The Peak Arrival & Run Size predictions for spring Chinook at Bonneville Dam begin with a preseason prediction of run timing from a Genetics and Environment Timing model¹ and a preseason run-size prediction. The daily, inseason methods to simultaneously estimate distribution parameters from the observations-to-date include use of up-to-date environmental conditions, historical bounds on parameters, and the mathematical properties of the gaussian distribution. The complete run of Chinook in the Columbia River is the sum of three sub-runs—spring, summer and fall—each well characterized by a gaussian distribution.

1. Anderson and Beer. 2009. Oceanic, riverine, and genetic influences on spring Chinook salmon migration timing. Ecological Applications. 19(8):1989-2003.