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<br />.' , <br /> <br />. <br /> <br />e <br /> <br />. <br /> <br />OOU04 <br /> <br />Task 1.14 - Evaluation of Consumptive Use Models <br /> <br />2.2 The following are miscellaneous consumptive use tenns: <br /> <br />Basal Croo Coefficients (Kcb) <br /> <br />Basal crop coefficients represent conditions for when the soil surface is visually dry, so <br />that evaporation is minimal but the availability of soil water does not limit plant growth or <br />transpiration. <br /> <br />Consumptive Use (CU) <br /> <br />Consumptive Use (CU) in general is the estimated amount of water leaving a managed <br />water system in a specified area due to human activity. There are a few assumptions that are <br />acknowledged along with this definition: <br /> <br />1. Water in the upper-basin diverted outside of Colorado's Western Slope water system is <br />assumed not to returned to the system in any way. <br /> <br />2. Some portion of what might be considered water use will not be consumptive use. In <br />other words, some port~on of the water delivered to a municipal area or irrigated field <br />will return to the system in the form of treatment center discharges, sewer run off, <br />groundwater recharge and/or precipitation. Where possible these amounts will be <br />included in CU estimates for the CROSS CU model. <br /> <br />3. The selection of a small area for the calculation of consumptive use may not be able to <br />account for all the interactions of water injection and withdraw from the area's water <br />system, <br /> <br />Deep Percolation <br /> <br />Deep percolation is the amount of water which passes below the root zone of crops, <br />exclusive of any upward movement of water from below the root zone. <br /> <br />Evaporation (Evap) <br /> <br />Evaporation is the physical process by which a liquid or solid is transformed to the <br />gaseous state. In irrigation evaporation is usually restricted to the change of water from <br />liquid to a gas. <br /> <br />Evapotranspiration (E1) <br /> <br />Evapotranspiration is the combined process by which water is transferred from the earth <br />surface to the atmosphere; evaporation of liquid or sublimation of solid water plus <br />transpiration from plants. <br /> <br />Field Capacity <br /> <br />Field capacity is the moisture percentage, on a dry weight basis, of a soil after rapid <br />drainage has taken place following an application of water, provide there is no water table <br />within capillary reach of the root zone. This moisture percentage usually is reached within <br />two to four days after an irrigation, the time interval depending on the physical <br />characteristics of the soil. <br /> <br />10/6/94 - CU Model Terms (1,14-8) <br /> <br />3 <br /> <br />IDS Group. CSU <br />