The Role of Physical and Numerical Modeling in Design Development of the Priest Rapids Fish Bypass

Abstract

This paper describes a number of years of physical and numerical modelling that were instrumental in the development of the final fish bypass design at Priest Rapids Dam. Three physical models and multiple numerical models were used to guide the design of the fish bypass including its location on the dam, impact on forebay and tailrace flow patterns, intake configuration, design flow rates, flow control scheme, tailrace egress, potential for scour near the dam, potential impacts on total dissolved gas (TDG), impacts on spillway and powerhouse operation, and overall fish friendliness of the bypass. Throughout those years of design work, results from actively tagged salmonid smolt studies were used to guide and validate each step of the design process. In 2011, a construction contract was awarded, and the Priest Rapids Fish Bypass facility was completed in the early spring of 2014. Final validation of this newly constructed facility came in the spring of 2014 with a survival and behavior study conducted using acoustic tagged yearling Chinook and juvenile steelhead smolts to evaluate the salmonid smolt survival rate through the bypass along with the fish passage efficiency (FPE) of the bypass facility. This paper discusses the physical models plus CFD models used to support the design development of a non-turbine fish bypass and presents the results of the survival and behaviour studies conducted after the fish bypass was installed at Priest Rapids Dam.