ISFAPPC01558

• Case Number: 05CW0052
• Stream Name: Minnie Gulch
• Water Division: 7
• Water District: 30
• County: San Juan
• Instream Flow App - Doc Type: Supplemental Data

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Biologic Flow Recommendation
The summer flow recommendation, which meets 3 of 3 criteria and is within the accuracy range
of the R2CROSS model is 1.7 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 discnarge, 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 Animas River at Howardsville, Colorado (ID #09357500), which has a
drainage area of 55.90 square miles (See Gage Summary in Appendix C). The total drainage
area of Minnie Gulch is approximately 4.9 square miles. The period of record for this gage was
1935 to 1982, the period ofrecord used by staff in their analysis was 1935 - 1982, or 47 years of
record. Table 2 below displays the estimated flow of Minnie Gulch at the gage, in terms of a
percentage of exceedence.

Table 2: Estimated Average Stream Flow on Minnie Gulch
Exceedences Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nav Dee Year
1% 2.2 1'.9 2.9 19.5 62.1 92.3 66.0 23.9 19.1 13.3 5.5 2.8 64.4
5% 1.9 1.8 1.9 12.7 49.1 71.4 49.6 13.9 11.6 7.3 3.8 2.4 41.8
10% 1.8 1.8 1.8 9.0 43.3 64.8 40.1 11.6 8.6 5.8 3.4 2.1 27.9
20% 1.7 1,.6 1.6 6.4 34.5 55.2 28.6 9.5 5.7 4.3 2.9 1.9 12.5
50% 1.4 1.3 1.3 2.6 19.4 37.0 14.0 5.5 3.4 2.6 1.9 1.6 2.6
80% 1.2 1.1 1.1 1.6 9.0 22.6 7.6 3.6 2.6 1.9 1.5 1.3 1.4
90% 1.1 1.1 1.0 1.3 6.3 18.3 5.5 3.0 2.3 1.7 1.4 1.2 1.2
95% 1.1 1.0 1.0 1.1 4.7 16.0 4.3 2.7 2.0 1.6 1.3 1.1 1.1
99% 0.9 0.9 0.9 1.0 2.1 10.0 3.3 2.2 1.7 1.3 1.1 1.0 1.0

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