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Evaluation of Diversion Structures ' b erm has a constructed rock-lined low-flow notch at its far right end. The diversion causes about a one-foot drop in water surface and appears to be partly reconstructed every year using alluvium from the downstream area. This has caused a braided channel to form downstream of the diversion. ' The low-flow notch in this structure is constructed of large rip-rap. The space between the rip-rap is probably large enough for fish to pass but the lack of a well-defined downstream approach may delay fish passage through the structure. This type of structure could be a ' moderate obstacle to upstream passage if the rock rip-rap is placed too close together. The disturbance associated with annual reconstruction poses a moderate impact to riverine and riparian habitat. Cary Ditch The Cary Ditch is located downstream of Hayden, above designated critical habitat but possibly within occupied habitat. The structure consists of a semi-permanent berm, constructed of gravel alluvium, fully blocking the main (right) channel of the river at the downstream end of a large island. This berm directs flow to a headgate on the right river bank adjacent to Highway 40. Construction of this main berm is facilitated by the construction of a second gravel berm at the head end of the island. This second berm serves as a "cofferdam" ' to divert flow around the left side of the large island while the main berm is re-built; the second berm is then partly breached once the main diversion is constructed. A third smaller gravel berm blocks the left river channel apparently to create a pool for an unrelated pump diversion on the left bank. The main gravel berm near the Cary Ditch headgate causes about a 1.5-foot drop in water surface. The diversion requires partial reconstruction every year. ' Local habitat disturbance at the Cary Ditch diversion is higher than any other structure visited. Periodic construction of the diversion dam has caused a large braided area to develop downstream. Similar habitat disturbance exist at the two other gravel berm sites. The rock base of the main diversion dam may allow fish passage, but is believed to represent a moderate obstacle to such movement. ' Brock Ditch The Brock Ditch diversion is located roughly seven miles upstream of the confluence of Elkhead Creek, above designated critical habitat but possibly within occupied habitat. The diversion consists of an inlet channel on the right bank of the river leading to a headgate set in a concrete wall. There is evidence of some instream construction of a gravel berm, but this appears to be several years old. There is currently no structure within the river channel. Accordingly, the Brock Ditch diversion is believed to have little potential effect on migrating fish species. ' Deep Cut Ditch The Deep Cut Ditch is located about four miles east of the City of Craig and below the Elkhead Creek confluence. It is above designated critical habitat but possibly within occupied habitat. The diversion consists of a temporary gravel berm blocking about 75 percent of the river and extending from the upper end of an island near the left bank upstream to the right ' bank. The berm, which directs river flow into the side channel between the left bank and the 1 3-3