Remember, each rule you create describes a desired limit on the allowable range of release from the reservoir. Although some rules are inherently a specific limit type, the release function rule, with all its flexibility requires that you select the limit type as part of the rule definition.

Select that the Limit Type from the selection list ("Figure: Rule Limit Type"). Your options are:

Figure: Rule Limit Type

  • Minimum
  • Maximum
  • Specified

Specify the limit type early in the process of defining your rule because it keeps your mind focused on your objective while you complete the rest of the rule definition.

NOTE: Use the specified limit type with caution.

Most operational constraints describe either a minimum or maximum release limit. Specified rules describe the precise amount of flow to be released, neither more nor less, making them effectively both a minimum and a maximum limit at the same time. As such, a specified release rule is very restrictive because it sets the allowable range of the release to a single value. If specified is the appropriate limit type, consider carefully where to place the rule in the rule stack. Unless the rule applies to a specific outlet, the bottom of the rule stack is usually the best place for specified-limit rules; in this position, other rules have a chance to influence the allowable range.