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<br /> <br />Redwood City Public Works Services <br />Customer Water Use Website RFP <br />Attachment B – Water Budget Methodolgy 1 <br />Attachment B – Water Budget Methodology <br /> <br />Introduction: <br />This document represents the current methodology for calculating water budgets for landscape <br />irrigation and residential water utility accounts in Redwood City. This methodology is subject to <br />change due to changes in water supply, drought, state regulation, or local policy. Any system used <br />to calculate water budgets should be configurable by City staff with minimal intervention from the <br />software provider in order to meet the changing needs of the City. <br /> <br />Background: <br />Redwood City water budgets are based on the Landscape Coefficient Method that is the standard <br />of the Green Industry. It is endorsed by the Irrigation Association, California Landscape Contractors <br />Association, California Urban Water Conservation Council, and over 300 water agencies as the best <br />methodology for identifying and maximizing landscape irrigation efficiency. Water Budgets are <br />calculated daily for the previous day utilizing weather data retrieved from external web services. At <br />the end of a consumption period the water budgets calculated for each day in the period are added <br />to provide a sum total water budget used by the billing system. <br /> <br />Water Budget Definitions & Variables: <br /> <br />Variable Definition Redwood City Value <br />BUDGET = Volume of water budgeted for a given hydrozone area for a <br />given period. The overall water use budget for a site is the sum <br />of budgets over all hydrozones. <br /> <br />AREA = Landscape area irrigated in hydrozone (square feet). AT or AN or AW <br />AT Turfgrass area in square feet site measurement <br />AN Non-Turf area in square feet site measurement <br />AW Water Feature area in square feet site measurement <br />KS = <br /> <br />Species or plant factor relating a specific plant type’s water <br />requirements as a fraction of ETo. <br />KST or KSN or KSW <br />KST = Turfgrass water requirement default value 0.8 <br />KSN = Non-Turf water requirement default value 0.4 <br />KSW = Water Feature water requirement default value 1.2 <br />ETo = Reference evapotranspiration (inches) equals the depth of <br />water evaporated and transpired from a reference crop (4 to 7 <br />inch tall fescue grass) with an abundant water supply. ETo is <br />the “standard” measure of water needs from which other plant <br />types are compared via KS. Redwood City uses ETo from CIMIS <br />weather stations. CIMIS weather data is accessed through the <br />CIMIS Web API and REST Services more information is available <br />at http://et.water.ca.gov/ <br />by CIMIS <br />(period aggregate) <br />6.1.E. - Page 54