Stream: West Fork SF of Slater Creek ‎(Upper Segement)‎ Executive Summary

• Description: Stream: West Fork SF of Slater Creek ‎(Upper Segement)‎ Executive Summary
• State: CO
• Water Division: 6
• Title: Stream: West Fork SF of Slater Creek ‎(Upper Segement)‎ Executive Summary
• Water Supply Pro - Doc Type: Report/Study

Biological Data
In July and September of 2009 TU and CDOW collected stream cross sectional data, natural
environment data, and other data needed to quantify instream flow needs. Previously survey data
collected by CROW indicated the stream supports healthy populations of Colorado River
cutthroat trout.
Field Survey Data
TU and CROW 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.
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 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, two 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'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
CDOW/TU
7/7/2009
14.5
36.1 —5.8
6.9
Out of range
CDOW/TU
9/17/2009
1.0
12.7-2.0
2.9
2.5
The summer flow recommendation, which meets 3 of 3 criteria and is within the accuracy range
of the R2CROSS model is 4.9 cfs. This recommendation was derived by averaging the results of
the two data sets. The winter flow recommendation, which meets 2 or 3 criteria and is within the
accuracy range of the R2Cross model is 2.5 cfs. The late summer recommendation of 3.5 cfs
was lowered due to water availability constraints.
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