Abstract:
Water quality problems related to excessive algal
growth, high nutrient loading, and low flows have been
occurring along Oregon's Tualatin River. The Tualatin River
is 86 miles long and has a drainage basin of 711 square
miles. The drainage basin incorporates forest,
agricultural, and urban areas. Located in the Portland
metropolitan area, these problems have been acerbated by the
effects of urban growth. To help analyze pollution control
alternatives, a river model study, funded by the Oregon
Department of Environmental Quality (DEQ), was undertaken.
An in-stream model of hydraulics and water quality was
developed. The Corps of Engineer's CE-QUAL-W2 model, a twodimensional,
laterally averaged, dynamic model of
hydrodynamics and water quality was applied to the Tualatin
system. Calibration of the main pool model of the Tualatin
River was from field data taken during June through August
of 1991. Verification of the model was performed from field
data taken during the summer of 1990. After calibration and
verification of the model, management alternatives were
evaluated in order to achieve DEQ mandated water quality
standards. Environmental performance criteria were
determined to evaluate differences between model scenarios.
Management alternatives focused on the reduction of point
and non-point sources of pollution, flow augmentation, and
structural changes in the river system, such as removal of
the Lake Oswego Diversion Dam.
