WSPC128

• File Number: 8240.200.39.L
• Description: Colorado River Threatened-Endangered - RIPRAP - CFOPS - General Reports-Maps-Data-Etc
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 8/31/1999
• Author: Unknown
• Title: Revised Discussion Paper - Accounting for Consumptive Uses Under the Programmatic Biological Opinion - Colorado River Mainstem - 08-31-99
• Water Supply Pro - Doc Type: Report/Study

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be added to the Recovery Action Plan according to standard procedures,
outlined in that plan. .if the Recovery Program is unable to complete those
elements which the Service has determined to be required for the second 60,000
acre-feet/year, consultation on projects with a Federal nexus may be reinitiated
in accordance with Endangered Species Act regulations and this opinion's
reinitiation requirements. "

2) Annually, the Service and the State will jointly collect consumptive use data and other
data necessary to update either the states CRDSS Consumptive Use Model or the states
CRDSS Colorado River Mainstem Water Right Planning Model Cl run. Data collected
would include irrigated acres (perhaps updated only every 5-years so that costs can be
shared with Reclamation's CU&L report), climatic data needed to run the "Modified
Blaney-Criddle" consumptive use model, as well as data on evaporation, municipal and
industrial uses, and other consumptive uses identified in Bureau of Reclamation's
consumptive uses and losses report. If the C I model run is used, this would include
updated demand data for "back casting" purposes.
3) Annually, or at a predetermined time interval like every 5-years, run the consumptive use
model or updated Clmodel and develop a consumptive use and losses report. This report
would verify that total consumptive uses have not increased on average by more than the
appropriate trigger amount (60,000 or 120,000 acre-feet) over the 1975-1995 base period.
4) In order to avoid potential problems associated with annual fluctuations do to variable
climatic factors, as well as model and data changes, all determinations of increases in
consumptive use will be made using the long-term averages since 1975. Assuming the
CRDSS Colorado River Mainstem Water Right Planning Model is used, two model runs
will be required. First, Cl for the entire updated study period (e.g. 1975 to year (n)) at
1995 demand levels will be required. Second, a new CI (call it C2) for the same updated
time period using year (n) demand levels "backcasted" over the period is required.
Comparing the difference between the long-term averages of the two model will identify . \
the increase in consumptive use over that time period. Model calibration and verification t.. f.fJ.4r r-e.Vft~t:P}
will be done with each update. There are no "CAP" amounts identified in this process,
the trigger is whether or not the difference between the two model runs exceeds either
the 60,000 acre-foot or 120,000 acre-foot trigger.
5) The report will be prepared on a water year basis. The report will document any changes
made to the model such as updated demand information.
6) The report will be completed by July I st of each year if done annually or within 6-months
of the close of a more infrequent reporting period.
7) This process as currently envisioned has the potential to become labor intensive
depending on the number of model changes and degree of "backcasting" involved. Costs
or appropriate cost-share arrangements will be worked out during the development of the
Recovery Programs annual work plan. Furthermore, because of cost considerations, the
process identified above is subject to change with the agreement of the program
participants through the current management process.

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