Como Lake Alum and Herbicide Treatments

Capitol Region Watershed District (CRWD) is committed to improving water quality in Como Lake, a beloved water resource in Saint Paul for over a century. Despite efforts to address the water quality in the lake over the years, decades of stormwater runoff and pollution have made a new Como Lake plan necessary.

The 70 acre Como Lake drains more than 1,711 acres of land in Saint Paul, Roseville, and Falcon Heights. With a maximum depth of 15.5 feet, it is a shallow body of water. The shallow depth, coupled with significant nutrient and pollution in stormwater runoff, has had a significant impact on Como Lake water quality. In fact, CRWD began when a group of residents raised concerns about the water quality in Como Lake. Accordingly, the District has placed a high priority on improving Como Lake, as it is one of the most recognizable and well-loved water resources.


The Challenge

The biggest challenge facing Como Lake today is too much phosphorus, a pollutant carried to the lake through runoff in storm drains. Over time, high levels of phosphorus-three times higher than Minnesota standards-have led to algae blooms that choke the oxygen from the lake and lead to fish kills. While CRWD and its partners have already worked to reduce phosphorus levels by 20% in the past two decades, water quality in the lake remains poor.

The other main concern in Como Lake is an invasive aquatic plant known as curly-leaf pondweed. The plant is dominating Como Lake’s ecosystem, making it difficult for native plants to survive. Decaying curly-leaf pondweed adds more phosphorous to the water when it dies off, so management is key to achieving CRWD’s water quality goals.

"Capitol Region Watershed District is committed to improving Como Lake. Reducing phosphorus and controlling curly-leaf pondweed are critical for restoring balance." - Britta Belden, CRWD Water Resource Project Manager

The Solution

CRWD, with guidance and support from the City of Saint Paul, Ramsey County and the Minnesota Department of Natural Resources (DNR) have outlined the new Como Lake Water Management Plan implementing the industry’s best practices, science and technology. The Como Lake plan identifies strategies to address the water quality issues, which includes treatment of the water over the course of several years, beginning in the spring of 2020 with herbicide and alum treatments.

View Como Lake Management Plan

Spring 2020 Lake Improvement Projects

Alum Treatment

  • Alum (aluminum sulfate) will be applied to Como Lake this spring to reduce phosphorus being recycled inside of the lake.
  • Alum is commonly used in drinking water treatment and has been a safe lake management tool for decades.
  • The treatment is expected to dramatically reduce algae growth and improve water clarity and quality.

View Alum Treatment Factsheet

Herbicide Treatment

  • An herbicide will be applied to Como Lake this spring to target the overgrowth of an unwanted aquatic plant called curly-leaf pondweed.
  • Many studies have shown that herbicide treatments are the most effective solution for reducing curly-leaf pondweed, and similar treatments have been successfully used on a number of metro area lakes in the past decade.

View Herbicide Factsheet

Como Lake Curly-Leaf Pondweed Video

Frequently Asked Questions