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STUDY PLAN The Aspinall Unit and other Bureau of Reclamation projects have reduced the volume of spring runoff in the Gunnison and Colorado rivers. Spring runoff is the most important variable in determining the physical environment of the river during the coming year. This report discusses several ways in which this altered streamflow may have effected the endangered fishes. The purpose of this section is to propose hypotheses and studies to evaluate these possible effects. An important component will be to provide test flows from the Aspinall Unit to facilitate the studies. Because the largest change resulting from the construction and operation of Aspinall (and other Bureau projects) has been to alter the flow regime, the test flows should more closely mimic the natural hydrograph of the Gunnison River (i.e. higher spring flows, and lower fall and winter flows). The unallocated water currently stored in Blue Mesa Reservoir should be used to supply water for the study. The evaluation of the effects of the Aspinall Unit will involve a series of studies, conducted by different organizations, but closely coordinated by the Fish and Wildlife Service and the Bureau of Reclamation. The evaluation will involve five years; however, many of the individual studies can be completed more quickly. The five-year time frame should be sufficient to allow for unforseen problems that could delay completion of individual studies. Also, it is likely that the proposed studies may identify additional questions to be asked. Because of the. large variation in spring flows requested, the ability to release the higher spring flows will be limited in some years because of low snowpack or low storage. Because of this uncertainty, we may not be able to predict more than a few months in advance 31