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I I I I I I I I I I I I I I I I I I I User Manual - Consumptive Use Model o Conveyance Loss (CL) - The total of all the losses that occur from the diversion source (river head gate) to the farm head gate. These losses include seepage and evaporation. o River Head Gate Requirement (RHR) - The volume of waterrequired to fully satisfy the on-farm losses, potential evapotranspiration of the crop, and the conveyance losses. o On-farm Irrigation Efficiency (EO - The irrigation efficiency as measured from the farm head gate. o Conveyance Efficiency (Ec) - The ratio of the volume of water delivered in an open or closed conveyance system at the supply source that could be a head gate or well head. o System Irrigation Efficiency (Es) - The irrigation efficiency as measured from the point of diversion. This is the ratio of volume or irrigation water required for beneficial use in the specified irrigated area to the volume of water required to be delivered to this area to achieve the specified amount of beneficial use. 4.2 Miscellaneous Consumptive Use Terms o Basal Crop Coefficients (Kcb) - Represent conditions when the soil surface is visually dry so that evaporation is minimal, but the availability of soil water does not limit plant growth or transpiration. o Consumptive Use (CU) - In general, the estimated amount of water leaving a managed water system in a specified are because of human activity. o Deep Percolation - The amount of water that passes below the root zone of crops, exclusive of any upward movement of water from below the root zone. o Evaporation (Evap) - The physical process by which a liquid or solid is transformed to the gaseous state. In irrigation, evaporation is usually restricted to the change of water from liquid to a gas. o Evapotranspiration (ET) - The combined process by which water is transferred from the earth's surface to the atmosphere; evaporation of liquid or sublimation of solid water plus transpiration from plants. o Field Capacity - The moisture percentage, on a dry weight basis, of a soil after rapid drainage has taken place following an application of water, provided there is no water table within capillary reach of the root zone. This moisture percentage usually is reached within 2 to 4 days after irrigation; the time interval depends on the physical soil characteristics. o Leaching Requirement (LR) - The fraction of water entering the soil that must pass through the root zone in order to prevent soil salinity from exceeding a specific value. o Management Allowed Depletion (MAD) - Management allowed depletion is the maximum amount of water that is allowed to be depleted from the soil root zone without any perceived stress in the crop. o Mean Crop Coefficients (Kern) - Include wet soil effects after rain or irrigation on crop consumptive use, such as soil drying properties. o Reference Crop Evapotranspiration (Ref ET) - Reference crop evapotranspiration is the rate at which water, if readily available, would be removed from the soil and plant surface expressed as the depth of water evaporated and transpired from a reference crop such as grass (ETo) or alfalfa (ETr). Version J.J 20