Use of Acoustic Backscatter and Vertical Velocity to Estimate Concentration and Dynamics of Suspended Solids in Upper Klamath Lake, South-Central Oregon: Implications of Aphanizomenon flos-aquae

摘要

Upper Klamath Lake, the largest freshwater lake in the State, is located east of the Cascade Range in south-central Oregon. The lake has been historically eutrophic (Eilers and others, 2004) and has experienced annual occurrences of large cyanobacterial blooms (primarily Aphanizomenon flos.aquae, or AFA) in recent decades. Growth and decomposition of dense AFA blooms frequently cause extreme water quality conditions characterized by high pH (9.10.2) and ammonia concentrations (> 0.5 mg/L unionized) and widely variable dissolved oxygen (anoxic to supersaturated) (Wood and others, 2006; Hoilman and others, 2008). These conditions are detrimental to the survival of two endangered fish species endemic to the lake, the Lost River and shortnose suckers. In order to complement water quality samples with better spatial and temporal resolution, it may be possible to use measured acoustic backscatter as a surrogate for suspended solids. In addition, if properly calibrated, acoustic Doppler current profilers (ADCPs) can provide non-intrusive measurements to compute time series of suspended solids concentration (SSC) profiles concurrent with measurements of three-dimensional velocity profiles (Gray and Gartner, 2009).