14
I.
Introduction
Operation of a water resources system, on the other hand, is concerned
with what decisions are necessary to best accomplish the objectives of an
existing system. While the operation of an existing water resources system
may be considered disjointly from the planning function, the planning for
the expansion of an existing system definitely must encompass the hypothesized future operation of the system. From the viewpoint of this
book, operation is concerned with the optimization of an existing system,
whereas planning attempts to formulate an optimal system by possible
additions of elements to the existing system.
Because, as noted earlier, water resource development has changed in
the last few decades from simple single-purpose projects to multipurpose
programs involving large river basins, optimum planning, design, and
operation can best be obtained through the use of mathematical models
and high-speed digital computers. An analytical model, of course, incorporates many simplifying assumptions to make the model manageable.
Even after many simplications, voluminous data are required to provide
the coefficients and inputs for the mathematical model. Such data are often
not available, nor are there adequate personnel to formulate and solve
models. One must be wary that the models used do not become so simple
that they no longer reflect the real physical system of the river basin. Some
models are so rigid and mechanical that they cannot include the social
benefits and costs of projects. Other models do not represent well the real
river basin. Consequently, the analyst must be wary of attaching to a
model a general aura of validity that it does not merit.
Once the five phases of systems analysis described above have been resolved, or at least partly resolved, two main routes can be pursued to
realize the objectives for the system being planned, i.e., what is best in regard to the configuration of system elements and its operational policy.
The two methods are simulation and optimization; see Fig. 1.6.
Simulation carries out "experiments" on a model of the system to obtain* data that can be evaluated to determine the best operating policies
[Ackoff, 1961; Hillier and Lieberman, 1967; Hufschmidt and Fiering,
1966]. Simulation was the first technique to be used by systems analysts
in solving complex water resources problems. It was successful in examining
the Nile Valley irrigation plan [Morrice and Allan, 1959], in planning for
the augmentation of the Sydney, Australia water supply (1969), and in
energy studies on the Columbia River [Lewis and Shoemaker, 1962], The
general procedure is to run case studies in which the operational parameters
are varied for a number of preselected cases. Computer programs for a
single case can be readily adapted to the case-study technique. One of the
advantages of the case method is that it is not concerned with whether the
I.
Introduction
Operation of a water resources system, on the other hand, is concerned
with what decisions are necessary to best accomplish the objectives of an
existing system. While the operation of an existing water resources system
may be considered disjointly from the planning function, the planning for
the expansion of an existing system definitely must encompass the hypothesized future operation of the system. From the viewpoint of this
book, operation is concerned with the optimization of an existing system,
whereas planning attempts to formulate an optimal system by possible
additions of elements to the existing system.
Because, as noted earlier, water resource development has changed in
the last few decades from simple single-purpose projects to multipurpose
programs involving large river basins, optimum planning, design, and
operation can best be obtained through the use of mathematical models
and high-speed digital computers. An analytical model, of course, incorporates many simplifying assumptions to make the model manageable.
Even after many simplications, voluminous data are required to provide
the coefficients and inputs for the mathematical model. Such data are often
not available, nor are there adequate personnel to formulate and solve
models. One must be wary that the models used do not become so simple
that they no longer reflect the real physical system of the river basin. Some
models are so rigid and mechanical that they cannot include the social
benefits and costs of projects. Other models do not represent well the real
river basin. Consequently, the analyst must be wary of attaching to a
model a general aura of validity that it does not merit.
Once the five phases of systems analysis described above have been resolved, or at least partly resolved, two main routes can be pursued to
realize the objectives for the system being planned, i.e., what is best in regard to the configuration of system elements and its operational policy.
The two methods are simulation and optimization; see Fig. 1.6.
Simulation carries out "experiments" on a model of the system to obtain* data that can be evaluated to determine the best operating policies
[Ackoff, 1961; Hillier and Lieberman, 1967; Hufschmidt and Fiering,
1966]. Simulation was the first technique to be used by systems analysts
in solving complex water resources problems. It was successful in examining
the Nile Valley irrigation plan [Morrice and Allan, 1959], in planning for
the augmentation of the Sydney, Australia water supply (1969), and in
energy studies on the Columbia River [Lewis and Shoemaker, 1962], The
general procedure is to run case studies in which the operational parameters
are varied for a number of preselected cases. Computer programs for a
single case can be readily adapted to the case-study technique. One of the
advantages of the case method is that it is not concerned with whether the