PROJ00040

• Contract/PO #: C153446
• Contractor Name: Grand Mesa Water Conservancy District
• Contract Type: Grant
• Water District: 0
• County: Delta
• Bill Number: XB 99-999
• Loan Projects - Doc Type: Feasibility Study

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The seasonal water supply in the Tongue Creek basin is a function of the
snowmelt runoff and runoff from rainfall. The runoff during the snowmelt
months of April, May and June constitutes approximately 70 percent of the
annual runoff. This fact enables forecasting of seasonal streamflow using
snow survey data with a high degree of reliability.

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The reservoir release rate is a function of the size of area to be irrigated,
minimum crop water requirement and available water supply in the stream.
Since low flow years can be predicted with a high degree of certainty and the
reservoir content is known, reservoir releases can be scheduled well in
advance before the start of the irrigation season. The success of such a
project operation depends on an efficient streamflow monitoring and fore-
casting system.

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6. The System's Operation Mode

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The schematic diagram on Figure IV-l demonstrates how the system might
work under the above operational considerations and configurations. Gen-
erally, direct flow water would be used in the upper basin first and in a
pattern based on priority by elevation. Existing storage in the upper part of
the study area would be used to supplement late season stream flows for the
upper basin's use. Cactus Park reservoir would store excess stream flows and
provide late season releases for the lower basin.

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If the system is to be successful, all irrigators would adopt a diversion
pattern equivalent to the minimum diversion requirement. In addition, most
of the water rights holders in the study area would have to be willing to
participate in the project. The following mode of operation would then be
utilized:

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All water rights holders would divert water in the minimum
diversion requirement pattern rather than at the decreed rates.
This would increase the water available for other direct flow
diversions, resulting in exchanges between the more senior and
more junior water rights.

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V-IO