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water depth of 12 feet (measured from the upstream concrete apron} is • required to maintain this required flow for power generation. 2. During periods of high flow (spring runoff), the upstream water level may exceed 12 feet. RWPC then regulates the headgates (reduces the size of the open area) to maintain the desired flow, The diversion dam was originally designed to pass 30,000-cfs flaodflow5 with approximately 1 foot of freeboard allowed. Since construction of the existing dam, several upstream regulating dams have been- built vn the Gunnison River. Hydrologic information in Appendix B shows simulated riverflows with the present upstream regulation. 3. During periods of law flow, the upstream water level will fall below 12 feet. RWPC then periodically places a number of flashboards on the crest of the spillway which essentially reduces the crest length. The upstream water level then raises up to the 12-foot depth to pass the riverflow over the shortened spillway crest. During the lowest flow periods, the flashboards are placed across the entire crest tv maintain the desired upstream water level. Between the times when flashboards are placed on the crest, flow depth at the headgates is also regulated by opening and closing the sluice gates. 4. The flashboards are normally placed on the crest beginning at the left abutment and proceeding- toward: the right abutment. This sequence of placement is used because of the method of installing the flashboards.. Cables suspended above the crest of the dam guide a cart carrying dam personnel who manually place the flashboards. The first flashboard is placed near the sluice gate structure (on the left abut- ment) because of ease of access to the spillway crest in the suspended cart. 5. The power canal is dewatered for 1 week in the fall (after the irrigation season) and 1 week in the spring (before the irrigation season) for inspection and maintenance. Maintenance usually consists of sediment and- debris removal from the upstream portion of the power canal. C. Endangered Species Background. 1. The Colorado squawfish and razorback sucker, two na ive fishes once abundant in the Colorado River system, are threatened with extinction. The steady decline in their range and abundance has coin- cided with the activities of technologic man in the Colorado River basin. However, the exact factors that have caused decline of these fishes are not well understood. It has been speculated that the decline of these fishes has occurred since the early 1900's, and that much of the decline is the result of changes to their native habi-tats brought about by stream • alteration. Colorado squawfish exists in about 25 percent of its original 2