WSP11269

• File Number: 8142.100
• Description: Trinidad Project - Studies - Operation Studies
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 1/1/1996
• Author: CWCB
• Title: Trinidad Background Info Notebook Part 5
• Water Supply Pro - Doc Type: Report/Study

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9. Headgate Irri 9at ion Requi rement. - When a computed headgate i rriga-
tion requirement was used for analysis it was based on the Lowry-Johnson {Lowry
and Johnson - April 1941. Consumptive Use of Water for Agriculture, Proc.
A.S.C.E. (pp. 595-616)) method for crop consumptive use. Also, a farm loss
of 30 percent of farm delivery and a transportation loss of 30 percent of the
head9ate i rri gat i on requ i rement was assumed. Th is was the same as that used
in the 1961 Study.

IV. EVALUATION OF PROJECT OPERATION

During the first few months of the review of the operating principles,
discussions were held with the States of Kansas and Colorado to identify the
issues that needed investigation. From these discussions, the initial thrust of
the study focused on the following topics:

1. Is the transfer of water stored under the Model right to the joint use pool
at the end of the irrigation season consistent with the operating principles
and, if not, I/hat effect does it have on downstream water users?

2. Is the storage of water during the nonirrigation season under the priorities
of the direct flow rights of the project ditches consistent with the operating
principles and, if not, what effect does it have on downstream water users?

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3. Was the temporary storage of inflow below the bottom of the flood control
capacity for flood control purposes consistent with the operating principles and
Kansas Condition No. 1 and was the release of this water carried out in a manner
such that the water supply available to downstream users was not reduced?

4. Were the exchanges of transmountain water from the mainstream of the Arkansas
River into Trinidad Reservoir consistent with the operating principles and were
the exchanges carri ed out in a manner that di d not reduce the water supp 1y
available to downstream water users?

5. Did the total area of lands irrigated by the project exceed the maximum per-
mitted by the operating principles?

6. Were headgate diversions by project ditches consistent with the operating
principles?

An initial draft of the report was released to the interested parties on
December 20, 1985 _ Thi s draft report and its append ices documented the data,
analysis and conclusions reached during the investigations performed in 1985.
The investigations dealt predominantly with the six topics mentioned above and
thei r impacts during the years of the review period (1979-1984). The impacts
were presented in terms of changes of storages and flow in the project area,
but were not translated to impacts to the inflow to John Martin Reservoir. ,

The project 1 ands that were i rri gated duri ng the revi ew per i od were substan-
tially reduced because the irrigation facilities serving the model land were
being rehabilitated. Therefore, the conditions and impacts experienced are not
considered to be representative of those that would occur when all project lands
are being irrigated.

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The i nit i a 1 draft report drew extens i ve comments from both the States of Kansas'., il.1
and Colorado (significant letters of comment are contained in Appendix V), ,,;,i

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