BOARD01016

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

Biologic Flow Recommendation
The summer flow recommendations, which meet 3 of3 criteria and are within the accuracy range
of the R2CROSS model range from 1.6 cfs and 1.5 cfs (See Table 1). Averaging the summer
flow recommendations within range results in a 1.6 cfs summer recommendation. The winter
flow recommendation, which meets 2 of 3 criteria and is within the accuracy range of the
R2CROSS model is 0.9 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 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 hydrograph below was derived from data collected by the
USGS stream gage for East Fork Arkansas River near Leadville, CO (ID #07079300), which has
a drainage area of 50 square miles (See Gage Summary in Appendix C). The total drainage area
of the Birdseye Gulch Drainage is approximately 5.2 square miles. The period of record for this
gage was 1913-1924, the period of record used by staff in their analysis was 1913-1924, or 11
years of record. Table 2 below displays the estimated stream flow of Birdseye Gulch, in terms of
a percentage of exceedence.

Table 2: Estimated flow Birdseye Gulch.

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

January February March April May June July Auaust September October November December
1.46 1.14 1.35 3.12 39.28 67.60 18.97 10.88 7.97 4.26 4.90 1.46
1.46 1.14 1.35 3.12 28.29 43.16 15.50 9.15 5.30 2.91 2.39 1.46
1.04 1.04 1.04 1.98 20.04 35.15 13.29 7.80 4.26 2.91 2.39 1.14
1.04 1.04 1.04 1.66 14.56 28.50 11.71 5.84 3.33 2.81 1.56 1.04
0.83 0.83 0.83 1.04 5.62 19.86 7.49 3.33 2.08 1.66 1.04 1.04
0.52 0.62 0.73 0.83 2.72 10.82 4.99 2.18 1.46 1.04 0.62 0.83
0.52 0.52 0.52 0.73 1.25 9.57 4.06 1.66 1.25 0.62 0.62 0.52
0.42 0.52 0.52 0.62 1.14 8.32 3.39 1.35 0.83 0.52 0.52 0.52
0.42 0.52 0.52 0.62 1.14 4.53 2.39 1.25 0.52 0.42 0.52 0.52

Birdseye Gulch Estimated Stream Flow

3
2.5
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$ 1.5
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0.5
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