DEATH TO RULE CURVES

The purpose of this paper is to focus attention on the potential for increasing the benefits from existing dams. Some reservoirs are operated by controlling releases to maintain reservoir water levels within established bounds that depend on the time of year. These time dependant bounds, or "rule curves", are determined by office studies that may have evolved many years ago during the design of the dam. Rule curves have one advantage - simplicity for the operator of the dam. They can have two disadvantages - disregard for present circumstances of weather and watershed conditions, and lack of a clearly defined objective function. In general, rule curves displace opportunities for optimization with a blind constraint. In specific cases, rule curves can be arrogant artifacts that restrict discretion, wisdom, experience, and effective use of real-time data. The alternative is to provide operators of river systems with decision support systems that recommend current reservoir releases based on currently observed data and computer models that will satisfy constraints and maximize an objective function. This paper describes how such models are developed and two of the applications where they have been implemented.