Lake Steward program trains lake association volunteers and provides educational materials so that they can assist their neighbors as they commit to becoming a Lake Steward. Lake Steward helps lake associations engage local government units to support this work. A shoreline managed using Lake Steward strategies contributes seven to nine times less runoff pollution than a “lawn to lake” shoreline without Lake Steward mitigations.

Roger Rauschendorfer has spent years doing water quality analysis on Lake Augusta in Wright County. Lately he has recorded troubling trends. “We had a series of two and three inch rains this spring and our phosphorus content (in Lake Augusta) doubled.” This is when Roger decided to become a Lake Steward and to promote the program to other lakeshore owners on Lake Augusta. He worked with the local watershed district to do a shoreline restoration. Minnesota Native Landscapes provided deep rooted native plants and the county helped with matching grants and expertise.

MLR’s Lake Steward Program works to prevent phosphorus in lakes by encouraging lake associations and their members to restore their shorelines to a native landscape, curbing pollution through the inclusion of a natural buffer to excess rainwater runoff, installing permeable pavements and walkways and directing gutters to rain gardens or swales. Phosphorus contamination cannot be avoided entirely; even totally natural shoreline contributes a median of 0.03 pounds of phosphorus to a lake over the summer. A lawn-to-lake property, however, contributes an average of  0.2 pounds of total phosphorus. One pound of phosphorus in a lake or river can produce 500 pounds of algae. 

Each lake in Minnesota has limits for the amount of phosphorus it can cycle before problems arise – a phosphorus sensitivity level. The MN DNR has determined the phosphorus sensitivity level for over 800 lakes in Minnesota, and described the amount of excess phosphorus entering each lake above this level. By lowering the amount of excess phosphorus entering the lake to below this phosphorus reduction goal, lake shore property owners can protect water quality and reduce the size and duration of algae blooms.

Knowing the phosphorus sensitivity level for a lake and the phosphorus reduction goal establishes a focal point and achievable goal for local water efforts. Local governmental resource managers like a watershed district, soil and water conservation district or county land office can work with a lake association to identify all phosphorus sources to a lake; upstream sources, residential storm sewers, agricultural runoff and shoreline management. Together they can begin on-the-ground projects to sequester runoff; settling ponds, stream enhancements and wetland restorations, and begin to mitigate the largest sources. 

Lakeshores are also a significant source of runoff pollution and contribute to higher phosphorus levels in our waters. Shoreline management will be a key component of any phosphorus reduction campaign. The  Lake Steward program will help focus the attention of lakeshore owners to this issue, and teach them how to convert lawn to lake shoreline lots to buffered lots in order to achieve a lake’s phosphorus reduction goal. When lakeshore owners begin to restore shorelines, this signals to local governments a public commitment to water quality and can drive further action by them. Shoreline restorations are usually a critical strategy to meet phosphorus reduction goals. Lake Steward gives shoreline owners a set of actions they can take to advance the larger goal of lake restoration and phosphorus reduction. Like a thermometer graph for a fundraising campaign, setting a clear goal with a well defined outcome brings a community together and increases energy around a shared effort.

The simple truth is that if each of us does not work to protect water then water quality will continue to decline. No government agency at any level can do the work alone. But by forming community partnerships around a clear goal, pooling resources, time, constituencies, expertise and money, local lake preservation can be achieved. Lake Steward is a great first step to educating lake association members to the need and then giving them concrete actions they can take to achieve a rational phosphorus reduction goal as they build a base of public support for larger, more complex and more expensive mitigations.
Minnesota Lakes and Rivers Advocates protects Minnesota’s lake and river heritage for current and future generations by forging powerful links among lakes, lake advocates, and policy makers. Want to get involved in the Lake Steward Program? Contact MLR’s Program Manager, lily@mnlakesandrivers.org