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<br />Biologic Flow Recommendation
<br />The summer flow recommendation, which meets 3 of 3 criteria and is within the accuracy range
<br />of the R2CROSS model is 4.2 cfs (See Table 1). The winter flow recommendation, which meets
<br />2 of 3 criteria and is within the accuracy range of the R2CROSS model is 2.9 cfs (See Table I).
<br />It is our belief that recommendations that fall outside of the accuracy range of the model, over
<br />250% of the measured discharge or under 40% of the measured discharge may not give an
<br />accurate estimate of the necessary instream flow 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 />instream flow appropriation. The hydrograph below was derived from data collected by the
<br />USGS stream gage for Halfinoon Creek near Malta, CO (ill #07083000), which has a drainage
<br />area of 23.6 square miles (See Gage Summary in Appendix C). The total drainage area of the
<br />Wildcat Gulch Drainage is approximately 3.8 square miles. The period of record for this gage
<br />was 1946-1998, the period of record used by staff in their analysis was 1946-1998, or 52 years of
<br />record. Table 2 below displays the estimated stream flow of Wildcat Gulch, in terms of a
<br />percentage of exceedence.
<br />
<br />Table 2: Estimated flow Wildcat Gulch.
<br />
<br />Exceedences
<br />1%
<br />5%
<br />10%
<br />20%
<br />50%
<br />80%
<br />90%
<br />95%
<br />99%
<br />
<br />January February March April May June July August September ctober ovem er ecem er
<br />1.45 1,29 1,77 4.19 25,75 47,18 47,66 21.58 8.Q7 4,19 3,06 1,61
<br />1.11 1.00 1,13 2.58 19,00 38.64 31,95 13,20 5.47 3,22 2.09 1.42
<br />0,90 0.84 0,97 2.09 14,65 33.81 26,08 9,93 4,67 2.90 1.77 1,22
<br />0,81 0.72 0,72 1,38 11,27 28.82 19,00 7.41 3,86 2.25 1.48 1,03
<br />0,61 0,56 0,56 0,90 5,96 19,00 11,27 4.83 2,58 1.61 1,11 0,77
<br />0.48 0.43 0.42 0,56 2,25 12,72 6,76 3.22 1,93 1.21 0,87 0,63
<br />0.40 0,38 0,37 0.43 1,48 10,31 5.15 2,74 1,61 1,08 0,79 0.56
<br />0,34 0,32 0.24 0.39 1.11 8,69 4.19 2.42 1.42 0,98 0,71 0.52
<br />0.24 0.27 0.19 0.27 0.79 5,57 3,08 1,93 1.13 0,82 0,55 0.43
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<br />Wildcat Gulch Estimated Stream Flow
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<br />4
<br />3
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