Projects & Programs
Three-Dimensional Hydrodynamic Modeling of Circulation in Lake Billy Chinook, Washington
A three-dimensional (3-D) hydrodynamic model was used in conjunction with a hydrothermal mass balance model to simulate the density driven circulation in Lake Billy Chinook. Lake Billy Chinook reservoir, created by the construction of Round Butte Dam, receives flow from three tributaries (Crooked, Deschutes and Metolius) that have distinct temperature and flow characteristics. The velocity pattern in the lake is dominated by temperature stratification and is also affected by wind stresses. The existing flow conditions are considered to be ineffective for collection and passage of downstream migrating fish. The immediate goal of the project is to identify the modification(s) most favorable to the downstream passage of juvenile salmon through the project.
The calibrated hydrodynamic model reproduced the flow patterns well and showed that flows in the reservoir were the result of a combination of density-driven circulation, wind and river inflows.
The model was used to evaluate the effectiveness of various proposed flow modification structures on reservoir stratification and circulation. The hydrodynamic model was externally coupled to a temperature model. This study demonstrated the effectiveness of these models in identifying the forcing mechanisms for the lake circulation patterns and aiding the design of fish passage facilities.
Project Highlights:
- The model was calibrated successfully and reproduced observed current circulation patterns in the lake
- The model served as a tool to evaluate effectiveness of various alternatives for modifying flow patterns to enhance downstream passage
- The modeling-based study confirmed that complex currents at the collection point were the potential cause for failed passage
- The study facilitated selection of an optimum alternative
- The selective withdrawal alternative effectively modified currents to enhance fish collection downstream passage.