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<br /> -"---~. =-, -'t)"~'i4~11\~:~r:~';r~;1t" <br /> I 5.\c'.l3 <br /> In cakulating total system water demands, we factor in a 4% increase to reflect <br /> unaccounted for water in the distribution system; it equals the difference between the <br /> water put into the water distribution system and total billed water use. Fortm:: cale:ndar <br /> year 2000, tbismass balance accounting shows unaccollnted for water use equals 4.4%. <br /> For the future years, the fon:c:ast calculation asswnes unacoountcd water use wiD be <br /> 4.0%. Having an \1nllcx:ounted. for factor of about 4.0% is relatively good. Comparable <br /> water systems typically experience unaccounted water ii'omS to 100,4. <br /> 5. Sensitivity Analysis <br /> This section explores how variations in assumptions can impact ~. base case point <br /> estimates generated in Appendix D. Specifically, we looked at water use intensification <br /> and weather variation. <br /> 5.1 Water Use Intensification <br /> Increasing residential and commercial space costs can lead to 1ntCl1l$ification ofuseatan <br /> existing site. Apartments, for example, can ,secmorepersons per unit as higher rent costs I. <br /> cause more people to livetoget:berto make the rent. Similarly, business owncn&nl <br /> financially motivated to put mote employoes per square foot to managecoBls. ~ <br /> I <br /> We tested the hypothesis ofinteD&ification by comparing FY.1997/98 water use to FY <br /> 2000101 water use. We found that water use did 1ncrcase by about 8 percentoiu water <br /> use per bill basis for bo1h multiple family and commercial customcts. This held trIlC for <br /> winter as well as annual water use (weather is not likely to cause this change). <br /> Although this evidence supports water use intensification over the 4-ycar period, it does <br /> not necessarily mean it will continue in the ibturc, In fact, prices in the real estate market <br /> have decreased in recent months. Tbe:reforc,for the pwposes of forecasting, we assume <br /> that the intensification levels experienced in 2000 will remain constant over our 2O-yca.r <br /> planning horizon. <br /> 5.2 Weather Variation <br /> RWC's annual water demand only varies by about +/- 2 percent as a result of weather. <br /> This conclusion is drawn ftom 8I1a1ysis of statistical regression models of monthly water <br /> purchases as a function ofwcather between 1975 and 2001. Note weather can <br /> significantly impact RWe's water supplies via the Retch Hetcby water system; shortages <br /> in supply can consequently require RWC to take actions to ,cut water demands (e.g., <br /> 1991). Absent supply shortages, however, RWe's annual water demand does not vary <br /> greatly because of local weather. <br /> This lack of variability in annual water use is largely a function of the lack of variability <br /> in annual temperatures. Over the 1948 to 2001 period, about 70 percent of the time , <br /> r <br /> t <br /> f <br /> Page 7 t <br /> " <br /> r <br /> f <br /> --~--.._..._-.-- <br />