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~ IN REPLY REFER TO United States Department of the Interior BUREAU OF LAND MANAGEMENT Colorado State Office 2850 Youngfield Street Lakewood, Colorado 80215-7093 CO-932 7250 www,co.blm,gov '1Ee 1 5 2004 Mr. Dan Merriman Colorado Water Conservation Board 1313 Sherman Street, Room 721 Denver, Colorado 80203 Dear Mr. Merriman: The Bureau of Land Management (BLM) is writing this letter to formally communicate its instream flow recommendation for Horsefly Creek, located in Water Division 4. Location and Land Status - Horesefly Creek \s tributary to the San Miguel River approximately 13 miles east ofNaturita. The stream reach covered by the surveys conducted on BLM lands runs from the confluence with Sheep Creek to the confluence with the San Miguel River. The entire 5.21 mile reach is located on federal lands. Biological Summary - Fishery surveys indicate that the stream environment supports a self-sustaining population of speckled dace. This stream segment also provides important habitat for migratory brown trout from the San Miguel River and spawning habitat for rainbow trout from the San Miguel River. Low flows are common in the late summer and fall, but the stream channel provides plentiful pools to insure fish survival during low flow periods, The stream environment occasionally experiences flash flooding, but the steam channel is stable, with a well-established riparian community and well-anchored substrate. RlCross Aualysis - BLM's data analysis, coordinated with the Division of Wildlife, indicates that the following flows are needed to protect the fishery and natural environment to a reasonable degree. 13,00 cubic feet per second is recommended for the snowmelt runoff period from April I to June 15. This recommendation is driven by the average depth criteria. Maintaining the average depth criteria is important for speckled dace spawning and for providing additional physical habitat for trout that move up into the creek from the San Miguel River during snowmelt runoff. Protecting snowmelt runoff flows is also important for recharging the alluvial aquifer, which discharges water to the stream and maintains flow levels during later summer. BLM is not making an instream flow recommendation for the remainder of the year. Naturally low flows, combined with upstream irrigation diversion, results in extremely low flows during the remainder ofthe year. Speckled dace are able to survive in pools with this very low flow, but the available flows do not meet any ofthe instream flow criteria for riffle habitats. Accordingly, BLM recommends that CWCB make an appropriation only for the snowmelt runoff season, and that CWCB appropriate additional water at other times of the year only if additional flows become available.