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Evaluation of Diversion Structures Henry Sweeney Ditch The Henry Sweeney Ditch is located on the left bank of the river roughly three miles upstream of Government Bridge. It consists of a small gravel berm extending a short distance into the river channel. The berm serves to direct a portion of river flow toward a pump which 1 serves a ditch along the left river terrace. Construction of the small berm is not believed to represent a significant habitat disturbance and it does not present any obstacle to fish migration. ' K. Diamond/Patrick Sweeney Ditch The K. Diamond/Patrick Sweeney Ditch diversion is located about a mile downstream of Government Bridge. It consists of a relatively permanent rock-fill structure blocking roughly 75 percent of the river. The rock size used is approximately 2-foot diameter. The structure is perpendicular to river flow and directs flow toward the right bank into a small channel where two pumps and a gravity headgate exist. The current structure is two years old and overtopping flows during peak runoff months have caused the rock to collapse downstream and sink into the bed leaving two small breaches in the berm. The structure causes approximately a one-foot water surface drop. . Because of its relative permanence, there is not a lot of habitat disturbance associated with this diversion. However, the structure may block upstream fish passage at extreme low flows. Although fish may move upstream through the side channel, they must back-track from the rock dam to find and navigate through the side channel. Old Sweeney Ditch ' This diversion is located on the left river bank not quite two miles downstream of Government Bridge. It consists of several small berms extending part way into the river; a pump is located just below one of these berms. The configuration of the berms suggests that they serve ' as erosion-control groins as well as creating a pool at the pump intake. None of the berms extends more than 20 feet into the river and none would represent an obstacle to fish movement. Maybell Canal The Maybell Canal is located in Juniper Canyon about four and one-half miles upstream ' of the Highway 40 bridge. It is the largest and most permanent of the diversion structures examined. The diversion consists of a rock dam fully blocking the river with large boulders apparently taken from the adjacent canyon sides. The dam diverts river flow towards the right ' bank into a perched canal; excess diversions are passed back to the main channel in a side- channel spillway fashion. The rock dam creates a water level difference of over five feet. Annual habitat disturbance seems to be minimal based on observations during the summer ' of 1994. The large rock at this structure and in the downstream channel probably make fish passage difficult; however, Colorado squawfish have migrated past this structure in past years. The potential impact to migration and local passage is the greatest at this structure due to its size and ability to withdraw the majority of river flow. Passage was not possible at low flow conditions observed in August of 1994. 1 3-5