06/03/2026
There have been concerns about the state of water quality on the western bays, including Harrisons, West Arm and Jennings. These concerns were brought to the watershed for comment and below is some helpful information.
Comments from Minnehaha Creek Watershed:
“West Arm Water Quality Conditions
As you know, West Arm, and therefore Jennings and Harrison’s Bays are impaired for excess nutrients, which are a key driver of algal blooms. As such, West Arm routinely fails to meet state water quality standards for monitored annual phosphorus concentrations, Chlorophyll-A, and Secchi depths (water clarity). MCWD's most recent monitoring data for Jennings Bay from 2024 and 2025 showed both Total Phosphorus and Chlorophyll-A concentrations within the observed range of conditions documented over the past two decades.
Even with these long-term trends, like most lakes, water quality in West Arm can vary considerably from season to season and week to week. This time of year, Spring lake turnover, large runoff events, and periods of warm sunny weather can all contribute to elevated algal growth. Last week’s storm event, which dropped over 1.5 inches of rain across much of the Twin Cities, generated substantial landscape runoff to West Arm and delivered additional nutrients from the watershed. Combined with the recent warm weather, those conditions are likely contributing to the green water and reduced clarity reflected in the Facebook photos. While frustrating, these types of blooms are not unusual in nutrient-impaired lakes and are consistent with spring runoff driven patterns observed through MCWD's long-term monitoring program.
Algal Blooms
We are currently seeing similar blooms across much of the region’s lakes, both within and outside of the Minnehaha Creek Watershed. Not all algal blooms are harmful to human or pet health. However, when residents are uncertain about algal bloom conditions, the safest approach is to avoid contact. The Minnesota Pollution Control Agency provides guidance on identifying and avoiding the impacts of harmful algal blooms on their website.
Long-Term Water Quality Improvements to West Arm
Since nutrients from the watershed remain a primary driver of water quality conditions, MCWD’s strategy for long-term improvement in Jennings and Harrison’s Bay is focused on reducing external nutrient loads coming from the Painter Creek Subwatershed. As you know, MCWD has been monitoring the system over the past year and a half, to pinpoint sources, drivers, and identify potential project opportunities.”
