07/6/A-006 Supplemental Data - Laserfiche WebLink

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S 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 instream flow recommendation for North Fork North Platte River, located in Water Division 6. Location and Land Status. North Fork North Platte is tributary to the North Platte River approximately six miles west of Walden. This recommendation covers the stream reach beginning at the headwaters downstream to the headgate of the Little Nellie Ditch. Approximately 60% of the 7.50 -mile reach is federally owned, while the remaining 40% is privately owned. Biological Summary. North Fork North Platte River transitions from a high gradient to a low gradient stream within the proposed reach. The stream channel is stable and well anchored by a vigorous riparian community. Water quality, food supplies, and substrate are excellent for salmonids. This stream supports one of the best fisheries in North Park. Fisheries surveys indicate self- sustaining populations of brown trout and brook trout, with brown trout specimens of up to 19 inches in length. 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. 7.10 cubic feet per second is recommended for the high temperature period from May 1 to October 31. This recommendation is driven by the average velocity criteria and the average depth criteria. It is important to provide adequate velocity and physical habitat during this time for fish spawning and incubation of eggs. In addition, it is important to provide adequate depth and velocity to maintain low water temperatures, because the lower elevations portions of the reach do not have significant shading and cover. Protecting flows during this time period is also important for recharging the alluvial aquifer, which discharges water to the stream and maintains flow levels during later summer. 5.60 cubic feet per second is recommended from November 1 through April 30. This recommendation is driven by the average depth criteria. This flow rate will allow fish to survive in pools, provide sufficient physical habitat in riffles between pools, and will prevent the riparian environment from being seriously stressed.