Laserfiche WebLink
I C- 31 <br />RWC Water Supply RaMility <br />• Bay Area Water Ustxs.Assoclation, Interim Water Shastage Allocation Plan, Iuly 20(11. <br />• Nicole ILL Sindkulla, P. E., Bay Area Water Users Association (BAWUA) <br />From this information I generated Exhibit I showing the anent level of water supply reliability <br />far RWC. Because the future is unknown, reliability must be expressed in probabilistic terms <br />using the best iafmrnation available. It is important to Oft that as part of the 1984 Master Water <br />Sales Contract RWC has a contractual "water suppiy,assunmce" of 12,243 acre -feet per year <br />(AFY). However, this amount relates to•alegal definition and not an absolute volume <br />guaranteed. In times of shortage, the SFPUC will provide less than the assurance as illustrated in <br />Exhibit 1. <br />Exhibit 1. SFPUC Water Supply Reliability <br />icy i vc 45) <br />(a) <br />Hatch Ftet ttavw RWC a <br />FvWn <br />Syaumnamand Demand Wmand Aaoeanon FQStadW <br />Probaraaay <br />seensdo Cutback Cutback Cudmk AFY Probabift <br />20t0 <br />1 0% 0.0% OA% >12,249 NA <br />NA <br />2 -5% -6.4% -122% 11,564 NA <br />NA <br />3 -10% -12.0% -174% 10.891 7.6% <br />53% <br />4 -16% -1a.2% -293% 10.124 NA <br />5.1% <br />5 -20% -23.6% -28.4% 9,456 2.5% <br />2.5% <br />6 >-20% -23.6% ?-26.4% c9.456 OA% <br />25% <br />(1) The Interim Water Shoaopa Aaoealion pion addrena system wide anbscla up W 2016. <br />(2) Vakma provided by Nioda Sardau6a, Bay Ana Wow WaagwoWaon <br />(3) Based on werKetwm from Maio Sanftft upd&W MM FY 1696100 and 2000!01 water use. <br />(4) Based on FY 2700101 wmer m W a L <br />(5) Pmb"ty of each aoenmlo ocadkip In apkm VW based on bydMkWf om 16121 10 1998. <br />Inlormabon taken from Fipun 2.5 io SFPUC Wmm supply Master Pion, Apr620W. <br />The probah6lty of a 5% and 13%09eaeln not adyesaed, hWM MMW a not avaaable (NA} <br />(6) Futtae probamG6es baud on MlerPoka oo of On 260 and 715 MOD dward wenarics In mapanptm <br />Exhibit 1 shows that the frequency and magnitude of water use cutbacks. From a statistical <br />perspective, given current circumstances in a given year there is a: <br />a 89.9 chance of no water shortage or a 5% cutback Unfortunately, the SFPUC master <br />plan did not identify the probability of a 5% cutback. For San Francisco and most <br />BAWUA agencies, a 5% system cutback will be a minor event met with voluntary <br />conservation. For RWC, in contrast, a 5% system cutback will lead to a 12.2% RWC <br />cutback —a significant event requiring some active conservation interventions. <br />Page 2 <br />