Summary

Description

The Comprehensive Passage (COMPASS) model was developed by the Northwest Fisheries Science Center (NWFSC) in collaboration with scientists from other federal agencies, state and tribal agencies, and the University of Washington. The model predicts the effects of alternative dam and reservoir operations on salmon survival rates, expressed both within the hydropower system and through adult return. The model was designed to accommodate a range of alternative hypotheses regarding the functional form of underlying relationships. COMPASS moves cohorts of fish through the hydrosystem according to behavioral rules. A hydrological model simulates flows and temperatures, and dam operations are specified. Fish move through reservoirs based on specified migration rates and rates of spread, and suffer mortality according to relationships that relate survival to travel time, travel distance, flow, magnitude of spill, and temperature. Fish can pass dams through several alternative passage routes, including turbines, spillways, and juvenile bypass systems, and each route has a probability of passage and survival. Fish that pass through bypass systems at the three uppermost dams on the Snake River can be placed into barges for transportation to below Bonneville Dam. For Biological Opinion (BiOp) modeling, we used a relationship that related adult return rate to timing of arrival below Bonneville Dam. Database of output produced by the COMPASS model