C150109 Feasibility Study

• Contract/PO #: C150109
• Contractor Name: Larimer and Weld Irrigation Company, The
• Contract Type: Loan
• Water District: 2
• County: Weld
• Bill Number: MC3
• Loan Projects - Doc Type: Feasibility Study

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to avoid any indication of intent to abandon any part of any water right. Beyond the protection
of direct flow rights, further design capacity considerations include possible additional Hows from
reservoir deliveries, upslope tailwater, precipitation runoff, and delivery scheduling allowances.
Application of a flow rate factor of 1.5, to the direct decreed flow rate, is usually sufficient to
provide conservative estimates for design discharge for water control structures.

An additional factor that has an influence on required hydraulic capacity of the canal is the carrier
function for water owned by shareholders. The most significant source of carried water is the
Colorado-Big Thompson (C-BT) Project. Approximately 95 shares of C-BT water, which have
typically accounted for 1/3 to 1/4 of annual deliveries; with daily carriage flow rates as high as
425 cfs in the past 10 years, are owned by ditch shareholders. Reservoir water from the big
Windsor Reservoir (delivered by exchange) has typically run from 1/4 to 1/3 of the amount ofC-
BT water on an annual basis. Non-direct flows from nine other sources have also augmented flow
in the canal at various times in the most recent 15 years of record examined incident to this report.

Total water delivered through the Larimer & Weld system average approximately 90,000 acre-feet
per year.

NEED FOR THE PROJECT

The Larimer & Weld Ditch (Eaton Ditch) is typical of main supply canals used for irrigation in
Colorado. The canal is checked at particular locations to raise the level of the water in the canal
to allow discharge through headgates into lateral ditches or directly onto fields. The existing
check structures for the Larimer & Weld Ditch are concrete structures that range from 25 feet in
width to 14 feet. The water is checked in the ditch at the check structures by inserting stoplogs
(boards) into guides in the structure. The stoplogs are generally 4 feet to 6 feet in length and the
ditch is typically check from one (1) to four ( 4) feet in height to push water out the headgates.

The check structures in Eaton Ditch have been in service since near the start of canal operations
in the late 1800's. Although various localized structural repairs or modifications had been done,
no canal control structures had been totally replaced until recently when five new automated
checks were constructed to replaced existing stoplog controlled structures. The new check
structures have automated, air operated gates that have demonstrated a significant potential for
canal operational imp~ovements. Based on their experience with these checks, the Larimer &
Weld Irrigation Company is planning to replace the remaining checks on the system with similar
structures. A photograph of one of the new checks constructed in 2001 is shown in Appendix A.

EXISTING FACILITIES

The check structures that are required for effective water control on the Larimer & Weld system
are listed on Table 1. Under the column labeled "Comment" is the action we believe is required
to maintain effective operation of the ditch.

Larimer & Weld Feasibility Study

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