CRiSP1.6 Theory & Calibration Manual: II.1 - Model Computation Diagram

II.1 - Model Computation Diagram

CRiSP.1 is a composite of individual integrated process submodels that jointly determine smolt migration and survival. The equations underlying some submodels are mechanistic and are derived from underlying theory. In these equations, the parameters have ecological or physical meaning. For example, the equation relating water flow to velocity is based on principles of hydrology. A second type of equation is empirical and has no underlying ecological or physical meaning. These equations are used because they fit the data and are amenable to statistical fitting techniques. The parameters of the empirical equations seldom have ecological interpretations. For example, in the total dissolved gas (TDG) supersaturation submodel four alternative equations are available to relate TDG supersaturation to spill. Here, the parameters just determine the shape of the response. A third type of equation is a mixture of empirical and mechanistic. The predation rate equation (submodel) is an example of this mix with predation activity and density parameters multiplying the empirical predation temperature response.

The CRiSP.1 model calculates changes in fish population numbers as fish move through tributaries, reservoirs, and dams. Figure 3 is a diagram of the computational tree. Shaded boxes represent fish entering the system of dams and reservoirs on a daily basis. Unshaded square boxes represent calculations for travel time and survival of fish through the system. Rounded boxes represent input data to the calculation modules.

Fig. 3 Diagram of model elements

Reservoir Passage

In CRiSP.1, passage and survival of fish through a reservoir is expressed in terms of the fish travel time through the reservoir, the predation rate in the reservoir and a mortality rate resulting from fish exposure to total dissolved gas supersaturation, an effect called gas bubble disease (GBD). CRiSP.1 combines these individual mortality factor models (Fig. 4).

Fig. 4 Reservoir mortality processes

The modeling approach has been to develop alternative submodels of reservoir mortality factors so that various hypotheses can be evaluated and compared.

Ecological Submodels

Ecological submodels were developed from first principles relating environmental variables with fish behavioral and physiological factors to determine fish passage. Environmental variables-including weather-related factors such as temperature, and system operating factors such as flow, spill and fish transportation-describe the observable state of the environment in which fish live and characterize the rates of fish passage and survival which, through the model equations, generate predicted passage. In the model, these variables are contained in the Reservoir, Behavior, Flow, and Dam menus.

The model can use both raw information and statistically analyzed data. The model runs on data expressed as initial release numbers and numbers of fish passing any point or bypass route in the river system. Release information is accessed through the Release menu. The Passage menu provides access to passage histograms for each reach and dam in the model and for each of the four dam passage methods: bypass, turbine, spillway, and transport. The model run output provides detailed information on passage at any level from passage of a specific dam route to passage through the entire system.

CRiSP1.6 Theory & Calibration Manual: II.1 - Model Computation Diagram