ISFAPPC04482 ‎(2)‎

• Case Number: 03CW0040
• Stream Name: La Garita Creek
• Watershed: Closed Basin
• Water Division: 3
• Water District: 27
• County: Saguache
• Instream Flow App - Doc Type: Supplemental Data

Biological Data

The Division of Wildlife has conducted surveys of the fishery resources on this stream and have
found a natural environment that can be preserved. As reported for this reach of stream in the
BLM letter to the CWCB " The existence of a natural environment and cold water salmonid
fishery was established in Case No 3-76W3645. For reference we have. attached a fishery
survey from the Division of Wildlife, which profiles the brown trout fishery" (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 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 CD OW 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, 5 data sets were 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 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 8/2312001 9.48 23.7 -3.8 3.1 tl) 2.7U)
BLM 5/3012002 3.08 7.7 - 1.2 5.4 1.0t!)
BLM 5/3012002 3.19 8.0 - 1.3 3.6 0.6P)
BLM 8/0812002 1.73 4.3 -0.7 2.5 2.5
BLM 8/08/2002 1.95 4.9 - 0.8 2.4 1.7

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

Biologic Flow Recommendation
The summer flow recommendations, which met 3 of 3 criteria and are within the accuracy range
of the R2CROSS model range from 5.4 cfs to 2.4 cfs (See Table 1). The winter flow
recommendations, which met 2 of 3 criteria and are within the accuracy range of the R2CROSS
model range from 2.5 cfs to 1.7 cfs (See Table 1). Averaging the four summer flow
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