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Water Budget Formula <br />Water Budqet Definitions & Variables: <br />Variable <br />Definition <br />Redwood City Value <br />BUDGET <br />Volume of water budgeted for a given hydrozone <br />= <br />area for a given period. The overall water use <br />budget for a site is the sum of budgets over all <br />hydrozones. <br />AREA = <br />Landscape area irrigated in hydrozone (square <br />AT or AN or Aw <br />feet). <br />AT <br />Turfgrass area in square feet <br />site measurement <br />AN <br />Non -Turf area in square feet <br />site measurement <br />Aw <br />Water Feature area in square feet <br />site measurement <br />Ks = <br />Species or plant factor relating a specific plant <br />KsT or KSN or Ksw <br />type's water requirements as a fraction of ETC. <br />KST = <br />Turfgrass water requirement default value <br />0.8 <br />KSN = <br />Non -Turf water requirement default value <br />0.4 <br />Ksw = <br />Water Feature water requirement default value <br />1.2 <br />ETo = <br />Reference evapotranspiration (inches) equals <br />by CIMIS <br />the depth of water evaporated and transpired <br />(period aggregate) <br />from a reference crop (4 to 7 inch tall fescue <br />grass) with an abundant water supply. ETo is the <br />"standard" measure of water needs from which <br />other plant types are compared via Ks. Redwood <br />City uses ETo from CIMIS weather stations. <br />CIMIS weather data is accessed through the <br />CIMIS Web API and REST Services more <br />information is available at http.//et.water.ca gov/ <br />ERain = <br />Effective rainfall (inches) equals the depth of rain <br />by WeatherUnderground <br />effective in offsetting ETo for each hydrozone. <br />(period aggregate) <br />Effective rainfall varies widely with rainfall <br />frequency, magnitude, time of year, and root <br />zone depth. Redwood City uses rainfall data <br />from Weather Underground (WU). WU data is <br />accessed through the WU API more information <br />is available at <br />http://www.wunderground.com/weather/api <br />NIR <br />Net Irrigation Requirement: The amount of water <br />Function >= 0 <br />required in a hydrozone that is not provided by <br />rainfall. NIR is calculated for each day, based on <br />Page 36 of 38 <br />AM/AGR/2017.104/SMART ENERGY SYSTEMS—CUSTOMER WATER USE PORTAL <br />REV: 05-15-17 MI <br />