The least-cost planning process gives all available options an equal chance in the selection process. If any options, demand management or supply augmentation, are arbitrarily excluded, it becomes unlikely that the selected plan will cost the least. Using this criterion does not mean that planning decisions must be limited to evaluations that translate all costs into dollar amounts. The LCP concept can be incorporated into evaluations that rely on relative rankings of social and environmental impacts as long as the units of measurement used are consistent and the criteria for assigning values are clear. However, when social and environmental consequences of alternatives can be reasonably expressed in dollars, identifying the preferred plan will be less subjective.
With LCP, the water manager's objective becomes one of meeting all water-related needs of customers, not one restricted to looking for ways of providing additional supply. For example, if a growing service area's need for additional water can be reduced with an ultra-low-flush toilet retrofit program rather than additional water supplies, then the retrofit program should be considered on its merits and compared with all other options when putting together a water management plan.
In addition to its focus on considering all feasible options for meeting customers'
needs, the LCP process requires systematic and comprehensive evaluation of
all costs associated with each option when devising alternative plans, including
the costs of not fully meeting the customers' needs at all times and planning
for some probability of shortages. The option of planned periodic shortages
must be as carefully evaluated as any other. (Plans which would result in extreme
shortages jeopardizing life or health would, of course, be unreasonable.) Expressing
this valuation in a way that can be used in a reliability model is often problematic.
While some of the losses can be quantified (for example, the cost of lawn replacement),
others, such as the loss of aesthetics, environmental cooling, and inconvenience,
are difficult to measure.
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