Vancouver Lake, located in Clark County, near Vancouver, Washington, is a relatively large (approximately 2,300 acres) and shallow (mean depth 3–5 ft) lake that has recreational, environmental, and aesthetic value to the local community. It is the largest lake of the historical Columbia River floodplain lakes, and it is the largest lake in the Portland/Vancouver metropolitan area. In the late 1800s, the lake was much deeper (20 ft in some places) with clear waters (Bhagat and Orsborn, 1971).
Historically, the lake was connected to the Columbia River and degradation of water quality began shortly after flood control structures for the Columbia River were constructed, which severed the connection to ‘flushing’ water. Nutrient and sediment loading has increased over time, and hypoxia (low dissolved oxygen concentrations) and cyanobacterial blooms in the lake led to poor water quality as early as the 1960s.
The first detailed water-quality study of the lake took place in 1967–68 by scientists at Washington State University (Bhagat and Orsborn, 1971). This early work was undertaken to assess how water quality would change if the hydrological characteristics of the lake were altered by the addition of a ‘flushing channel’ that would reconnect the lake directly to the Columbia River. The hope was that restoring this connection would decrease residence times in the lake and promote better flushing that would address water-quality issues. In the early 1980s, the flushing channel was completed.