BOARD00048 ‎(2)‎

• Board Meeting Date: 9/19/2006
• Description: ISF Section - Contested Instream Flow Appropriation Hearing - Elkhead and Armstrong Creeks
• Board Meetings - Doc Type: Hearings

the long-term persistence of each species. The success of such plans could potentially curtail the .
need for federal listing of these species under the Endangered Species Act (ESA). These species
are not currently federally listed" (See CDOW Fish Survey in Appendix B).

Field Survey Data

CDOW 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).

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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, 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% ofQ), 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)
DOW 07/26/2005 0.42 1.0-0.2 1.0 0.4

DOW = Division of Wildlife

Biologic Flow Recommendation _
The summer flow recommendation, which met 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 met 2 of
3 criteria and is within the accuracy range of the R2CROSS model range is 0.4 cfs (See Table 1).

Hydrologic Data
After receiving the cooperating agency's biologic recommendation, the CWCB staff conducted
an evaluation of the stream hydrology to determine if water was physically available for an
instream flow appropriation. The hydrograph below was derived from data collected by the
USGS stream gage for Elkhead Creek near Clark, CO (#09244500), which has a drainage area of

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