PROJ00137

• Contract/PO #: C153467
• Contractor Name: Greeley, City of
• Contract Type: Loan
• Water District: 0
• County: Weld
• Bill Number: XB 99-999
• Loan Projects - Doc Type: Feasibility Study

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This compares with the 1,928 acre-feet per year available, if the dam is
enlarged. The added increment of firm yield is 153 acre-feet.

At Peterson Lake Reservoir, the 1,183 acre-feet of active storage is
sufficient to produce a firm yield of 1,014 acre-feet, as shown on Table
IV.10. A yi el d of 1; 181 acre-feet annually was developed for the reservoi r;
enl arged by 460 acre-feet. The incremental yi el d resulti ng from the
enlargement is 167 acre- feet.

The hi gh mountai n reservoi rs owned by the Ci ty are currently operated to
maximize deliveries of water to the North Poudre Irrigation Company in
exchange for CBT suppl ies and to provi de adequate water suppl i es duri ng the
winter months to the Bellvue Filtration Plant. This arrangement allows
delivery of CBT water to either the Cache la Poudre or Big Thompson Rivers. A
five percent shrink charge is assessed the City to account for river losses in
the exchange. When CBT water is treated at the Bellvue Plant, no additional
shrink charges are assessed. However, deliverfes to the Boyd lake Plants are
diverted via the Greeley - Loveland Irrigation Company Canal, and result in a
shrink charge of 22 percent to account for canal and system losses.

5.0 SEDIMENT

Sediment yield in the drainage basin above Twin Lakes was estimated from a
1974 sediment yield map published by the Colorado Land Use Corrrnission. Much
of the quantitati ve data on the map was based on i nformati on deri ved from
small dry reservoirs with drainage basins of one to five square miles. The
amounts of sediment refl ect the average wei ght and vol ume of sediment as
ordinarily deposited in these reservoirs. The information presented represents
an average yield over a period of time greater than 25 years.

The estimated sediment yield for the drainage basin above Twin lakes Reservoir
is shown to be very low compared wi th other drai nages in Colorado, and
averages less than 0.1 acre-foot per square mfle per year. The basin is a
high mountain area, with dense vegetative cover, and with resistant rock
outcrops; Assuming a 100-year project life, the total expected sediment yield
from the watershed is 9 acre-feet.

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