Dam Passage - CRiSP.1.5 Theory, Calibration & Validation Manual

II.8 - Dam Passage

Fish enter the forebay of a dam from the reservoir and experience predation during delays due to diel and flow related processes. They leave the forebay and pass the dam mainly at night through spill, bypass or turbine routes, or are diverted to barges or trucks for transportation. Once they leave the forebay, each route has an associated mortality and fish returning to the river are exposed to predators in the tailrace before they enter the next reservoir. These regions are illustrated and the details of passage through the regions of the dam are illustrated schematically in (Fig. 47).

Fig. 47 Dam processes showing passage routes and mortality

The movement and allocation of fish through the forebay is illustrated in Fig. 48. Fish entering from the reservoir are delayed in the forebay before they pass through one of three passage routes. Fish exiting the reservoir in each reservoir time slice, typically two slices per day, are evenly allocated as input to the forebay over the dam time slices, which are shorter than the reservoir time slices. In the forebay fish experience mortality. Output from the forebay in each dam time slice depends on flow and diel illumination. Allocation to the passage routes depends on spill schedules and passage efficiencies through the routes. Calculations are performed in the order: mortality, delay, spill passage, dam passage.

Fig. 48 Transfer of fish from reservoir to forebay to dam. Diagram shows allocation of fish from a reservoir time slice of 12 hours to dam time slices of 2 hours each. Four hour dam slices are indicated for graphical clarity.

[Manual] [Contents] [Prev] [Next]

web@cbr.washington.edu