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Section 4 <br />Forecast of Future Water Demands <br />Forecasting water use (or water demand) is a critical part of the planning process. <br />Forecasts can range from simple projections based on anticipated growth in the <br />population to complex models using several variables to explain variations in water <br />use. Forecasts can be made f or a water system as a whole; however, forecasts are <br />considered more accurate when they are prepared for separate classes of water <br />users. For this reason, the demand forecasting developed f or Brighton evaluated <br />expected growth of daily, monthly and annual water demand f or each of the City's <br />customer types -residential, commercial, irrigation, municipal, and non-potable. <br />The potential effects of new water conservation efforts that will be selected during <br />this planning process have not been included in the demand forecast prepared <br />during this step. Demand forecasting at this point only developed future water <br />demand based on a continuation of the current and ongoing water conservation <br />efforts and "passive conservation' as older fixtures and appliances wear out and are <br />replaced with models that meet current efficiency standards. A revision to the <br />demand forecast based on implementing the planned conservation measures is <br />made later during the planning process, and is presented in Section 8. <br />Forecasting Method <br />To begin with, the forecasting methods that were developed f or this planning effort <br />focused on predicting future treated water demands and groundwater production <br />demands, given that known limitations of the water treatment plant capacity and <br />the groundwater production facilities will drive the development of water <br />conservation goals and the selection of measures and programs to implement. <br />Forecasting began by predicting total annual treated water demand based on the <br />following assumptions: <br />• Residential population serviced by the City was estimated to grow at about <br />1.0 % per year through 2013 and 2.5 % thereafter through 2020, based on <br />estimates developed by the Department of Public Works which were used to <br />forecast f uture water demands and infrastructure needs. <br />• Per capita residential water use was estimated to remain constant at 80 gpcd <br />(2005 gpcd was 78 and in 2006 it was 81). <br />• Total per capita water use was estimated to rise to over 170 gpcd by 2012 and <br />over 190 gpcd by 2017 (the City is currently at about 160 gpcd in 2007). This <br />increase in total per capita water use is primarily driven by expected <br />increases in commercial and irrigation water accounts, including municipal <br />parks irrigation. <br />City of Brighton Water Conservation Plan 9 <br />