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

Instream Flow Recommendation(s)
BLM recommended an enlargement of 2.75 cfs during the summer, based on its October 7, 2005
and August 19, 2004 data collection efforts (see Appendix A). The modeling results from this
survey effort are within the confidence interval produced by the R2Cross model.
Land Status Review
Total Length Land Ownership
Upper Terminus Lower Terminus (miles) % Private % Public
Confluence with
Confluence with
Tarbell & 4
1 23 % 77
Chavez Creek .
Alexander Ditch
The 77% of public lands in this reach is comprised of 37% USFS lands and 40%BLM lands.
Biological Data
The BLM has conducted field surveys of the fishery resources in this stream and have found a
natural environment that can be preserved. As reported in the letter from BLM to the CWCB
"Pauline Creek is a moderate gradient stream with large substrate and good vegetative cover.
Fishery surveys indicate that the creek supports aself-sustaining brook trout, rainbow trout,
brown trout, and white sucker fishery. The stream environment is presently in good condition
and provides suitable substrate, channel stability, water quality, and food supplies for salmonids.
However, the stream has a high number of pools and beaver ponds, so spawning locations are
limited. Accordingly, it is important to provide stream flows to maintain the limited amount of
spawning habitat and to maintain water exchange in pools during low flow periods." (See Fish
Survey in Appendix B).
Field Survey Data
BLM staff used the R2Cross methodology to quantify the amount of water required to preserve
the natural environment to a reasonable degree. The R2Cross method requires that stream
discharge and channel profile data be collected in a riffle stream habitat type. Riffles are most
easily visualized as the stream habitat types that would dry up first should streamflow cease.
This type of hydraulic data collection consists of setting up a transect, surveying the stream
channel geometry, and measuring the stream discharge. Appendix B contains copies of field
data collected for this proposed segment.
Biological Flow Recommendation
The CWCB staff relied upon the biological expertise of the cooperating agencies to interpret
output from the R2Cross data collected to develop the initial, biologic instream flow
recommendation. This initial recommendation is designed to address the unique biologic
requirements of each stream without regard to water availability. Three instream flow hydraulic
parameters, average depth, percent wetted perimeter, and average velocity are used to develop
biologic instream flow recommendations. The CDOW has determined that by maintaining these
three hydraulic parameters at adequate levels across riffle habitat types, aquatic habitat in pools
and suns will also be maintained for most life stages of fish and aquatic invertebrates (Nehring
1979; Espegren 1996).
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