II.11.2 - Stochastic Parameters

Variability in the predator activity coefficient used in eq (64) has deterministic and stochastic parts. The equation is

(165)

where

• a₀ = deterministic part set by sliders for each species where value of the activity is set by the mean value slider
• a'₀ = stochastic part whose range for a given species is set by the low and high value sliders.

Supersaturation Mortality

Variability in nitrogen supersaturation mortality is incorporated by giving the gas mortality coefficient used in eq (103) deterministic and stochastic parts. The equation is

(166)

where

• a = gas mortality coefficient deterministic part and is set by mean value sliders for each species
• a' = stochastic part whose range for a given species is set by the low and high value sliders.

Migration

Variability in the migration rate is determined by the equation

(167)

where

• r(t) = determined from eq(52)
• V(i) = variance factor which is different for each release i.

The variance factor assumes that variability in migration velocity relative to water velocity is associated with a particular stock of fish. Studies of travel time support this assumption since particular stocks exhibit their own unique relationship with flow.

Flow

Flow Variability is represented on a daily basis when running in the Monte Carlo mode. In this case, daily flow variation is expressed by an Ornstein-Uhlenbeck process. Details of this are described in the Spectral Analysis of Flow section II.3.2.

In the Scenario Mode, daily flow variations are described by a random process in headwater flow. Details of this process are described in the Headwater Modulation section II.3.3.

Dam Passage

Variability in dam passage parameters is applied on each dam time slice, (typically 2 hours). The variability is generated from the broken-stick distribution and is applied to the following variables:

• bypass mortality
• spill mortality
• turbine mortality
• transportation mortality
• day / night fge
• spill efficiency.