The King County Water and Land Resources Division operates near-continual water quality profiling platforms on Lake Sammamish and Lake Washington. A multi-parameter sonde collects near-real-time water quality data at programmed depth increments and time intervals. The parameters measured by the profiling equipment at each location include depth, temperature, dissolved oxygen, pH, specific conductance, turbidity, chlorophyll fluorescence, and blue-green algae fluorescence. In addition to water column profiling data, the platforms are equipped with weather stations that collect near-real time data at programmed time intervals. The weather data collected include air temperature, relative humidity, wind speed, wind direction, atmospheric pressure, and solar radiation.

The objectives of the program are (1) collect near-continuous (every 4 to 8 hours depending on the season) depth dependent measurements of selected field parameters at central locations on Lake Washington and Lake Sammamish, (2) assess temporal trends in water quality parameters measured at each location, and (3) report near real-time water quality and weather data through a public King County web site.

This Quality Assurance Project Plan (QAPP) is based on established field and laboratory procedures and U.S. Geological Survey (USGS) standards for continuous water quality monitoring. A QAPP prepared by the USGS for water quality profiling on Lake Mead was also used as guidance. This document presents the overall QAPP for operation and maintenance of the system (i.e., profiling platform, SQL database, and publicly facing website) and the methods used to assess the quality of the data collected.