Lake of the Woods is a large freshwater lake that spans parts of Ontario, Manitoba and Minnesota.
Lake of the Woods and the streams and rivers that flow into it are used for drinking water, electricity, recreation, agriculture and fisheries in Ontario, Manitoba and Minnesota.
High phosphorus levels are one of the key agents causing extensive growth of blue-green algae (or "pond scum"), which can be toxic. Wide swaths of algae impair water quality for recreation, drinking water and lake trout habitat.
Phosphorus is a naturally occurring nutrient that all living things need to thrive. However, too much phosphorus contributes to an unhealthy ecosystem. When phosphorus enters waterways, it acts as a fertilizer, leading to the overgrowth of algae, which can deplete the water's oxygen supply and diminish aquatic habitat. Large quantities of algae can be unsightly and affect the taste and odour of drinking water.
Phosphorus is a natural substance found in rocks and soil, and is a key nutrient in fertilizer. The trouble is, too much phosphorus is entering Lake of the Woods from both natural and everyday human activities such as atmospheric deposition, wetlands, gardening and lawn care, farming, boating, septic systems, and the use and disposal of products that contain phosphorus in our homes. Too much phosphorus means too much harmful blue-green algae.
We invite you to explore the rest of this web section to learn what Ontario is doing to protect Lake of the Woods and the progress we've made. Residents near Lake of the Woods can also learn many ways they can reduce the amount of phosphorus entering the lake by making some simple changes.