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the growing season, some perennial crops have multiple harvesting times. These will be considered with <br />crop coefficients. <br />While it is recognized that a number of climatological factors in addition to temperature (relative <br />humidity, wind movement, sunshine hours, tp and evaporation, etc.) have an effect on agricultural <br />consumptive use, the relationship for mean temperature alone is used by SCS Blaney-Criddle. It is <br />acknowledged that the SCS Blaney-Criddle is not the best method for including climatic factors; other <br />CRDSS methods (Penman-Monteith Equation) are more robust in their inclusion of climatic variations. <br />In order to include these variations in estimating consumptive use with SCS Blaney-Criddle, the crop <br />growth stage coefficients, kt and kc, are included. <br /> k = kt x kc . . . . . . . . . . . . . . . . . . (3) <br />where kt = 0173t -.314 (a climatic coefficient that is related to the mean air temperature (t)), and kc is a <br />coefficient reflecting the growth stage of a crop where values are obtained from crop growth stage <br />coefficient curves. <br />The USBR XCONS2 Program <br />Introduction <br />The form of the Blaney-Criddle equation used in XCONS2 is the original Blaney-Criddle equation with <br />modifications adopted by the SCS. This method is commonly referred to as SCS Blaney-Criddle and is <br />described in the U.S. Department of Agriculture Soil Conservation Service's Irrigation Water <br />Requirement, Technical Release No. 21, revised September 1970 (TR-21) (USDA 1970). <br />Effective Precipitation <br />XCONS2 uses two methods for computing the effective precipitation from total precipitation data. The <br />first method is the SCS method as described in the TR-21, where the calculated effective precipitation is <br />a function of the irrigated application depth, total precipitation, and monthly consumptive use. The <br />second method is the USBR method, where the effective precipitation is a function of total monthly <br />precipitation. The monthly and annual consumptive irrigation requirement for different crops can be <br />calculated using the TR-21 method. This method considers consumptive irrigation requirement as equal <br />to the total monthly consumptive use minus the effective precipitation. <br />Also, project consumptive use, the effective precipitation, and consumption irrigation requirement can be <br />computed for each type of crop in the study. Up to 100 years of weather data can be processed with <br />XCONS2. Multiple weather stations can be used with weighted values denoting data reliability. <br />XCONS2 computes the monthly mean air temperature and monthly total precipitation for each year. <br />Input Data Files <br />XCONS2 uses an ASCII, pre-formatted type of input data file. The required input data file includes a <br />title for the run, the type of output format, each crop's seasonal growth data, the number of crops in the <br />study, the number of years of study, daylight hours, monthly mean air temperature, and total <br />precipitation. These data should be entered in the input data file in a particular format, including the <br />correct row and column for each entry. XCONS2 creates an ASCII output file with extensive information <br />2 <br />A275 01.09.95 1.14-7 CSU IDS <br />