BOARD02186

• Board Meeting Date: 1/27/2004
• Description: ISF Section - Instream Flow Appropriations - Dyke Creek
• Board Meetings - Doc Type: Memo

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 USFS 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, 3 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. As indicated in the table only one of the cross sections meet the

Table 1: Data
Party X-see

Date Q

Z50%-40%

1.125 - .18

Slimmer
3/3
3.03

Winter (2/3)

USFS # 1

6/18/2003 .45 cfs

. 1

USPS #3

6/18/2003 1.36 cfs

3.4 - .544

4.5

3.6

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

Biologic Flow Recommendation
The spring/summer flow recommendation, which meets 3 of 3 criteria (x-section 2 and 3), and is
within the accuracy range of the R2CROSS model, is 3.2 cfs (See Table 1). The winter flow
recommendation, which meets 2 of 3 criteria (x-section 1 and 2), and is within the accuracy
range of the R2CROSS model, is 1.0 cfs (See 'table 1). 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 art accurate 'estimate of the necessary
instream flow required.

Hydrologic Data
After receiving the cooperating agehcy'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 West Hubbard Creek neat I'aonia, CO (ID #09132900), which has a
drainage area of 2.4 square miles (See Gage Summl\ry in Appendix C). The total drainage area
of the Dyke Creek Drainage is approximately 4.7 square miles. The period of record for this
gage was 1955-1965, the period of record used by staff in their analysis was 1960-1973, or 13

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