Multi-Criteria Model for Redbluff
In the past decade much attention has been paid to multi-criteria evaluation approaches to determine management alternatives for complex public resource systems. As decision making tasks increase, researchers have observed systematic discrepancies between rational theory and actual behavior. In other words, given the choice between management alternatives people will not consistently select the "best" alternative based on evaluation criteria. Evidence exists suggesting that even experts in public resource management have great difficulty in intuitively combining information in appropriate ways. Because of the severe limitation on the intuitive decision making process, analytical methods can be used to help determine the worth of multi-attributed alternatives. One technique that has been used successfully is multi-criteria analysis. This method can rank existing alternatives quantitatively according to weighted criteria.
The Multi-Criteria Model has been developed as a response to ineffective fish passage capability at the Red Bluff Diversion Dam (RBDD), located in north central California. This problem has been identified as a contributing factor in the decline in the populations of anadromous fish in the upper Sacramento River. The most significant decline has been experienced by the winter-run chinook salmon, now protected under Federal and State Endangered Species acts. The purpose and need of the Red Bluff Fish Passage Program (RBFP Program) is to improve fish passage capability at RBDD for salmon migrating upstream and downstream on the river. The Multi-Criteria model has been developed for the (RBDD) project, a coordinated effort between the Bureau of Reclamation, U.S. Fish and Wildlife Service (FWS), National Marine Fisheries Service (NMFS), and California Department of Fish and Game (DFG). The model's objective has been to find the optimal alternatives within the conflict criteria specified by the Bureau of Reclamation related to the RBDD.
The model consists of three components: Define Alternatives, Compare Alternatives, and Multi-Criteria Analysis (MCE). The model has been designed in C++ to run on a personal computer under Microsoft windows and was built in a modular and generic fashion to allow for its future application to other environmental or water resource problems. The Define Alternatives component provides the decision maker with the ability to create a new alternative with a set of options. The Compare Alternatives component allows the user to compare as many as four alternatives simultaneously according to biological and economic criteria. The MCE component allows the weights of each criteria and sub-criteria to be changed as the decision maker requires, with all alternatives being evaluated.
In the Multi-Criteria Model developed for the RBDD, several options can be defined when creating a new alternative.
Ladders & Bypass indicate the three positions where fish ladders can be constructed or already exist on the diversion dam (left, center, and right). The left fish ladders are along the north bank of the Sacramento River and the right ladders are along the south bank. Currently, there are fish ladders on both the left and the right bank of the river. Some alternatives propose enlarging these ladders and possibly installing a center ladder. A bypass would be an alternate route for salmon past the dam. Currently no bypass exists, but some proposals suggest installing one.
Controls are of three types: Public Opinion, Biological, and Economic Factors. Biological and Public Opinion controls will be displayed within the Define New Alternatives Screen (Figures 1 & 2) and the Economic Factors control is shown in Figure 3.
Line graphs are primarily used for setting the gate schedule. In Figure 1, the upper graph refers to total water inflow, while the lower graph refers to the amount of water obligated to agricultural users. Selecting one of the boxes under the graphs closes the dam for a two week period (two boxes represent one month).
Total Salmon Passage is the amount of salmon fry that successfully make it past the Red Bluff Diversion Dam.
Total Salmon Mortality is a summation of all the mortality rates for salmon fry migrating to the ocean and salmon runs back up the river to spawn.
Current Scenario reflects an alternative which is selected; the data for that particular alternative will be reflected along the right side of the window under the current alternative scroll list. The user can modify this alternative and save with the File Save option.
Five factors are listed along the right side of the Define New Scenarios screen:
- Total Projected Cost
- Benefit/Cost Ratio
- Cost Effectiveness
- Power Cost
- Total Salmon Passage
The Economic Factors shown in Figure 3 include Cost Factors, Economic Factors, and Fisheries Data.
Cost Factors include such data as annual equivalent cost, the period of construction; as well as the operations, maintenance, and repair costs that can be expected over the life of the system and the power costs that can be expected for the pumps when the gates are closed.
Economic factors include the interest rate that can be expected on the loan for construction costs, trips per salmon for river sport and ocean sport fishing, value per trip for river and ocean sport fishing, and price per pound of salmon.
Fisheries data includes the salmon base population for fall, spring, winter, and late fall; river carrying capacity for fall, spring, winter, and late fall; and catch- escapement rations for winter and non- winter (rates are for commercial, river, and ocean sport fishing).
After Defining Alternatives, the user will want to evaluate these alternatives using the Multi-Criteria Evaluation. In the Multi-Criteria Evaluation, three different criteria are observed: Effectiveness, Efficiency, and Acceptability. Depending upon the user's preferences, these criteria can be ranked and judged accordingly.
Each of the criteria reflect a different aspect of the decision-making process. Effectiveness shows how well the salmon mortality problem is solved by the alternative, efficiency describes how cost- effective the chosen alternative is, and acceptability is related to the public and political reception of the alternative and shows how well the alternative complies with existing regulations.
The graphical representation of these criteria is displayed in Figure 4. The screen contains three components: Graphs, Alternatives, and Change Weights.
Graphs in the Multi-criteria Evaluation at the intermediate user level represent how the various alternatives are ranked. The different bar shades represent the three criteria. At the basic user level, only the first graph is displayed and at the technical level the criteria and the sub- criteria are displayed.
Four different alternatives can be selected for comparison. Selecting the arrow on the right hand side of the alternative title box will display a scrollable list with different alternatives. This scrollable list orders the ranked alternatives in relation to the user defined criteria. The best ranked alternative is displayed first.
As the user compares different alternatives, the different criteria and sub- criteria which comprise the analysis can be changed by accessing the Change Weights function.
By choosing the Change Weights function, the main criteria by which an alternative is evaluated can be adjusted (Figure 5). In addition, each criteria can by modified by weighting the sub-criteria. For example, while effectiveness shows how well the salmon mortality problem is solved by a specific alternative, effectiveness is determined by subcriteria such as percentages of adult salmon saved overall as well as the percentage of adult salmon saved in the winter run. By choosing the Set Subcriteria function, components of each criteria may be set.
The Multi-Criteria Evaluation allows the user to compare the alternatives by a ranking system. When a more detailed analysis of the alternatives is desired, the user may choose to compare alternatives. By choosing this function, four alternatives may be compared by their individual components (subcriteria). In this manner, different aspects can be numerically modelled such as Benefit/ Cost Ratio, Average Net Benefits, Total Fish Survival, Fall Fish Survival, and Spring Fish Survival. For some users, these individual components may contain useful data to accompany the Multi- Criteria Evaluation.
The Weighted Average Method is probably the most commonly employed comparative evaluation procedure. Essentially, numerical values are obtained for each alternative to reflect each criteria and weights are assigned to each criterion. The most important step in multi-criteria evaluation methods is the assignment of weights. Weights reflect the relative importance of the various impacts considered. To obtain weights, the decision maker is asked to distribute a constant number of points among the criteria so that the number of points allocated to an criteria reflects its relative importance.