How’s the Water Minnesota? (Part 1 – Lakes)

Lakes in northern Minnesota are doing well, but most in the southern and western portions of the state are not meeting water quality standards.

For years, the Minnesota Pollution Control Agency (MPCA) has been compiling water quality data for lakes, rivers and streams, wetlands and groundwater resources around the state. Now, in a newly developed web feature, the agency is sharing this information with the public in a format that is simple and easy to understand.

Minnesota may be the “Land of 10,000 Lakes,” but the quality of these lakes varies widely from one end of the state to the other. In general, lakes in northeastern Minnesota are looking pretty good. The ecoregion is dominated by forests, wetlands and lakes, with very little farming or development, and 92% of the lakes meet water quality standards for swimming and recreation. The water is clear, algae blooms are almost non-existent, and few places have been infested by invasive species.

Meanwhile, in southern and western Minnesota, only 18% of the lakes are clean enough to swim in. Land that was once prairie has been converted to farmland, wetlands have been drained, and most farms use drain tile to quickly drain water out of the fields and into nearby waterways. Unlike the lakes up north, those in southern and western Minnesota are naturally shallow as well, so they are less resilient to pollution from excess sediment and nutrients.

Here in the metro, lake quality varies considerably. Deeper lakes fare better than shallow ones, and the lakes in less developed portions of the metro are doing better than those in cities or adjacent to farms.  About half of the metro area lakes are meeting water quality standards, while the other half suffer from algae blooms due to excess phosphorus. Invasive species are cropping up in many metro lakes because they are so heavily used. In addition, chloride levels from road salt are increasing in local lakes and streams and could become a major problem in the future.

Lakes in Washington County mirror trends in the rest of the metro. The jewels of the county like Square Lake, Big Marine and Lake Elmo are deep lakes with minimal development surrounding. In contrast, many of our shallower lakes like McKusick in Stillwater and Colby in Woodbury are inundated by runoff pollution from nearby neighborhoods. Curlyleaf pondweed and Eurasian water milfoil have taken hold in many lakes in the county, even some with otherwise good water quality.

The good news is that overall lake quality trends have stabilized over the past two decades, which means that most of the lakes in Minnesota are at least holding steady instead of getting worse. However, the MPCA has come to the frightening conclusion that, “Even if all existing laws were followed to the letter, lakes would still be subject to unacceptable levels of nutrients and other contaminants.” Furthermore, they believe that voluntary projects alone will be inadequate to protect and restore Minnesota lakes.

Happily, we have local examples in Washington County of water improvement efforts that have succeeded. During the 1990’s, the Ramsey-Washington Metro Watershed District worked hard to improve water quality in Tanner’s Lake in Oakdale.  They built stormwater treatment ponds, improved surrounding wetlands to better filter runoff pollutants, installed an alum treatment device to remove phosphorus from stormwater flowing into the lake, and restored native vegetation along some portions of the shoreline. As a result, there are less algae blooms today and the lake is now safe for swimming. Water quality in McKusick Lake has been improving as well due to multiple efforts of the Middle St. Croix Watershed Management Organization, City of Stillwater, and local residents, which include wetland improvements, shoreline projects and neighborhood raingardens. As a result, the MPCA removed McKusick from the list of impaired waters.

Elsewhere in Washington County and the metro area, several other lakes have also benefited from local government efforts to improve water quality and manage invasive species, though some of these efforts are too new still to have resulted in measurable improvements.