ISFAPPC01442 ‎(2)‎

• Case Number: 04CW0087
• Stream Name: Thirtyone Mile Creek
• Water Division: 2
• Water District: 12
• County: Park
• Instream Flow App - Doc Type: Supplemental Data

"The stream environment alars to be in stable condition and is imlving in some locations as
a result of recently changed grazing practices. Substrate, water quality, channel stability, and
food supplies are good for salmonids. However, bank stability and lack of cover are limiting
conditions and can create high stream temperatures. Accordingly, maintaining adequate flow is
important in preventing late summer fish kills. Fish surveys indicate that the reach supports a
self-sustaining population of brook trout, long-nose dace, and white suckers" (See BLM 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 in stream 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 maintaining these
three hydraulic parameters at adequate levels across riffle habitat types, aquatic habitat in pools
and runs will also be maintained for most life stages of fish and aquatic invertebrates (Nehring
1979; Espegren 1996).

For this segment of stream, one data set was collected with the results shown in Table 1 below.
Table 1 shows who collected the data (Party), the date the data was collected (Date), the
measured discharge at the time of the survey (Q), the accuracy range of the predicted flows
based on Manning's Equation (240% and 40% of Q), the summer flow recommendation based
on meeting 3 of 3 hydraulic criteria and the winter flow recommendation based upon 2 of 3
hydraulic criteria.

Table 1: Data

Party Date Q 250%-40% Summer (3/3) Winter (2/3)
BLM 4/29/1997 0.84 2.1 - 0.3 1.0 0.35

BLM = Bureau of Land Management DOW= Division of Wildlife
(1) Predicted flow outside of the accuracy range of Manning's Equation, ? = Criteria never met in R2CROSS Staging Table,

Biologic Flow Recommendation
The summer flow recommendation, which meets 3 of 3 criteria and is within the accuracy range
of the R2CROSS model is 1.0 cfs (See Table 1). The winter flow recommendation, which meets
2 of3 criteria and is within the accuracy range of the R2CROSS model is 0.35 cfs (See Table 1).

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