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1 1 1 Evaluation of Diversion Structures Structures Within Designated Critical Habitat Pump Diversions Between Juniper and Cross Mountain Canyons 1 1 While these diversion structures were only viewed from the air, many of them displayed a common characteristic--namely, an extensive shallow braided channel downstream of the structure caused by instream construction activities at the structure itself. In many cases these alluvial berms extend only part way into the river, but in some cases they extend most of the way across the river. This feature, in conjunction with the poor approach channel characteristics, probably make some of these pump diversions difficult for fish to navigate during low flow conditions. Accordingly, we believe they merit further, more detailed evaluation. Maybell Canal The Maybell Canal is the largest and most permanent diversion structure on the Yampa River mainstem. It also lies well within designated critical habitat. Although there is evidence that fish can pass the Maybell Canal diversion, no detailed studies have been conducted at the ' structure. During the latter part of most irrigation seasons, and throughout the fall and winter in low flow years, it is reasonable to consider the Maybell Canal a major obstacle to fish passage. We recommend it be given further attention. Patrick Sweeney-K. Diamond Ditch 1 7- L 1 The Patrick Sweeney/K. Diamond diversion a few miles upstream of the Maybell Canal should also be considered a significant obstacle to fish passage. Under lower flow conditions the configuration of the structure will draw upstream migrating fish away from the true passage channel near the pump intakes. Accordingly, we recommend it be given further attention. Structures Upstream of Designated Critical Habitat Deep Cut Ditch 1 ri This temporary gravel structure is, in some ways, typical of many other diversions along the mainstem. However, its proximity to designated critical habitat and the extent of river blockage suggest it be examined more closely. While it was the conclusion of the site visit team that the structure was passable to fish via the constructed lowflow notch in the main berm, a more comprehensive monitoring effort over an entire migration cycle would answer the question more definitively and might shed light on how other similar structures might be better constructed, still using conventional methods, to allow fish passage. Cary Ditch Although it is outside designated critical habitat, this structure deserves further study by virtue of its extent; it is probably difficult for fish to pass since the are multiple structures to 3-9