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• Board Meeting Date: 11/18/2007
• Description: ISF Section - Uncontested 2007 Instream Flow Appropriations
• Board Meetings - Doc Type: Memo

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• Moving through the channel the seasonally deposited sediment that can clog
salmonid spawning zones;
• Removing the algae that deposits on the stream bed and, over time, "cements"
sediment particles into place;
• Recharging alluvial aquifers that release water slowly during low flow periods;
• Maintaining riffle habitat by clearing collections of debris and bed material
deposits that effectively dam channels;
• Providing the cues to species that initiate spring spawning;
• Creating the disturbed areas necessary for riparian plant species germination to
maintain both age and species diversity.
The morphology of Pauline Creek would accentuate the effects of protecting a year-round
flow of 3.5 cfs. As a moderate to low gradient stream, Pauline Creek requires adequate
average velocities to suspend and transport sediment. Furthermore, 3.5 cfs does not
generally provide the velocity preferred by salmonids during the high growth summer
months. Pauline Creek is also limited in the amount of habitat suitable for spawning
because of the prevalence of pools in this system. Since spawning habitat is limited by
stream morphology, a further limitation due to a lack of the velocities preferred for
spawning will likely result in future declines in fish populations. BLM believes the
current diverse and productive fishery is the result of the current flow regime that is
consistently above the current 3.5 cfs instream flow water right.
Finally, the morphology of Pauline Creek has produced other biological characteristics
that would accentuate the effects of protecting ayear-round flow rate of 3.5 cfs. Pauline
Creek's abundant pools have resulted in much open water habitat and limited vegetative
cover. BLM is not concerned that increased stream temperatures due to solar radiation
will result in direct mortality to fish. Rather, BLM is concerned that, with inadequate
water exchange through those pools, water temperatures will likely rise and dissolved
oxygen will likely decline These changes in water temperature and oxygen saturation
could significantly change the composition of the aquatic macroinvertebrate community
which would be detrimental to salmonids. Maintaining a healthy salmonid community is
BLM's management objective for this creek.
Pauline Creek has become a significant wetlands asset in the Cochetopa Creek watershed
because of grazing management changes during the last 25 years. In many locations,
Pauline Creek contains wetlands and riparian vegetation across the entire valley floor.
These extensive wetland communities are the consequence of the high snowmelt runoff
that is captured and stored in groundwater and side channels. BLM would expect a
significant decrease in wetland acreage if flows were held to the 3.5 cfs rate year-round.
If Pauline Creek were maintained at the current year-round 3.5 cfs flow rate, the
functions listed above would be severely impaired. BLM recognizes CWCB instream
flow water rights are not designed to protect all of the peak flow, just the flows necessary
to protect the environment to a reasonable degree. This increase will allow this objective
to be achieved without excessively limiting the water available for appropriation. A 6.25