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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 2.1 cfs (See Table 1). The winter flow recommendation, which meets 2 of3 criteria and is within the accuracy range of the R2CROSS model is 1.5 cfs (See Table 1). 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 Halfmoon Creek near Malta, CO (ID #07083000), which has a drainage area of 23.6 square miles (See Gage Summary in Appendix C). The total drainage area of the Tunnel Gulch Drainage is approximately 3.1 square miles. The period of record for this gage was 1946-1998, the period of record used by staff in their analysis was 1946-1998, or 52 years of record. Table 2 below displays the estimated stream flow of Tunnel Gulch, in terms of a percentage of exceedence. Table 2: Estimated flow Tunnel Gulch. Exceedences 1% 5% 10% 20% 50% 80% 90% 95% 99% January February March Aoril May June July AUllust September October November December 1.18 1.05 1.44 3.42 21.00 38.49 38.88 17.60 6.58 3.42 2.50 1.31 0.90 0.81 0.92 2.10 15.50 31.53 26.06 10.77 4.47 2.63 1.71 1.16 0.74 0.68 0.79 1.71 11.95 27.58 21.28 8.10 3.81 2.36 1.44 1.00 0.66 0.59 0.59 1.13 9.19 23.51 15.50 6.04 3.15 1.84 1.21 0.84 0.50 0.46 0.46 0.74 4.86 15.50 9.19 3.94 2.10 1.31 0.91 0.63 0.39 0.35 0.34 0.46 1.84 10.38 5.52 2.63 1.58 0.99 0.71 0.51 0.33 0.31 0.30 0.35 1.21 8.41 4.20 2.23 1.31 0.88 0.64 0.46 0.28 0.26 0.20 0.32 0.91 7.09 3.42 1.97 1.16 0.80 0.58 0.42 0.20 0.22 0.16 0.22 0.64 4.54 2.51 1.58 0.92 0.67 0.45 0.35 Tunnel Gulch Estimated Stream Flow 4 1 3 ~ 2 CJ o JAN Fill MAR APR MAY JLN JUl AUG SEP OCT NOV DEe Month -4-