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CRDSS <br />TASK MEMORANDUM 1.14-14 <br />Consumptive Use Model <br /> Enhancements to the Soil Conservation Service Blaney-Criddle for Use in the CRDSS <br />1.0 ISSUE <br />This document describes Soil Conservation Service (SCS) Blaney-Criddle (XCONS2) an d presents the <br />enhancements that are part of the consumptive use (CU) model. The CU model will also contain a daily <br />reference crop method (Penman-Monteith), but this document will only discuss the monthly Enhanced <br />SCS Blaney-Criddle (CRDSS CU). <br />ISCUSSION/ANALYSIS <br />2.0 D <br />Introduction <br />Two forms of the SCS Blaney-Criddle method will be available from the CU model, the SCS Blaney- <br />Criddle (XCONS2) and the Enhanced SCS Blaney-Criddle (CRDSS CU). SCS Blaney-Criddle <br />(XCONS2) is the same methodology used in the XCONS2 FORTRAN program developed by the U.S. <br />Bureau of Reclamation (USBR). The Enhanced SCS Blaney-Criddle (CRDSS CU) includes <br />enhancements to the XCONS2 methodology for the CRDSS. <br />SCS Blaney-Criddle as Presented in XCONS2 <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 the SCS Blaney-Criddle and <br />is 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). Some additional <br />modifications for XCONS2 were implemented, and this methodology will be referred to as SCS-Blaney- <br />Criddle (XCONS2). This method has been used by the USBR to prepare the Colorado River System <br />Consumptive Uses and Losses Report . <br />The original Blaney-Criddle research was published in Blaney et al. (1952), and later modified as TR21- <br />70. The development of the SCS Blaney-Criddle method is presented in Jensen et al. (1990). The basic <br />relationship used for the SCS Blaney-Criddle was developed for seasonal estimates. This basic <br />relationship assumes that evapotranspiration varies directly with the sum of the products of mean <br />monthly air temperature and monthly percentage of annual daylight hours for an actively growing crop <br />with adequate soil moisture. The implementation of this method will now include the soil moisture <br />characteristics and possible water supply limitations. <br />The Enhanced SCS Blaney-Criddle (CRDSS CU Model) <br />The Enhanced SCS Blaney-Criddle CRDSS CU method is a modification of the original SCS Blaney- <br />Criddle as implemented by the USBR in the FORTRAN program XCONS2. The main features added are <br />1 <br />A275 01.09.95 1.14-14 CSU IDS <br />