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<br />I <br /> <br />I <br />I <br /> <br />Consumptive Use Model Terms <br /> <br />I <br />I <br /> <br />4.0 <br /> <br />Consumptive Use Model Terms <br /> <br />I <br />I <br />I <br /> <br />The following consumptive use terms have been extracted from the CRDSS Task Memorandum 1.14-8. <br /> <br />I <br /> <br />4.1 Agricultural Consumptive Use Terms <br /> <br />. Potential Evapotranspiration (ETp) - The potential rate for a specific crop at which water can be <br />removed from the soil or plant surfaces, assuming the soil is full saturated. By applying a time <br />period to the potential evapotranspiration rate, a potential depth of irrigation water can be calculated <br />that is exclusive of precipitation or stored soil moisture required consumptively for crop production, <br /> <br />. Crop Coefficients - The ratio of evapotranspiration occurring with a specific crop at a specific <br />stage of growth to reference crop evapotranspiration at that time. This definition is not for the basal <br />crop coefficient K used in the Blaney-Criddle evapotranspiration at that time. Basal crop <br />coefficients represent conditions when the soil surface is visually dry. so that evaporation is <br />minimal but the availability of soil water does not limit plant growth or transpiration, whereas mean <br />crop coefficients include wet soil effects. <br /> <br />. Actual Crop Consumptive Use (CCU) - Crop consumptive use, often referred to as <br />evapotranspiration, is the total amount of water used for vegetative growth, transpiration, or <br />building plant tissue, plus the unavoidable evaporation of soil moisture, snow, and intercepted <br />precipitation associated with plant growth for any specified time and given water supply limitations. <br /> <br />. Effective Precipitation (EP) - Rain and/or snow that meets a portion of the crop's water <br />requirement. Effective precipitation does not include precipitation unused by crops such as surface <br />IUnoff and deep percolation past the root zone. <br /> <br />. Carry Over Soil Moisture (SM) - Moisture that is stored in soil pores in the soil's root zone during <br />the winter while the plant is dormant and becomes available to meet the consumptive use <br />requirements of crops during the growing season. <br /> <br />. Irrigation Water Requirement (IWR) - The depth of irrigation water required consumptively for <br />crop production, exclusive of effective precipitation and carryover soil moisture. <br /> <br />. Farm Loss (FL) - The total of incidental losses that occur during irrigation such as deep <br />percolation, IUnoff, and/or water applied for leaching. <br /> <br />. Farm Head Gate Requirement (FHR) - The depth of irrigation water, exclusive of precipitation, <br />stored soil moisture, or ground water that is required for other related uses such as leaching, frost <br />protection, etc. <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br />I <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />Version 1.1 <br /> <br />19 <br /> <br />Agricultural Consumptive Use Terms <br /> <br />I <br />