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Gunnison River /Aspinall Unit Temperature Analysis -Phase I .Page 5 3. ANALYSIS OVERVIEW As stated previously, this project was split into two phases because the Recovery Program felt it would be wise to conduct a feasibility and scoping study of Gunnison river temperatures before investing the time and money in developing comprehensive models of the system. The results and recommendations from this first phase would then form the basis for deciding whether or not to pursue a more rigorous modeling exercise. Given this objective, we conducted a limited analysis of the data to determine what, if any, conclusions could be drawn with respect to the prospects for increasing stream temperatures near Delta.. There is considerable evidence that the Aspinall Unit reservoirs have impacted temperatures near Delta (e.g. Stanford, 1994, Osmundson 1999). What we want to evaluate here is the degree to which the reservoirs impact stream temperature, and whether or not structural or operational modifications to the reservoirs could be used to warm the river near Delta. Accompanying this central question are a host of other physical and institutional questions that need to be addressed. Some of these basic questions and analyses that we have attempted to address include: • What general trends in water temperatures can be discerned from the data? • What are the impacts of season, release temperature, meteorological conditions, and flow on these trends? • Are there significant tributary impacts? • What does the thermal regime of the Aspinall Unit reservoirs look like? • What immediate conclusions can we draw from the reservoir data? Clearly some of these questions will require a more in-depth modeling exercise to address fully. However, some preliminary analysis of the data indicates that prospects are good for using the Aspinall reservoirs to obtain warmer stream temperatures near Delta. Again, we remind the reader that we are simply addressing whether or not temperature control is possible; there are a host of other factors both physical and institutional that may further constrain any temperature control options. The following data analysis is split into two sections, one focusing on reservoir temperatures, the other on river temperatures between Crystal Dam and the town of Delta. Hydrosphere Resource Consultants