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.'4 0 • . DRAFT INSTREAM FLOW RECOMMENDATION 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 recommendation for an enlargement of the existing instream flow water right on Pauline Creek, located in Water Division 4. Location and Land Status. Pauline Creek is tributary to Cochetopa Creek approximately 26 miles south of Gunnison. The stream reach covered by the surveys conducted on BLM lands runs from the confluence with Chavez Creek to the confluence with Cochetopa Creek. Of the _mile reach, approximately % is located on federal lands while the remaining _% is privately owned. Biological Summary. Pauline Creek is a moderate gradient stream with large substrate and good vegetative cover. Fishery surveys indicate that the creek supports a self- sustaining fishery. The stream environment is presently in good condition and provides suitable • substrate, channel stability, water quality, and food supplies for salmonids. However, the stream has a high number of pools and beaver ponds, so spawning locations are limited. Accordingly, it is important to provide stream flows to maintain the limited amount of spawning habitat and to maintain water exchange in pools during low flow periods. R2Cross Analysis. 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. A 2.75 cubic feet per second enlargement is recommended from May 1 to October 31. The existing instream flow water right is 3.5 cubic feet per second year round, so the enlargement would increase the water right to 6.25 cubic feet per second from May 1 to October 31. This recommendation is driven by the average velocity criteria. BLM was concerned that the existing 3.5 cfs instream flow water right did not provide sufficient physical habitat or velocity during the warm weather months, and the R2Cross surveys verified this concern. Water Availability. BLM is not aware of any decreed surface diversions in the proposed reach. Since there are no gages on this stream reach, BLM recommends obtaining data from USGS gage 09118450 ( Cochetopa Creek below Rock Creek) and then using a basin apportionment to obtain an estimate of water availability. When this gage is used, adjustments must be made to account for irrigation diversions located upstream.