Major Lakes Monitoring Data

King County monitors the ecological health of lakes Union, Washington, and Sammamish in a variety of ways including collecting and analyzing water, plankton, and sediment samples. Data from the Major Lakes Monitoring Program is presented on the pages listed below.

• View a map of lake stations, as well as graphs of conventional, nutrient, and bacteria data for each station. Water quality data can be downloaded from this site.
• Total phosphorus, chlorophyll a, and Secchi depth transparency are used to calculate the Trophic State Index for each lake.
• Algae samples are collected year round at the deep lake stations and seasonally at the swimming beaches to track plankton community structure and potential toxic algae blooms.
• Sediment samples have been collected at various locations around the three major lakes to determine lake sediment quality.
• View reports on the current Status and trends in water quality.