WSPC04493

• File Number: 8283.200
• Description: Colorado River Basin-Colorado River Computer Models-Colorado River Decision Support System-Ray
• State: CO
• Water Division: 5
• Date: 8/25/1995
• Title: Consumptive Use Modeling-Task Memorandum-Phase III-Analysis of the Bear Report Blaney-Criddle Crop Coefficients
• Water Supply Pro - Doc Type: Report/Study

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of Etr using the 1972 Kimberly Penman are about 7% lower than seasonal estimates using the
Penman Monteith.

The results of the analysis for Gunnison, Steamboat Sprlngl, Maybell and Delta are shown
In the attached Table 4. The analysis for each of the Itatlonl II Ihown In Table 8. For
determination of potential evapotranspiration, ths May through August period i. probably mOlt
critical, with accuracy In June and July being of the molt Importance. The ratio. for the Randolph
and Hilliard ,Ites are reasonably good for the critical period snd ecceptable for June and July. The
Hilliard Iyslmeter site IElev. 75501 was highar than the Randolph .Ite IElev. 62801. However, the
results do not show that the Hilliard coefficients ere more repre.entatlve at higher elevationl thin
the RandOlph.

TABll .
llAno OF SC8.BC CORRECTED COEFFICIENTS TO tall" BEAR RIYER 'C..IC COEFACIENTS
COLORADO BEAR RIYEA MAY JUN JUl AUCI IEP OCT
LOCAnON L Y81METElI
Gu"nlean Montpelier 0.89 1.21 1.34 1.04 0.S8 1.11
Randolph 0.S2 1.011 1.12 0.81 0.78 0.70
Hilliard 0.8& 1.10 1.111 1.00 0.84 0.88
Sleemboat Montperier 1.10 1.12 1.S2 1.18 0.82 1.S0
Springe
Randolph 1.01 1.0S 1.10 1.01 O.Sl 0.12
Hilliard 1.17 1.14 1.1& 1.12 0_80 1.12
MaybeH Montpelier 1.27 1.11 1.11 0.8e 0.92. 1.08
Randolph 1.18 0.8' 0.83 0.111 0.82 0.18
HHHard 1.3. 1.03 0.87 0.'& 0.81 0.84
Oa~1 Monrpeller 1.24 1.04 1.07 0.84 O.Sl 0.83
Aandolph 1.13 0.81 O.BB 0.12 0.72 0.52
Hilliard 1.32 0.8' 0.112 0.80 0.78 0.72

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3..& SUMMARY/CONCLUSIONS

For determination of the ditCh diversion demands In the CROSS modeling, the Hill SCS-BC
coefficient .s determined at the Randolph and Hilllerd IYllmeters are recommendeifor use Instead
of the SCS-BC coefflclentl in TR.21. The Montpelier coefficienta IIr. not recomn/anded because
of the appearance of e locellzed impact on the coefflclente caused by nearby_ lakes.

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Analysis at each of the NWS in the CROSS simll.r to the analysis uaed herein would Identify which
Bet of coefficients to use at sny particular station. In lieu of that type of analysis, it Ie
recommended that an average of the Randolph Ind Hillierd SCS-BC coefficients be used.

The growing nlson Is approximately 150 to 170 deys. The growing season at Maybell IElev.
5970) Ind Delta IElev. 49301 is 179 end 201 day., respectively. The growing .eeson at Delta
starts a month earlier than the growing season at the Bear River Itations. Hill's analysis did not
provide a coefficient for April. Because of the length of the growing season, lack of In April
coefficient, and the ratio shown in Table 4 for Delta, it Is recommended that the coefficients not
be uled It elevations below 5900 feet.

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A .111 WALTER

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