9344

• UCREFRP Catalog Number: 9344
• Author: Camp Dresser & McKee Inc.
• Title: Replacement of the Plateau Creek Pipeline.
• USFW Year: 1996.
• USFW - Doc Type: Denver.
• Copyright Material: NO

Cameo call was on and Ute Water was full reliant u on re lacement reservoir and Je Creek
Y P P n'Y
~ releases for its supplies (see Attachment D -1977 and other years).
"" Attached are a series of graphs which depict the projected flow reductions at the top of the 15-mile
reach due to the District's operations in differing but meaningful ways. Figure 3.7 shows the
monthly reductions which would have occurred during the minimum runoff year on the Colorado
River during the study period (1977) and the maximum runoff year (1984). In 1977, reductions are
near average until the onset of the runoff season in April, when reductions dramatically drop off to
about zero by the last 4 months of the year. During this year, availability of the District's direct
diversion rights would have been limited, necessitating the release of water from the Jerry Creek
Reservoirs. Additionally, when water would have been available from the District's appropriations,
the Cameo call would have been on, resulting in replacement reservoir releases. These two factors
result in near-zero flow reductions in the Colorado River when compared to historical flows. In the
maximum runoff year (1984), water was in great supply and no replacement reservoir water was
required, resulting in larger overall flow reductions by the District. Thus, hydrologic effects. are
expected to be minor during drought conditions when flows are most critical to endangered fish.
Larger flow reductions, which may occur during wet years, should not represent as significant an
effect to endangered fish since river flows during such periods are generally plentiful.
Figure 3.8 shows what the annual variation would have been in flow reductions over the 19-year
simulation period. Reductions average about 26 cfs on an annual basis, but range from 13 cfs in
1977 to 30 cfs in 1975.
Figure 3.9 shows what flow reductions would have been over a representative low flow /high flow
cycle which occurred from 1976-1980. The bars represent the actual flow reductions simulated and
the line shows the average monthly reductions over the fu1119-year period. The graph demonstrates
that flow reductions will be significantly below average during drought periods when reliance on the
Jerry Creek Reservoirs and replacement reservoir releases is high, followed by higher than average
reductions when flows on the river recover, the Jerry Creek Reservoirs can be refilled, and no
_ replacement water is needed.
~' Figure 3.10 is a frequency distribution of the flow reductions that would have been caused by the
District's future operations. The graph shows the percent of time that flow reductions are above or
below the rates on the horizontal axis. The 50 percent frequency rate is 25.7 cfs; i.e., half the
reductions. are above 25.7 cfs and half are below. The relative steepness of the curve near the center
of the graph indicates that flow reductions tend to occur more often in the steep portion of the graph
(22-39 cfs) with relatively few occurrences outside of this range.
Figure 3.11 compares the average monthly adjusted historic flows to what the reduced flows on the
Colorado River at the top of the 15-mile reach would have been following District diversions.
Similarly, Figures 3.12 and 3.13 compare monthly historic and future flows for the low runoff (1977)
and high runoff (1984) years. The charts emphasizes that while flow reductions do occur, the effects
on the Colorado River are very small due to the large flows in the river.

CDM Camp Dresser & McKee
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