Development of Two-Dimensional Hydraulic Models to Predict Distribution of Manayunkia speciosa in the Klamath River

 We developed two-dimensional hydraulic models at three study sites in the Klamath River. This report describes the data collection, calibration, and validation performed to build the models and test their performance. The hydraulic models showed excellent agreement between predicted and observed water surface elevations, area of inundation, and spatial distributions of depth and velocity both at calibration and independent validation discharges. Water surface elevations were predicted within an average of 0.048 m at calibration streamflows and 0.076 m at validation streamflows. Water inundation extent was predicted within an average of 0.39 m at calibration streamflows and 0.31 m at validation streamflows. The predicted depth and velocity patterns generally matched observed data, with 90% of predicted depths within 0.15 m of observed values and 90% of predicted velocities within 0.45 m/s of observed values. Fine-scale velocity, depth, and shear stress predictions computed by the hydraulic models will be used to develop habitat preference models for Manayunkia speciosa, the freshwater polychaete that is an intermediate host for the salmonid parasite Ceratomyxa shasta. This information will allow scientists to evaluate whether flow manipulation is a potentially viable management action to impair hydraulic habitat and disrupt the disease cycle.