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Evaluation of Diversion Structures island, contains a constructed arch-shaped lowflow notch. The ditch headgate exists on the left , river bank at the downstream end of the island. The side channel is blocked with a smaller secondary gravel dam below the headgate. The main gravel berm causes about a one foot drop , in water surface. Annual re-construction of the diversion berm has created a large disturbed area downstream, but the lowflow notch probably allows passage of fish. The local habitat disturbance occurs annually and may have moderate impact to benthic fauna and resident fish species. ' City of Craig Diversion The City of Craig diversion consists of a permanent concrete and rip-rap cut-off wall , designed to maintain water levels at the pump intake a short distance upstream. The structure was designed to allow upstream and downstream passage of fish, as well as downstream boat passage. Photographs and design drawings of the structure are found in Appendix B. BIO/WEST (1992) conducted field studies on radio-tagged native fish to assess passage and ' migration. No Colorado squawfish were collected near the structure and none were observed in the vicinity, however, the native fish species used as surrogates were able to move past the structure. Physical habitat measurements taken at the structure showed that velocities in the fish passage notch ranged from 3.3 feet per second (fps) up to 7.4 fps (Masslich, 1993). Depths at a flow of 170 cfs ranged from 0.7 ft to 1.4 ft. The average velocity of 4.5 fps and the range of depths are within the range of those utilized by Colorado squawfish in other areas of the upper Colorado River basin. MassIich (1993) concluded that at extreme low flows other natural features in the river would inhibit passage before the City of Craig structure became impassable. This type of structure may be a suitable prototype for other diversion structures that are now reconstructed annually. Mack Ditch , The Mack Ditch diverts from the right bank of the Yampa River a short distance downstream of the State Highway 13 bridge below the City of Craig. It lies within designated ' critical habitat for the endangered fish. The diversion consists of a pump which draws water from a small side channel and raises it into a ditch on the bluff. There is no evidence of any recent instream activity or construction related to this diversion and it is believed to have little potential to adversely affect fish migration. Lowry Seely Pump This diversion is located on the right bank of the river roughly four miles upstream of , Government Bridge. It consists of a pump which raises water into a ditch on the right bank river terrace. While the diversion was not viewed close-up, it did not appear that there were any instream structures of any consequence associated with it. Accordingly, it is believed to have little potential adverse effect on local habitat or on fish passage. I 3-4 1