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<br />II . , " ,. - <br /> <br /> I <br /> <br />I <br />1. Objective and Approach <br />The objective of the re;sem:h described in this report is to develop water Wi. forecasts for <br />the City of Redwood City (RWC) forthe20-year period 2000 to 2020. The re¡¡ulting <br />water use forecasts canasllistRWC with a variétyofwa~planning decision¡¡/functÎons, <br />including suppørtingthe.decísion-malcing ,process underlying construction of water <br />recycling facilities in the Rl:dwood Sho¡es area. <br />A variety of methods arc availaþle to forecast water use. ThCI'e are pros and cons <br />associated with each, and data avl!ilability is o~en an important selection detenninant. <br />PœviQusly, RWChuusl:\d, simple extrílpQlation metbQds for water use forecasting. This <br />approach has minimal data and analytic requiIeme¡¡ts, but an extrapolation of the past is <br />not necessarily the best predictor oftbe future. <br />Because RWC has a~ilable several key sources ofinfonnat1un regarding future drivers <br />of w¡¡ter use (e.g., housing JmÍts and employment), it is logical.to make use of this <br />infonnation as is done via the føllowing $ÙJgle variable mode]: <br /> WATER.,. = DRlVER,,). COEFFICŒNT.. <br />where <br /> WATER." = wateruseofscctOr s in time t <br /> DRIVER,,) - data driver of seclOr S in time t <br /> COEFFICIENT... = water use per driver coefficient of sector s in time. t <br />In RWC's case there arc seven sectors identified in the bíIIing system as follows; <br />. single family residential <br />. multiplelìunily residential <br />. commercial <br />. cQmmercíal1rrigation <br />. gov~ment <br />. other <br />. residential irrigation <br />Ail described in Section 2, the data drivelS are number of housing units for the residential <br />_tors, number of employees for the commercial ~tors, and population for the otber <br />sectors. Section 3 de$cribea Che deve!øPment ()ftbe coefficients that are based on <br />historical water use correlations, as p°tenti¡;lIy adjusted f()t weather, water prices, and <br />expected water conserv¡;tion transfonnanòns. Once the data drivers and their associated <br />coefficients are identified, water use forecasts over a 2O-year period are developed as <br />described in.Sectiop4. Lastly, Section 5 describes seusitivityanalYSes oftb.cwaler use <br />foreca$tS to underlyingas$1JIIJptiolls. <br /> Page 3 <br />