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<br />001587 <br /> <br />profile and geometry. The R2CROSS technique is highly dependent on stream channel <br />geometry. Additional stream cross section information might need to be collected in <br />areas where the stream channel dimensions approximate those being contemplated in the <br />mitigation proposal. <br /> <br />III. Mitigation concerns/recommendations/opportunities. <br /> <br />The BA does not provide a reservoir operation plan that describes the proposed storage or flow <br />release schedule and how this could affect native fishes in the La Plata River. Native fishes in the <br />La Plata River between Long Hollow and Cherry Creek are largely dependent on irrigation <br />return flows. Ifthe construction and operation ofthe reservoir makes additional irrigation <br />depletions in the Cherry Creek basin possible, then the Long Hollow Reservoir project could <br />adversely affect the fishery in the La Plata River from Long Hollow to Cherry Creek. This <br />aspect of the project needs to be adequately evaluated, described, and analyzed for <br />environmental impacts. If flows in this reach are depleted as a result ofthis project, then <br />additional mitigation will need to be addressed. <br /> <br />With Long Hollow Reservoir, there may be opportunities to fine-tune the administration of water <br />rights on the La Plata River to accommodate new irrigation, protect native fishes, and rneet La <br />Plata River Compact requirements. A comprehensive water management agreement could be <br />developed that describes how water rights would be administered in the future to meet La Plata <br />Compact requirements, irrigation needs, and native fish needs. Minor changes to water rights <br />administration on the La Plata River could provide mutual benefits to irrigators and native fishes. <br />For example, fall stock water delivery could be rnodified to provide additional water for native <br />fishes. Diversions during the non-irrigation season below Long Hollow could be curtailed to <br />provide additional water for native fishes and reduce the need for bypass flows from Long <br />Hollow Reservoir. Any changes made in water management that improve stream flows for <br />native fishes must be permanently protected in some manner. <br /> <br />Increased selenium concentrations in irrigation return flows are a concern for the reproductive <br />health of native fishes, especially since releases from Long Hollow Reservoir would occur <br />during the spring and summer spawning period. The temperature of water released from Long <br />Hollow Reservoir is another concern for native fishes, which generally prefer warm water (65-75 <br />degrees F) during the summer months. The BA should address water quality parameters, <br />including temperature and selenium, as they may affect native fish and wildlife populations in <br />the area. <br /> <br />Measures should be taken to prevent establishment of non-native fishes in the La Plata River 1 <br />from Long Hollow Reservoir. Native fishes are not able to compete successfully with introduced \ <br />non-native fishes. Roundtail chubs are particularly vulnerable to predation by non-native fishes <br />like bass, catfish, and sunfish. Native flannelmouth and bluehead suckers will readily hybridize <br />with introduced white suckers. Non-native fishes eventually become established in most <br />reservoirs, generally through stocking or illicit introductions. The following measures are <br />recommended to prevent establishment of non-native fishes in Long Hollow Reservoir: <br />1. Install fish screens on all reservoir outlets. Fish screens should have a 14 inch rnesh size. <br /> <br />4 <br />