SouthPlatteComments11

• Basin: South Platte
• Title: Comments 11
• Date: 12/12/2003
• SWSI - Doc Type: Comments

maintenance projects, or certain water rights constraints, it may not be possible to meet
the guidelines~ Denver Water and Aurora will strive to limit streamflow fluctuations
below Spinney, Eleven Mile, and Cheesman reservoirs within the operational limits
described above. Particular emphasis will be placed on limiting fluctuations that could
adversely affect the various life stages of brown and rainbow trout Annual operating
plans described in Section E will reflect this emphasis~ Eleven Mile Reservoir when full
and spill provides damping of streamflow fluctuations.

Table 3: Outflow Ramping Schedule
Maximum Change per Hour - % of Existing Flow

Flow Range ( cfs)
0-50
51..100
101-200
201-400
401-600
601-800
>800

Eleven Mile
17
11
14.5
9.5
7
6
5

Cheesman
25
17
20
14
11
9
8

Roberts
Tunnel
17
15
19
12
10
9

c. Temperature Moderation

The opportunity to moderate stream temperature below a reservoir occurs when:
· water temperature varies with depth inside the reservoir, and
· water can be selectively withdrawn at various depths to blend temperature4
In reservoirs with only one outlet level, blending can only be done when the reservoir is
full and also discharging over the top of the dam (spilling).

CDOW recommends stream temperatures below dams be maintained between 500 and
600 F from June 1 through September 30t This temperature range enhances rainbow and
brown trout growth and physiology. Rainbow and brown trout growth are maximized at
temperatures ranging from 650 F to 680 F, but the incidence of physiological stress and
susceptibility to disease and parasitic infections increases at these higher temperatures.
Warmer water, greater than 600 F, may also enhance western white sucker hatching
success, growth and physiology while negatively impacting sportfish management
objectives. Maintaining colder temperatures during the summer and early fall period will
gi ve a margin of error during low streamflow periods and will hopefully extend the
cooling enhancement farther downstream~

The other temperature effect is the increase and decrease in stream temperature as the
reservoir spills and stops spilling~ Without time for acclimation, this can result in
temporary stress to the trout population. AltllOUgh trout appear able to survive short-term
temperature fluctuations of a couple of degrees (F) per hour, this may cause stress and
may interrupt behaviors, such as spawning. Therefore, temperature fluctuations

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