PROJ00505

• Contract/PO #: C153419
• Contractor Name: San Miguel Water Conservancy District
• Water District: 0
• County: San Miguel
• Bill Number: XB 99-999
• Loan Projects - Doc Type: Feasibility Study

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while the sum of daily peaks remains less than the ditch capacity. A small

storage reservoir of 200 to 400 acre-feet could effectively manage this diurnal

fluctuation and allow for a maximum 24-hour diversion through the Naturita

Canal. A sophisticated management plan plus a willin~ness to operate the

system at inconvenient hours would be required to achieve the maximum benefit.

Some portion of the project yield may come early in the runoff season before

diversion facilities are accessible because of deep snow. The details of an

operation plan to maximize yield should be explored in a study which also

examines the potential regulating storage sites.

Assuming the project supply to be available to the Cone Enlargement via

the Naturita Canal, a 10-year operation of the Cone Reservoir was performed for

the period 1974-1983, (a graph of the reservoir operation is shown in Figure

4-6 (a)). The enlarged reservoir (total capacity of 5,800 acre-feet) would

have filled in 6 of the 10 years. An annual average of 5,705 acre-feet of

supplemental irrigation could be provided, on the basis of need, within the

Gurley and Cone service areas. Over 950 acre-feet could have been provided in

1977, the dryest year studied, without benefit of hold-over storage from the

previous year. The maximum supplemental benefit would have occurred in 1980

with a total supply of 10,079 acre-feet. The entire operation study has been

included in Appendix C.

Need in the two irrigation service areas was determined by comparing

historic supply with an ideal demand. Supplemental water was provided up to

the ideal demand when available. Additional storage in the reservoir

enlargement allowed for releases of supplemental water later in the irrigation

season. In very dry years, the additional storage had a limited effect due to

a lack of water to fill.

A graph comparing the historic and the project irrigation supplies is

shown as Figure 4-6 (b). A complete historic diversion record was not

available for Gurley and Cone Reservoir as noted on the graph. It is apparent

from the graph that an enhanced water supply coupled with an enlarged reservoir

provides benefits in every year. It was assumed that the water provided by the

project could be used in either of the Cone or Gurley service areas via

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