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<br />Biologic Flow Recommendation
<br />The summer flow recommendations, which meet 3 of 3 criteria and are within the accuracy range
<br />of the R2CROSS model range from 2.8 cfs to 1.7 cfs (See Table 1). Averaging the two summer
<br />recommendations within range results in a 2.25 summer recommendation. The winter flow
<br />recommendations, which meet 2 of 3 criteria and are within the accuracy range of the R2CROSS
<br />model range from 2.0 cfs and 0.9 cfs (See Table 1). Averaging the two winter recommendations
<br />within range results in a 1.45 winter recommendation. It is our belief that recommendations that
<br />fall outside of the accuracy range of the model, over 250% of the measured discharge or under
<br />40% of the measured discharge may not give an accurate estimate of the necessary instream flow
<br />required.
<br />
<br />Hydrologic Data
<br />
<br />After receiving the cooperating agency's biologic recommendation, the CWCB staff conducted
<br />an evaluation of the stream hydrology to determine if water was physically available for an
<br />in stream flow appropriation. The hydrograph below was derived from data collected by the
<br />USGS stream gage for Poncha Creek at Poncha, CO (ID #07093000), which has a drainage area
<br />of 56 square miles (See Gage Summary in Appendix C). The total drainage area of the Little
<br />Cochetopa Creek Drainage upstream of Spruce Creek is approximately 13.5 square miles. The
<br />period of record for this gage was 1911-1918, the period of record used by staff in their analysis
<br />was 1911-1918, or 7 years of record. Table 2 below displays the estimated stream flow of Little
<br />Cochetopa Creek, in terms of a percentage of exceedence.
<br />
<br />Table 2: Estimated flow Little Cochetopa Creek,
<br />
<br />Estimated LiUle Cochetopa Creek Streamflow
<br />Exceedences
<br />1%
<br />5%
<br />10%
<br />20%
<br />50%
<br />80%
<br />90%
<br />95%
<br />99%
<br />
<br />Januarv Februarv March ADrll Mav June Julv Auaust Seatember October November December
<br />3,14 3,62 4,82 17,45 60,27 48,21 30,86 13.42 8.32 9,16 6.44 3,38
<br />2.41 2.41 3,86 13,02 46.55 41.46 26,04 10,16 5,30 7,96 5,30 2,89
<br />2,17 2.17 3,18 8,92 36.88 35.44 19,82 8,92 4,82 5.45 3,86 2,72
<br />1.93 2,03 2,65 6,27 31,58 31,34 11,14 6,03 3,13 3,13 2,65 2.41
<br />1,69 1,69 1,93 4,58 17,84 20,01 6,27 3,86 2.17 1,93 1,69 1,69
<br />0,72 0,96 0,72 2,89 9,64 13,50 4,82 2,65 1.45 1.45 0,96 0,84
<br />0.48 0.48 0,72 2,17 5,79 10,37 3,86 2,17 1.45 1.21 0,96 0,72
<br />0.48 0.48 0.48 1,93 4,82 8.44 3,62 1,69 1,16 0,96 0,96 0,60
<br />0.48 0.48 0,24 0,87 4,34 6,53 3,13 1,33 0,84 0.76 0,60 0.36
<br />
<br />Little Cochetopa Creek Estimated Stream Flow
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