BOARD02095

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

Table 2: Data - Lower Reach

Party Date Q 250%-40% Summer (3/3) Winter (2/3)
BLM 4/29/1997 5.18 13.6 -2.2 2.4 0.9(1)
BLM 9/19/2001 1.43 0.6 - 3.6 1.5 1.4

ELM = Bureau of Land Management DOW = 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 upper reach summer flow recommendations, which meet 3 of 3 criteria and are within the
accuracy range of the R2CROSS model, range from 2.5 cfs to 1.2 cfs (See Table 1). Averaging
the three summer flow recommendations within range results in a 1.9 cfs summer
recommendation. The upper reach winter flow recommendations, which meet 2 of 3 criteria and
are within the accuracy range of the R2CROSS model range from 1.1 cfs to 1.0 cfs (See Table
1). Averaging the two winter flow recommendations within range results in a 1.0 cfs winter
recommendation. The lower reach summer flow recommendations, which meet 3 of 3 criteria
and are within the accuracy range of the R2CROSS model, range from 2.4 cfs to 1.5 cfs (See
Table 2). Averaging the two summer flow recommendations within range results in a 2.0 cfs
summer recommendation. 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 required.

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 hydro graph below was derived from data collected by the
USGS stream gage for Badger Creek near Howard, CO (ID #07093775), which has a drainage
area of 211 square miles (See Gage Summary in Appendix C). The total drainage area of the
Currant Creek Drainage upstream of Thirtyone Mile Creek is approximately 63.6 square miles,
the total drainage area of Currant Creek upstream of Mill Gulch is approximately 96.7 square
miles and the drainage area of Currant Creek upstream of Cottonwood Creek is approximately
146.7 square miles. The period of record for this gage was 1980-2001, the period of record used
by staff in their analysis was 1980-2001, or 21 years of record. Table 3 below displays the
estimated stream flow of Currant Creek, in terms of a percentage of exceedence.

Table 3: Estimated flow Currant Creek u/s of Thirty one Mile Creek.

Exceedences
1%
5%
10%
20%
50%
80%
90%
95%
99%

Januarv Februarv March ADril Mav June Julv Auaust SeDtember October November December
3.03 4.36 6.63 33.19 20.49 9.34 8.59 8.43 3.23 3.65 3.92 3.32
2.66 2.86 5.12 13.11 11.59 7.54 4.82 4.52 2.59 3.18 3.32 2.86
2.27 2.56 4.22 6.33 8.74 6.33 3.92 3.32 2.41 2.84 2.89 2.59
1.96 1.99 3.01 4.52 5.73 3.92 2.83 2.71 2.02 2.45 2.56 2.26
1.57 1.57 2.32 3.01 3.01 2.53 1.85 1.99 1.66 1.87 2.17 1.66
1.18 1.36 1.69 2.44 2.23 1.75 1.54 1.48 1.33 1.57 1.75 1.24
1.05 1.18 1.48 2.05 2.05 1.60 1.39 1.33 1.21 1.45 1.60 0.99
0.96 1.05 1.36 1.87 1.93 1.54 1.33 1.18 1.02 1.39 1.51 0.90
0.63 0.45 1.21 1.55 1.73 1.39 1.21 0.87 0.22 0.57 1.21 0.69

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