Minneapolis rain gardens were built to reduce water pollution. Research shows theyre making it worse.

A 2021 study suggests that Minneapolis rain gardens, built to mitigate phosphorus pollution, may be exacerbating the issue. City officials have implemented these green infrastructures to manage stormwater and reduce flooding risks, having installed hundreds across various neighborhoods. Although the gardens have shown effectiveness in filtering pollutants like lead, the research highlights a concerning rise in phosphorus levels, with some gardens releasing 2. 7 milligrams per liter, significantly above acceptable limits. The city is now exploring ways to improve the gardens' effectiveness, including reducing compost usage and testing alternative materials that can capture phosphorus.

Toxic algae blooms in local lakes have prompted multiple swimming advisories since 2020, emphasizing the urgency of addressing this issue. Environmentalists still praise rain gardens for their ability to alleviate pressure on storm systems during heavy rains. City officials remain committed to refining the gardens while acknowledging their mixed results. Ongoing research aims to find solutions that better balance the gardens' benefits with their ecological impact.