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. . . 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 in stream flow enlargement on lower Corral Creek, located in Water Division 5. The existing instream flow water right on this creek is 1.5 cubic feet per second, year round, from the headwaters to the confluence with the Colorado River, a distance of 12 miles. The existing instream flow water right was established in 1986. Location and Land Status. Corral Creek is tributary to the Colorado River approximately five miles west of Hot Sulphur Springs, Colorado. The creek is located within the upper Colorado River watershed in Grand County. This recommendation covers the stream reach beginning at the confluence with Smith Creek and extending downstream to the confluence with the Colorado River. All of the land along 2.75 mile reach is owned and managed by the BLM, with the exception of '/4 mile of private land. Biological Summary. Corral Creek is a high gradient stream with variable substrate size, ranging from reaches dominated by gravels to reaches dominated by cobbles and boulders. Much of the reach covered by this recommendation is confined by narrow canyons. In the upper part of the reach, beaver activity is widespread, with short rimes between beaver dams. The lower part of the reach is characterized by plunge pools separated by short rimes. The riparian community provides substantial shading and nutrient supply for the creek, and it provides numerous pools and overhanging banks for the fish population. Fishery surveys indicate that the creek supports a self-sustaining population of brook trout with a variety of age classes. 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 during the high temperature period from April I through October 31, bringing the total instream flow right up to 4.25 cubic feet per second. This recommendation is driven by the average velocity criteria and average depth criteria. Because the creek is characterized by short rimes between numerous beaver ponds and plunge pools, it is very important to maintain adequate velocity and depth in the limited rime habitat. A 0.9 cubic feet per second enlargement is recommended for the cold temperature period from November 1 through March 31, bringing the total instream flow water right up to 2.40 cubic feet per second. This flow rate should allow passage