CRDSS_Task1_14-21_DifferencesBetweenXCONS2andCRDSSCU

• Title: CRDSS Task 1.14-21 - Consumptive Use Model - Differences Between XCONS2 and CRDSS CU ‎(XCONS2)‎
• Description: The Soil Conservation Service ‎(SCS)‎ Blaney-Criddle evapotranspiration estimation method implemented in the CRDSS consumptive use ‎(CU)‎ model and the original XCONS2 program have slightly different output results; this task memorandum identifies the source‎(s)‎ of difference between the programs.
• Decision Support - Doc Type: Task Memorandum
• Date: 1/9/1995
• DSS Category: Consumptive Use
• DSS: Colorado River
• Basin: Colorado Mainstem
• Contract/PO #: C153658, C153727, C153752
• Grant Type: Non-Reimbursable
• Bill Number: SB92-87, HB93-1273, SB94-029, HB95-1155, SB96-153, HB97-008
• Prepared By: Riverside Technology inc.

3.0 CONCLUSIONS AND RECOMMENDATIONS
The following conclusions are based on the different output (CRDSS CU program and XCONS2
program) for the computation of the crop evapotranspiration using the SCS Blaney-Criddle method:
1.The difference between the two programs is not related to the acreage difference in the input
data; the acreage is only an amplifying factor of the difference.
2.XCONS2 always gives lower values than CRDSS CU.
3.The differences in both programs originated from the computation of crop evapotranspiration
using the SCS Blaney-Criddle method.
4.Manual computations of the crop evapotranspiration for Delta5 (vegetables) showed better
approximation with CRDSS CU results, which means the problem seems to be imparted to the
XCONS2 program.
5.Different results seem to be related to the beginning and ending of the season. The subroutine
dealing with this aspect of the program takes into account the beginning and ending temperatures
for crops. It is suggested that the subroutine in XCONS2 dealing with the computation of
earliest and latest days of the season when the frost temperatures are given for a crop be more
closely evaluated if XCONS2 is used for future computations.
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A275 01.09.95 1.14-21 CSU-IDS