Demands for both the "base" (General Plan) growth level and the "Central Area High Density" level were developed by applying sector-based water use factors to housing unit and non-residential acreage figures provided by MAG. The water use factors were derived by the city's Finance Department from records of billed water use over the period 1989 through 2000, and included a variety of both wet and dry years. Adjustments were made for lost water (typically in the 8 to 9 percent range) and other minor factors.
In evaluating the scenarios, several conclusions were derived:
- Existing customer demands can be met under both normal and moderate shortage conditions for the entire 50 year period.
If Phoenix demand was to stabilize at current levels, no further capital expenditures would be necessary for water supply acquisition and for the development of related infrastructure. Even under severe shortage conditions (which are likely to be very infrequent), existing customers could adapt by reducing water use by approximately 10 percent for the duration of the severe shortage.
- Projected demands under both base (General Plan) and high density development levels can be met with a combination of current and future supplies in both normal and moderate shortage conditions for the entire 50 year period.
This conclusion assumes that all current and future supplies are available for service to customers. Under high density conditions, a potential gap of up to 10 percent may exist under moderate shortage conditions beginning in 2030, though increased conservation, lower than expected use rates or relatively minor drought-based demand reductions would eliminate this gap.
- Under severe drought conditions, a combination of customer demand reductions and supplemental supplies would become necessary.
The most significant needs would occur in the high density scenario where a nearly 30 percent gap could develop between supplies and demands. This gap could be achievable on a short term (1-2 year) basis with demand reductions alone. Extended severe conditions (which are highly unlikely) would necessitate deployment of supplemental supplies.
- Deployment of future and supplemental supplies will entail significant capital expenditures to be phased in over time.
Plans for deploying these supplies will need to be developed. Costs will be incurred for supply acquisition, the drilling of new wells, wellhead treatment facilities, reclaimed water treatment facilities, transmission lines, recharge facilities and a host of other related features.
