Chapter 11 - Reservoir Operation

CONFLICTS IN RESERVOIR OPERATION

While operating a reservoir that serves more than one purpose, a number of conflicts arise among demands for various purposes. The conflicts that arise while operating a multipurpose reservoir may be classified as follows:

• a)

  Conflicts in Reservoir Space

  These conflicts occur when a reservoir (of limited storage) is required to satisfy divergent purposes, for example, water conservation and flood control. If the geological and topographic features of the dam site and the funds available for the

CRITICAL ISSUES IN RESERVOIR OPERATION

According to James and Lee (1971), the following six issues need to be optimally resolved while developing an operation policy of a reservoir:

• 1.

  Use of Flood Storage: Whether flood inflows should be stored to reduce current damages or released to provide additional storage space in case new rains produce even greater flows.

• 2.

  Use of Total Storage: Whether storage space should be filled to save water for beneficial use or emptied to contain potential floods.

• 3.

  Release of Stored Water: Whether water

BASIC CONCEPTS OF RESERVOIR OPERATION

The drawdown refill cycle of a reservoir is usually 12 months long except when the reservoir capacity is large in relation to streamflows. The cycle may extend over many years in arid regions. In many regions of the world, the refill periods (when inflows are more than the demands and therefore extra water is stored in the reservoir for later use) and drawdown periods (when inflows are smaller than the demands and therefore water is withdrawn from storage to meet various demands) are distinctly

RULE CURVES

A rule curve or rule level specifies the desired storage to be maintained in a reservoir as closely as possible during different times of the year while trying to meet various demands. The rule curves are generally derived by operation studies using historic or generated flows. Here the implicit assumption is that a reservoir can best satisfy its purposes if the storage levels specified by the rale curve are maintained in the reservoir at different times. The rule curve as such does not give

OPERATION OF A MULTI-RESERVOIR SYSTEM

The discussion so far was limited to operation procedures for a single reservoir. It is well known that the benefits from the joint operation of a system of reservoirs can be substantially larger than the sum of benefits obtained from the operation of individual reservoirs. A system may consist of reservoirs in series, in parallel, or a combination. Approaches to develop operation policies for a system of reservoirs are discussed in the following. Some of these operational policies are

RESERVOIR OPERATION FOR FLOOD CONTROL

Among the measures of flood control, a storage reservoir with gates to control the outflow is perhaps the most effective means. The moderation of a flood through storage is achieved by storing a part of flood volume in the rising phase of the hydrograph and releasing the same gradually in the receding phase of the flood. The degree of moderation or flood attenuation depends on the empty storage space available in the reservoir when the flood impinges on it. The flood control pool must be

SYSTEM ENGINEERING FOR RESERVOIR MANAGEMENT

Determination of the reservoir operation policy to efficiently manage available water is a complex problem because it involves random hydrologic events. Many attempts have been made to solve this problem using optimization and simulation models. Reservoir optimization models allow the user to generate operating decisions that are optimal in some “measurable” sense. By making a number of runs of a simulation model with alternative decision policies, a (near) optimal solution can be reached.

REAL-TIME RESERVOIR OPERATION

Generally, the reservoir operation policy is developed taking into account the demands of the past and using data from historical or synthetic time series of hydrological variables. But the probability that an actual event will occur in the same way as prior events of the same type is small. A reservoir system can be efficiently operated if the time interval between the occurrence of an event and the execution of the control adapted for that event is short. In real-time operation, the release

DEVELOPMENT OF OPERATING RULES FOR SABARMATI SYSTEM

For judicious regulation of water resources in the Sabarmati basin, operation policies are required for conservation and flood control purposes for the various hydraulic structures. A detailed description of the Sabarmati basin was given in Chapter 1. A line diagram of this system is given in Fig. 11.17. The following discussion illustrates the application of systems analysis techniques to develop operation procedures for the reservoirs in this system. It also brings out the difficulties that

CLOSURE

Due to the increase in population and urbanization, the conservation demands as well as damage potential of floods are increasing day-by-day but it is not easy to create new reservoirs because of social and environmental ramifications. Therefore, it is essential to operate the existing reservoirs as efficiently as possible. Real-time operation is an efficient way of operating a reservoir system in which the control decisions are made on the basis of prevailing conditions of the system and the