Three-dimensional Modeling of Temperature Stratification and Density-driven Circulation in Lake Billy Chinook, Oregon

摘要

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, Oregon. 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 ineffective for collection and passage of downstream migrating fish. The immediate goal of the project is to identify the reservoir geometry modification(s) most favorable to the downstream passage of juvenile salmon through the project. In this paper, we present application of a 3-D hydrodynamic model to evaluate the effectiveness of various proposed flow modification structures on reservoir stratification and circulation. The hydrodynamic model is externally coupled to a long-term seasonal temperature model to provide temperature initial conditions for the hydrodynamic model. This study demonstrated the effectiveness of these models in identifying the forcing mechanisms for the lake circulation patterns and assisting the design of fish passage facilities.