Spring Creek Appendices

• Case Number: 05CW0245
• Stream Name: Spring Creek
• Watershed: North Fork Gunnison River
• Water Division: 4
• Water District: 40
• County: Gunnison
• Instream Flow App - Doc Type: Supplemental Data

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Field Survey Data

CD OW and CWCB 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 offield data collected for this proposed segment.

Biological Flow Recommendations

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, one data set was collected with the results shown in Table I below.
Table I 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 I: Data
Party
DOW/CWCB

Date
07/24/0 I

Q
6.3

250%-40%
15.8 - 2.5

Summer (3/3)
2.7

Winter (2/3)
0.8(1)

BLM Bureau of umd Management DOW Division of Wildlife
(1) Predicted flow outside of the accuracy range of Manning's Equation.

eweB Colorado Water Conservation Board
? = Criteria never met in R2CROSS Staging Table.

Biologic Flow Recommendations
On July 24, 2001 CD OW and CWCB personnel collected stream cross section information on
Spring Creek. The cross section information was processed using the R2CROSS program. The
Division's initial biologically-based instream recommendations are 0.8 cfs during the winter low
flow period and 2.7 cfs during the summer high flow period. 0.8 cfs meets two of the three
hydraulic criteria used to develop instream flow recommendations using R2CROSS (Espegren
1996). Similarly and also consistent with Espegren (1996), 2.7 cfs is needed to meet all three
hydraulic criteria. 0.8 cfs falls outside the range of accuracy for the R2CROSS model's estimate
for the roughness coefficient, Manning's "n" but we believe that 0.8 cfs will preserve the natural
environment to a reasonable degree and that no additional field investigations are necessary.

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Staff reviewed the data collected by the CDOW. The summer flow recommendation, which
meets 3 of 3 criteria and is within the accuracy range of the R2CROSS model is 2.7 cfs. The
winter flow recommendation which meets 2 of 3 criteria falls outside of the accuracy range of
the R2CROSS model is 0.8 cfs (See Table I). It is our belief that recommendations that fall
outside of the accuracy range of the model, over 250% of the measured discharge or under 40%
of the measured discharge may not give an accurate estimate of the necessary instream flow