Gunnison - Paonia Reservoir Sedimentation Study Application

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. . . 5. Environmental enhancements will result from this project in relation to the potential destructive consequences that will otherwise occur as a result of continued, unrestrained sedimentation. As mentioned above, continued sedimentation will result in a completely sediment filled reservoir basin and may necessitate replacement of the storage capacity at one or more other sites with the attendant environmental repercussions. Additionally, ifno action is taken, the sedimentation delta will eventually surround the intake structure, and the ability to control the rate for release of sediment from the reservoir will be decreased. Sediment releases may occur episodically, in slugs and with unavoidable negative environmental impacts. 6. The most easily developed and productive reservoir sites are always used first. One rule of thumb is that the difficulty of developing the second generation of storage facilities to provide similar function increases by a factor of2 or 3. Therefore, instituting a sustainability plan for Paonia Reservoir will avoid the costs, disruption and environmental impacts of developing one or more alternative storage sites. In fact, due to geographical, geologic, environmental or other constraints it may not even be possible to locate and develop alternate storage sites that will produce the same benefits, storage volume, etc. Also, sediment loads against the dam reduce its stability and increase safety risks. Reduction of these loads will avoid costly dam modifications which may be otherwise necessary to buttress the embankment against potential failure 7. If the sedimentation continues at current rates, the impact on the dam's outlet works may start to restrict the range of allowable operational flexibility due to downstream environmental and other considerations. Therefore, one of the benefits of developing a plan to control sedimentation impacts will be to maintain current operational versatility. 8. The project will comply with all applicable laws, regulations and will protect all existing water rights. k. Water Conservation and Efficiency - Enhancement of water conservation and use efficiency is not a direct goal of this project. However, increasing the security of existing water storage capacity is a means to conserve existing water supplies and protect existing water rights. Improving long term viability of the storage capacity can be considered a step to improve the efficient use of existing facilities. I. Water Conservation Plan - The Delta Soil Conservation District prepared a water management plan for the NFWCD. This plan is entitled "North Fork Water Management Plan" and is dated July, 2001. The plan was prepared in coordination with and was funded by the U.S. Bureau of Reclamation and included Paonia Reservoir. This plan includes water conservation aspects. 111. Development of New Water - No new water supplies will be made available as a direct result of this project. However, relative to the unavoidable loss of storage that will occur without mitigation efforts, there is an aspect of new storage development. For example, dredging sediments from the basin is similar in effect to enlarging the reservoir capacity.