Since the early 1970s, King County’s Cottage Lake has experienced algae blooms due to excessive amounts of phosphorus entering the lake. King County began monitoring the lake and its two inlet streams (Daniels Creek and Cottage Lake Creek) in 1993. As a result of King County’s year-long study, the Cottage Lake Management Plan was created. Data from the lake management plan aided development of the Cottage Lake Water Quality Cleanup Plan (formally known as a Total Maximum Daily Load study) for phosphorus in 2004, followed by the Cottage Lake Water Quality Implementation Plan in 2007.
Elevated levels of total phosphorus in the lake water led to increased occurrences of blue-green algae blooms. Excessive amounts of noxious weeds, such as White Water Lily and Purple Loosestrife, replaced many native plant species in the lake and its wetland areas. Friends of Cottage Lake (FOCL) spearheaded local efforts in the area to provide education and outreach to residents within the watershed through their website. Once the Cottage Lake Implementation Plan was complete, FOCL and King County worked in partnership to develop the Cottage Lake Total Phosphorus Reduction Plan Grant, provided by Ecology’s Centennial Grant Program.
Milestones and outcomes
King County continues to work in partnership with the FOCL to distribute educational materials and to keep residents interested in protecting Cottage Lake and its watershed. Overall, the response from residents living in the watershed has been positive. However, it has yet to be determined if projects conducted in the grant have influenced a reduction in total phosphorus in Cottage Lake and its inlet streams. Further monitoring and analysis of water quality data in the next few years will help to answer these questions.
- Read this full story online.
- Story written by Tricia Shoblom, Ecology Northwest Regional Office
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