Thesis (M.S.)--Portland State University, 1993. / Computer-produced typeface. Includes bibliographical references (leaves [111]-114). Also available on the World Wide Web.

Increased population growth in Washington County, Oregon, has helped cause the water quality of the Tualatin River to decline. Henry Hagg Lake is a storage reservoir which was built to augment summer low flows in the Tualatin River. Hagg Lake also supplies the Tualatin River Basin with both irrigation and municipal water in the summer. Using the U.S. Army Corps of Engineer's model CE-QUAL-W2 (a two-dimensional hydrodynamic and water quality model) , a model of Henry Hagg Lake was created. The model was calibrated using water quality and hydraulic data for 1990 at the Hagg Lake outflow in Scoggins Creek. A verification simulation was performed with similar field data for 1991. The model was used to evaluate the water quality of Henry Hagg Lake if more flow were allowed out of the reservoir than current allocations permit. This model simulation showed that the water quality of Hagg Lake would not be severely affected, however, recreation in the lake would be. Additional particle sizes for inorganic suspended solids introduced to the lake by streamflow were added to the model. The model was used to track suspended solids in Hagg Lake through a summer season. Field data for the modeling of Hagg Lake were very limited. Thus, firm conclusions about the validity of the model would require further field data.

From June 1998 to July 1999, the dynamics of the plankton in Hagg Lake and Barney Reservoir were studied with the purpose to identify the succession dynamics of the planktonic species, to test the Plankton Ecology Group (PEG) model, and to explore the relationships between these successions and the physical and chemical variables.