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<br />Table I: Data
<br />
<br />Party Date Q 250% -40% Summer (3/3) Winter (2/3)
<br />BLM 07/29/2004 3.32 1.3 - 8.3 2.64 0.52(1)
<br />BLM 10/16/2003 1.36 0.5 - 3.4 1.19 1.14
<br />
<br />BLM = Bureau of Land Management DOW = Division of Wildlife
<br />(1) Predicted flow outside of the accuracy range of Malll1ing's Equation. ? = Criteria never met in R2CROSS Staging Table.
<br />
<br />Biologic Flow Recommendation
<br />
<br />The summer flow recommendation, which meets 3 of 3 criteria and is within the accuracy range
<br />of the R2CROSS model is 2.0 cfs (See Table I). This recommendation was derived by
<br />averaging the results of two cross sections. The winter flow recommendation, which meets 2 of
<br />3 criteria and is within the accuracy range of the R2CROSS model is 1.0 cfs (See Table I). It is
<br />our belief that recommendations that fall outside of the accuracy range of the model, over 250%
<br />of the measured discharge or under 40% of the measured discharge, may not give an accurate
<br />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 Animas River at Howardsville, Colorado (ID #09357500), which has a
<br />drainage area of 55.90 square miles (See Gage Summary in Appendix C). The total drainage
<br />area of Deer Park Gulch is approximately 3.7 square miles. The period of record for this gage
<br />was 1935 to 1982, the period of record used by staff in their analysis was 1935 - 1982, or 47
<br />years of record. Table 2 below displays the estimated flow of Deer Park Creek at the gage, in
<br />terms of a percentage of exceedence.
<br />
<br />Table 2: Estimated Stream Flow in Deer Park Creek
<br />Exeeedenees Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nav Dee
<br />10/0 1,7 1,5 2,1 14,6 46,6 69.2 49,5 17,9 14,3 10,0 4,2 2,1
<br />50/0 1,5 1,3 1,5 9,5 36,8 53,5 37,2 10.4 8,7 5,5 2,8 1,8
<br />10% 1,3 1,3 1,3 6,7 32.4 48,6 30,0 8,7 6,5 4.4 2,6 1,6
<br />20% 1,3 1,2 1,2 4,8 25,8 41.4 21,5 7,1 4,3 3,2 2,2 1,5
<br />80% 0,9 0,9 0,9 1,2 6,8 17,0 5,7 2,7 1,9 1,5 1,1 1,0
<br />90% 0,9 0,8 0,7 1,0 4,8 13,7 4,1 2.2 1,7 1,3 1,1 0,9
<br />95% 0,8 0,7 0,7 0,9 3,5 12,0 3,2 2,0 1,5 1,2 1,0 0,9
<br />99% 0,7 0,7 0,7 0,7 1,6 7,5 2,5 1,7 1,3 1,0 0,8 0,8
<br /> 1,0 1,0 1,0 1,0 1,0 1,0 1,0
<br />For this reach, the hydrograph shows that the summer flow recommendation of 2.0 cfs is
<br />available only from May I to October 31. The hydrograph also shows that the winter flow
<br />recommendation of 1.0 cfs is available from November I through April 30.
<br />
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