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Enclosure 4- San Miguel River Instream Flow Recommendation <br />Water Availability <br />The Bureau of Land management (BLM) and Colorado Division of Wildlife (CDOW) staff <br />conducted an evaluation of the stream hydrology to determine if water was physically available <br />for the instream flow recommendation. The hydrograph below was derived from data collected <br />by the United States Geological Survey (USGS) stream gage for the San Miguel River at Uravan, <br />CO ( #09177000), which has a drainage area of 1500 square miles (See Gage Summary in <br />Appendix C). The total drainage area of this segment of the San Miguel River is approximately <br />1500 square miles. The period of record for this gage was 1954 to 2004, the period of record <br />used by staff in their analysis was 1954 - 2004, or 50 years of record. Table 2 below displays the <br />estimated flow of the San Miguel River at the gage, in terms of a percentage of exceedence. <br />Exceedences <br />January <br />February <br />March <br />Aril <br />May <br />June <br />July <br />August <br />September <br />October <br />November <br />December <br />1% <br />162.9 <br />351 <br />1044 <br />3750 <br />4123 <br />2808 <br />1770 <br />958.5 <br />612 <br />432 <br />370.6 <br />217.8 <br />5% <br />140 <br />186.1 <br />578.2 <br />2610 <br />2700 <br />2240 <br />1102 <br />5971 <br />371 <br />292.1 <br />212 <br />160 <br />10% <br />130 <br />155.7 <br />383.2 <br />1900 <br />2220 <br />1770 <br />868 <br />424,1 <br />301 <br />252 <br />182 <br />148 <br />20% <br />120 <br />130 <br />252 <br />1260 <br />1724 <br />1380 <br />633.4 <br />265.6 <br />201 <br />199 <br />152 <br />121 <br />50%: ' <br />" 80 <br />97 <br />128 <br />550 <br />943 <br />820 <br />301 <br />125.5 <br />88 <br />116 <br />100 <br />85 <br />8no <br />62 <br />70 <br />83 <br />233 <br />484 <br />437 <br />112 <br />51.2 <br />42 <br />76.6 <br />73 <br />65 <br />90% <br />55 <br />61 <br />70.8 <br />130 <br />271 <br />298 <br />61 <br />27 <br />29 <br />53.8 <br />fit <br />57 <br />95% <br />48 <br />55 <br />62 <br />96 <br />140.9 <br />215 <br />34 <br />20.55 <br />23 <br />33 <br />52 <br />50 <br />99% <br />40 <br />40.73 <br />47 <br />55 <br />61.9 <br />38 <br />6.63 <br />5.91 <br />14 <br />20 <br />32 <br />36 <br />Table 2: Estimated Stream Flow for SAN MIGUEL RIVER <br />Table 2 shows that the spring flow recommendation of 325 cfs, is available at least 50% of the <br />time, April 15 through ,tune 30. The high flow summer recommendation of 170 cfs, is available <br />at least 50% of the time, July 1 through July 31. The low flow summer recommendation of 115 <br />cfs, is available at least 50% of the time, August 1 though August 31 and March 1 through April <br />14. The winter recommendation of 80 cfs, based on water availability concerns, is available at <br />least 50% of the time, September 1 through February 29. However, if additional water is <br />determined to be available in further investigations, the CDOW and the BLM would recommend <br />enlarging the wintertime recommendation up to 115 cfs, to preserve the natural environment to a <br />reasonable degree. <br />