Lake Water Quality

This project compared phosphorus, E. coli, and standard water quality parameters of two major inlets, Sucker and Hemlock creeks, to determine their impacts on Silver Lake. Additionally, lake sediment was evaluated for contaminants of concern. Below is a summary of the results over the course of the study. The summary of results is also available in the Final Report – Silver Lake.

• Phosphorus: Over the course of the study, the lake averaged 0.058 mg/L total phosphorus, while streams averaged 0.037 mg/L.
• E. coli: Levels were significantly higher in the streams than in Silver Lake and varied seasonally.
• Secchi: These values varied seasonally as we have seen in past studies.
• Dissolved Oxygen: The streams had clear seasonal trends with higher levels in the winter than in the summer. Silver Lake had similar trends but with more variability across the lake. 
• Temperature: Stream temperatures were slightly lower than the Silver Lake average but mirrored the annual pattern.
• pH: Stream pH more consistently hovered around 7.4, while the lake pH was slightly higher than 7.5.
• Sediment: Results fell below the recommended standard as outlined in the Dredge Material Management Program.

Digitization: This project also included digitization of the Silver Lake Watershed Management Plan, making it more accessible to the public. The original document was written in 1994 by the Cowlitz County Conservation District and included Darin B. Houpt, Forest Hydrologist, and Resource Technicians Joanne Aylesworth and Steve Stinson.The digitized plan is available by using the following links:

• Silver Lake Watershed Management Plan Summary
• Silver Lake Watershed Management Plan pt. 1
• Silver Lake Watershed Management Plan pt. 2

Other documentation: 
Quantifying Development in the Silver Lake Watershed