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What is a scenario?
Basis of comparison
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- Compares a baseline with an alternative
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- Compares two alternatives
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Involves modification of operating rules
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Notes:
Scenarios are commonly (but not always) driven by an alteration of the hydrologic regime. The baseline flow regime is usually defined by the empirical flow record for recent history, e.g., the past 20 to 50 years. Sometimes, the baseline is simulated via a hydrologic model, using past operating rules for reservoir operations and water allocations along with historic inflow data. For restoration applications, the baseline may be defined as a reconstructed flow regime to represent pre-development hydrology.
Alternatives are generated by imposing different operating rules on the system, whether modifications to the rule curves for reservoir operations and/or modifying water allocations among uses. In some cases, the alternative can involve structural modification, such as altering the channel to create specific habitat types or increasing vegetative shading to moderate water temperatures.