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<br />_'7 <br /> <br />~ <br />--. <br /> <br />IK REPLY REFER TO: <br /> <br />United States Department of the Interior <br /> <br />BUREAU OF LAND MANAGEMENT <br />Colorado State Office <br />2850 Youngtield Street <br />Lakewood, Colorado 80215-7093 <br /> <br /> <br /> <br />www.co.blm,gov <br /> <br />CO-932 <br />7250 <br /> <br />DEe 1 9 {c102 <br /> <br />Mr. Dan Merriman <br />Colorado Water Conservation Board <br />1313 Sherman Street, Room 721 <br />~enver, Colorado 80203 <br /> <br />Dear Mr. Merriman: <br /> <br />The Bureau of Land Management (BLM) is writing this letter to formally communicate its <br />instream flow recommendation for Dorsey Creek, located in Water Division 3. <br /> <br />. <br /> <br />Location and Land Status: Dorsey Creek is tributary to San Luis Creek approximately 12 miles <br />northwest of the town Villa Grove. The stream reach that was surveyed begins at the BLM <br />Forest Service boundary and runs approximately 2.5 miles to the confluence with San Luis Creek. <br />One mile of the reach flows through private land, while the other 1. 5 miles of the reach flows <br />through BLM lands. <br /> <br />Biological Summary: Fishery surveys indicate that the stream environment is in stable condition, <br />and supports a self-sustaining brook trout fishery. Channel stability, bank stability, and substrate <br />are good for salmonids. This type of stream environment has steep gradients that typically limit <br />the available pool habitat and food supply. If the continued existence of the fishery is to be <br />assured, it is important to provide stream flows that protect the limited amount of available <br />habitat. <br /> <br />R2Cross Analysis: BLM collected two data sets on Dorsey Creek To develop this <br />recommendation, BLM identified the flows needed to meet instream flow criteria in each data set, <br />and then averaged these flows to develop a recommendation for the entire stream reach. BLM <br />recommends the following flows to protect the natural environment to a reasonable degree: <br /> <br />. <br /> <br />0.8 cubic feet per second is recommended for the May 1 to October 31 <br />high temperature period. In both cross sections surveyed, this flow meets <br />both the wetted perimeter and average depth criteria. This flow also meets <br />the average velocity criteria in one cross section and provides 0.9 feet per <br />second average velocity in the other cross section. <br />