the objective has been determined, our methodology leads to the selection
of that combination of structures, levels of development for different
water uses, and operating procedures that will best achieve the objective.
— Arthur Maass (Design of Water Resources
methods of water-system design developed by an interdisciplinary team at
Harvard University are best known for their influence on the study of the
feasibility of new water projects. However, as the quotation from
Professor Maass, the principal author of "Design of Water Resource Systems," shows, the concept of objective-based design can be applied to operating
procedures as well.
In this step, the Drought Preparedness Study (DPS) team compares proposed
alternatives against the status quo, measuring how well they meet the
objectives developed in Step 2 (i.e., Develop Objectives and Metrics for
Evaluation). The team will
eliminate or redesign alternatives that do not measure up until they are
ready to recommend a plan to decision makers.
Economic and Environmental Principles and Guidelines for Water and Related
Land Resources Implementation Studies" (P&G) list four characteristics
of good plans. These characteristics are general enough that they are
appropriate for federal or non-federal planning efforts:
- Completeness: all
the elements required to make the plan work are included in the plan.
- Effectiveness: the alternative addresses the planning objectives.
- Efficiency: the
ratio of plan outputs to inputs is satisfactory.
- Acceptability: the plan satisfies decision criteria and does not violate planning constraints.
The initial screening of
alternatives should emphasize effectiveness and
acceptability. Table 7 illustrates how this initial screening can be
using decision criteria, planning objectives and constraints.
The goal of the initial screening is to eliminate some
alternatives and develop a ranking of the remaining
alternatives. The process of ranking may help in the continuing effort
communicate and clarify objectives and criteria. The initial
screening permits the focusing of study resources on
the detailed evaluation of the most promising alternatives.
Table 7: An Initial Screening of Alternatives
Alternative Plan Number
Is the Plan Complete?
Meets Planning Objectives?
Meets decision criteria
Does not meet water quality objective
Does not increase hydropower production
Should greatly help M&I, may hurt river recreation
of the alternatives being seriously considered should now be
the shared vision model. In some cases, teams may decide that
alternative should be represented by a separate model (a
the status quo model saved with a different file name). In
other cases, teams may decide that alternatives can be more
effectively represented by internal “switches” in the status
which effects the desired change in water management
procedures. The models provide the plan performance and outputs required
detailed evaluation. Using
the model, the next level of evaluation can be on the basis of
measures. For example, the
model can be used to estimate how much more frequently would a
to impose curtailment under an alternative than under the
status quo. Table 8 provides a more detailed evaluation of alternatives
the status quo is compared to two other alternatives.
Table 8: A More Detailed Evaluation
an evaluation using just performance measures is enough. If operational
changes can be made that benefit many users and hurt none (including the
environment), and the value of the benefits clearly outweigh the
administrative costs of instituting the changes, then an evaluation of the
economic and social effects of each alternative is unnecessary. But what
if there is an alternative that benefits some users and hurts others? Or
what if an alternative helps everyone but has a significant financial
cost? In those cases, an evaluation of the economic, environmental and
social effects of the alternatives is the only way to determine which
alternative best addresses the goals and decision criteria.
of alternatives should lead to tentative recommendations from the DPS
factors to consider during alternatives analysis are how to capture the
risk and uncertainty inherent in each alternative and incorporate this
information into the shared vision model.
definitions of the terms risk and uncertainty as they are applied to water
resources management have changed a little over time. Risk refers
to some negative consequence with an associated probability, even if that
probability is difficult to calculate. Risk in water resources management
has until recently been defined as the product of the consequence of
events multiplied by the probability of the events, that is to say, as an
expected value of damages (Guidelines For Risk, 1992). The classic
definition of uncertainty involved those unknowns that could not be
expressed in probabilistic terms. In flood damage reduction studies, risk
which is an expected value of the damage from extreme but rare floods can
be compared to annual or present day costs to determine if it would be
cost effective to reduce residual flood damages even further by increasing
the size of the flood control project. In strategic water supply studies,
the “rare, large event” is the drought, and the risk associated with
any strategic supply plan is the product of the expected consequences of
future droughts times their probability.
research and experience has shown that people react differently to the
risks of a low probability, high consequence event (a 500-year flood, for example)
and a high probability, low consequence event (a 2-year flood), even
though they may have the same expected value (Guide Book for Risk
Perception and Communication, 1993). Thus a more useful definition of risk
has come into use that does not multiply damage by probability: risk is
the expression of an undesirable consequence in terms of the probability of
The concept of risk in tactical drought contingency plans
has much in common with the risks associated with flood
that are used to minimize damage from floods larger than the
Risks in drought management include: the risk that a very
will cause a catastrophe;and the risk that the drought
response plan will be
triggered too often (risking reduced effectiveness of public
in subsequent droughts) or too late (eliminating water
savings that would
have been possible had the response been initiated sooner).
Both of these risks can be assessed using the shared vision model. No
simple quantification, however, will generally be possible
because of the various combinations of severities and
droughts. Nonetheless, the
use of tools such as the Drought Atlas and simulations with the shared
vision model can develop a better informed sense of the risk that can be
more clearly communicated to decision makers and elected officials.