| Summary: | The cost-effective method is utilized for comparing a multipurpose water resource design with a group of equally effective single-purpose designs in the floodplain of Arcadia Watershed in Tucson, Arizona. The multipurpose water resource design is an integrated water-related recreation facility bordering Arcadia Wash providing flood control, irrigation, and recreation benefits. The single-purpose designs are a flood detention facility, park and lake which provide the same benefits as the multipurpose design, but are apart. The multipurpose design reduces a 50-year summer thunderstorm flood flow from 1700 cubic feet per second to 1078 cubic feet per second by diverting a portion of storm runoff from Arcadia Wash and routing it over grass and through a lake. The use of storm runoff in place of city water in the multipurpose design for irrigation and the lake reduces annual water costs by about 60 percent and total annual costs by about 10 percent as compared with the single-purpose designs. The multipurpose design is clearly more cost-effective as shown by its lower annual cost, namely $134,600 versus $197,000 for the single-purpose facilities. Reductions in land price substantially reduce the cost-effective advantage of the multipurpose design.
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