CRDSS_Task1-5_VariableEfficiencyEvaluation_Compare

• Title: CRDSS Task 1.5 - Variable Efficiency Evaluation - Compare StateMod Variable Efficiency and Soil Moisture Accounting Historic Model Results to Previous CRDSS Model Results and Historic Measurements
• Description: The purpose of this task was to run the monthly Historic Yampa River Basin model with the irrigation requirement file ‎(*.ddc)‎ created in Task 1.2 and the baseflows developed in Task 1.3.
• Decision Support - Doc Type: Task Memorandum
• Date: 11/5/2001
• DSS Category: Surface Water
• DSS: Colorado River
• Basin: Colorado Mainstem
• Contract/PO #: C153933, C154062
• Grant Type: Non-Reimbursable
• Bill Number: SB92-87, HB93-1273, SB94-029, HB95-1155, SB96-153, HB97-008
• Prepared By: Leonard Rice Engineering

Total Basin 87,449 79,649 9 % 86,215 1 %
Difference = (StateCU Results- StateMod Results)/StateCU Results
Wet-Year Crop Consumptive Use Comparison
Table 5 shows the total basin consumptive use estimates and the consumptive use estimates for
the explicit and aggregate structures for the representative wet year 1984. Focusing on explicit
structures, the current StateMod estimates consumptive use of explicit structures in wet years
that is much closer to the StateCU results than the CRDSS StateMod estimates. Although not as
intuitive as the dry year analysis, the wet year analysis recognizes that when more water is
available, efficiencies are generally lower and more of the diverted water returns to the river.
Therefore, there is more water for subsequent diversions and basin-wide consumptive use is
higher.
Table 5
Crop Consumptive Use Comparison Representative Wet Year - 1984
StateCU Previous CRDSS StateMod Enhanced StateMod
Comparison Results Results % Difference Results % Difference
Explicit Structures 41,862 40,381 4 % 41,139 1
A re ate Structures 20,249 23,967 -18 % 23,966 -18
Total Basin 62,111 64,348 -4 % 65,335 -5
Difference = (StateCU Results- StateMod Results)/StateCU Results
Conclusions
The following summarizes the main conclusions discussed during the Results Section:
• The Previous CRDSS analysis and the Enhanced analysis, using the variable efficiency
and soil moisture accounting options, result in streamgage, diversion, and reservoir
calibration that is considered good.
• Both simulations result in predicted streamflows, diversions, and reservoir end-of--month
contents that match gaged data well on both an annual and monthly basis.
• The Previous CRDSS analysis predicts streamflows during the representative dry-year
(1977) that average 2 percent higher than gaged streamflows, while the Enhanced
analysis predicts streamflows that average 6 percent lower than measured.
• The Previous CRDSS analysis predicts diversions during the representative dry-year
(1977) that average 3 percent lower than measured diversions, while the Enhanced
analysis predicts diversions that average 11 percent lower than measured. Most of the
shortages in the current analysis occur in Water District 54 on Slater Creek and Little
Snake River, where the four aggregate diversion structures are shorted by an average of
30 percent. These aggregate structures account for more than 50 percent of the demand
in this water district. Because the aggregate diversions are "estimated" based on average
efficiencies, the Previous CRDSS analysis, which used average efficiencies during
simulation, was more likely to meet those demands.
VariableEff Taskl-5 15 of 17 November 5, 2001