1-02CW373 Supplemental Data

• Case Number: 02CW0373
• Stream Name: South Fork South Platte River
• Watershed: South Platte
• Water Division: 1
• Water District: 23
• County: Park
• Instream Flow App - Doc Type: Supplemental Data

Land Status Review
Upper Terminus
Lower Terminus
Total Length
(miles)
Land Ownership
% Private
% Public
U.S. Highway 285
East Section Line
S24 T12S R77W 6PM
6.7
33%
66%
This segment is approximately 66% public land and 33% private land. 100% of the public land
is managed by the CDOW (See attached Figure 1).
Biological Data
The CDOW has conducted field 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 CDOW'S
recommendation letter to the CWCB, "Fishery surveys indicate that the stream environment
supports a has a very healthy trout population (See CDOW Fish Survey in Appendix B).
Field Survey Data
CDOW 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 of field 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 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 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.
4