AgdaPkt 2004-01-26 - Laserfiche WebLink

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~ "'.' ,'=""".~.,..., A' _"",_.,.,.;:;,:-".;;:""~,,,~,"fIl<il':',]':A.~"~;X*" )(;J~,l2f;;~;;'pTtV; , 5.lt-32. I RWC Water Supply ReUabWty 0 Bay Area Water Usm,Usoc:iation, Interim Water Shortage Allocation Plan, July 2001. 0 Nicole M. Sandkulla, p, E., Bay Area Water Users Assooiation (BAWUA). Prom this information 1 generated Exhibit Isbowing the CUtTent lcvelofwater supply reliability for RWC. Because the future is unknown, reliability must be expresscdin probllbilistic tenns using the best information available, It is important to note that as part of the 1984 Master Water Sales Contract RWC has a contractual "water supply assurance" of 12,243 acre-feet per year ' (MY). However, this amount relates toa legal definition and:not an absolute volume guaranteed. In times of shortage, the SFPUC will provide 1es$ than the assurance as illustrated in Exhibit 1. Exhibit 1. SFPUC Water Supply Reliability (1) (2) (3) (4) 45) (I) HItch Halcby BAWUA RWC RWC Future SylltamOemand Demand DaftWld A1locatlon H1$torlcal Probability Scenario CutbGk Cutback Cutback AFY PlObabllIty 2010 1 0% 0.0% 0.0% >12;243 NA NA 2 -5% -6.4% ~12.2% 11,6114 NA NA 3 -10% ~12.0% -1H% 10.891 7.6% 6.3% 4 -15% -18.2% -23.3% 10,124 NA 5.1% 5 -20% -23.6% -28.4% 9,456 2.5% 2.5% 6 ~20% >-23.6% >-28,4% <9.456 O.Q'I'. 2.5% (1) Thelnlllrim Walsr $1ong. AIfocaIIon PlaIlllddresses syslam wide CUlbadcsuplo 20%. (2) Velue. provided by Nk:oIe SanclkuIIe, Bey I\!'A Waler Use<i~. (3) !lased on WOIIIsMaI. !rIlmNIcda SandJwUa. upda..s wI1h FY 1999/00 and 2OOllfOt water LISe. (4) ElaIl6d on FY 2000101 __ usetQlals. (5) F'rnbabiIIty 01 NCh scenarlo aGaII'I"llln. QMlIl year based on Il)'d~ fr'om 11121 Ie 1999. Inlotr'nation taken 'from f"1\IIR 2-S In Sl'i'UC Weier S\lIlPIY Moslar Ptan,1\pil20DO. The probability of a 5% and 15% c:u\b8d<S not acIdJ8ssed. hance reponed as not 8'l/ll1lallle (NA). (6) FUlIlre Ilfllbabltiti8s bu8d on I~ ofllle:<eo anll32S MGD eem.ncl ~ In Illulerplan. Exhibit 1 shows that the frequency and magnitude of water use cutbacks. From a statistical perspective, given cum:nt circUtnSl3nces in a given year there is a: a 89.9% chance of no water shortage or a S% cutback. UnfortunateJy, the SFPUC master plan did not identify the probability of a 5% cutback. For San Francisco and most BA WUA agencies, II 5% system cutback will be a minor event met with voluntary conservation. For RWC, in contrast, a 5% system cutback will lead to a 12.2% RWC cutback-a significant event requiring some active conservation interventions. Pag1!Z