Reservoir operation is the act or process of storing water in and releasing water from a reservoir. The operations for most reservoirs regulated by the U.S. Army Corps of Engineers are based on a concept called Guide Curve Operation.
Guide Curve Operation is the process of determining and making releases from a reservoir in order to get to and maintain the reservoir pool at its target elevation. Thus, the guide curve is the target or desired pool elevation for the reservoir.
Reservoir operating zones are another concept related to the guide curve. An operating zone is a horizontal slice of the reservoir pool for which the goals and constraints differ from those in another zone of the reservoir.
The operating plan for most reservoirs is described in a reservoir regulation or water control manual. The water control manual for most Corps of Engineers reservoirs describes a seasonally-varying target pool elevation commonly called the Guide Curve. The (available) storage of the reservoir above this target elevation is referred to as the Flood Control pool and the storage below the guide curve is called the Conservation pool. The guidelines for determining the release from the reservoir are then based on where the current pool elevation is in relation to the guide curve. With guide curve operation as the fundamental objective of the reservoir operation, all other goals and objectives described in the regulation plan or water control manual can be interpreted as limits on guide curve operation.
Since ResSim was designed for modeling Corps reservoirs, the foundation of the ResSim decision logic is basic Guide Curve Operation. This means that, to ResSim, the primary reservoir operating objective is to maintain the pool at, or return the pool to, the guide curve elevation as soon as possible. So, if the pool is below the guide curve, guide curve operation would reduce or suspend releases in order to refill the pool; if the pool is above the guide curve, then releases would be increased up to maximum capacity in order to draw the pool back down to the guide curve elevation.
Operational rules that reflect the goals and constraints on the reservoir operation act as limits on the guide curve operation. A well-designed set of rules will temper the potentially volatile release behavior of the guide curve operation and produce smooth transitions across reservoir operating zones without abrupt or oscillating changes in the releases.
In a manner similar to the methods a regulator may use, each reservoir in your ResSim network must determine how much water to release at each timestep of a simulation run. In ResSim, reservoir operation is the timestep by timestep simulation of the release decision-making process over a time window.
This chapter will describe the Operations Tab of the Reservoir Editor and guide you through the process of creating and managing your reservoirs' operating plans (Operation Sets), defining the operating zones in each plan, and specifying the allocation of the release to your outlets. Creating and managing the operating rules that you will add to the zones in your operation sets will be covered in "Reservoir Operations - The Rules". "Advanced Features" covers creating and managing IF-Blocks, State Variables, and Scripted Rules ("IF_Blocks", "State Variable", and "Scripted Rules", respectively), as well as some advanced operation features that can be applied to the operation set ("Capacity Outage Schedules", "Storage Credit", "Reservoir Decision Schedule", "Projected Elevation").