II.5.3 - RESERVOIR Button

Fig. 27 Reservoir menu and submenu

Reach Predator Density: Predator Density in River

Predator densities in each river segment are set in this slider window. Densities are given as number of squawfish per square kilometer of reservoir, excluding the tailrace and forebay. This measure, based on full pool dimensions, is effectively a measure of the total number of predators in a river segment. A segment is defined as a section of river between river elements. It may include dams and confluences.

Dam Predator Density: Predator Density at Dam

Predator densities in the forebay and tailrace at each dam are set with slider tools. Predator numbers are expressed on a square kilometer basis. This function accounts for the increase in predator density at the dam relative to densities in the reservoirs. As forebay and tailrace depths change with pool elevations, the predator density can be specified to adjust according to the change in depth from full pool.

Fig. 28 Predator Density in forebay and tailrace of dam

Predation Probability: Diel Predation Probability

Since predators typically use visual cues to find and capture prey, light levels should effect the rate of predation of fish in the forebay of the dam. Since dam passage varies between day and night CRiSP.1 allows for the probability of predation to change over a 24 hour period in dam time increments (2 hours) (Fig. 29). This is set by sliders that adjust the predation rate to some fraction below the maximum rate. A diel variation in reservoir predation is not applied since CRiSP.1 only uses two time steps over the day.

Fig. 29 Dam Predation Probabilities with time

Water Temp: River Segment Temperature

Water temperature is set on a daily basis in the headwaters. River temperatures in downstream segments are computed according to the fractions of different headwaters in the segment and the temperature of the headwaters on a given day.

River Parameters: River Parameters

These are parameters that are applied throughout the river system and do not depend on species or day.

• pred act exp - predator activity temperature exponent. This adjusts the predation rate to changes in temperature.
• gas dissp exp - an exponent controlling degassing of nitrogen from the water. This depends on river velocity and depth.
• Ufree - velocity in free flowing portions of river.

This tool allows the user to determine the average water particle travel time (WPTT) between any two points in the river system over any time period in the season, for the data conditions that have been read into the model. The panel for this tool is shown below in Fig. 30. Right-click on the arrows to select the upper river segment and lower river segment to define the reach over which you wish travel time to be calculated. Adjust the first and last season day sliders to define the time interval over which you want travel time tracked (default is the entire year, day 1 to day 365). Once you have the settings you want, left-click the "recompute" button to obtain a new estimate. Unpin the window or left-click the Done button to dismiss the window.

Fig. 30 Water Travel Time tool window