Conditional-yield operating rules for low-flow management

A family of reservoir operating rules, termed conditional-yield operating rules, is developed for operation of water quality storage in a multipurpose reservoir. Conditional-yield rules generalize safe-yield rules in a straightforward fashion. An important feature of conditional-yield rules is that they can be represented as parametric operating rules, that is, operating rules for which release is specified as a function of previous inflow and a vector of operating parameters. Conditional-yield rules have a natural relationship with a maximum-yield problem. Solution of the maximum-yield problem specifies not only yield of the system but also operating parameters required for implementing the rules. A key feature of the statistical framework proposed for development of reservoir operating rules is that the random component of the problem, reservoir inflow, is treated in a non-parametric framework. Procedures are applied to water quality operation of Jennings Randolph reservoir, a multipurpose reservoir located in the headwaters of the Potomac River basin. It is shown that large increases in the average yield from water quality storage can be achieved, relative to safe-yield rules, with only a modest increase in the risk of not meeting a minimum-flow threshold.