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technical criteria of 8-foot-wide, 10-foot-long, 3-foot-deep pools; 0.5 • foot of head drop per pool; 1-foot-wide vertical slot; and 1-foot-wide by 1.5-foot-high orifice (slot and orifice inverts placed flush with the ladder floor). With 0.5 foot of head drop per pool and water surf ace difference of 12 feet (at low tailwater), the ladder has 23 vertical s 1 of/orifice weirs and one drop i n water surface elevation at the slide gate fish entrances. For this operational condition, total ladder flow is approximately 18 cfs. b. The reasonable design high flow was chosen as 6,000 cfs passing over the spillway, which is approximately the 80-percentile expected flow for May. At the higher flows, the location of this fish ladder reduces the original design capacity of the spillway. The con- sequence of this reduced capacity is a higher forebay water elevation of approximately 4,516.0 feet. From preliminary computations, tailwater was calculated as elevation 4,567.0 feet. The change in water surface eleva- tion from below to above the dam is then approximately 9.0 feet. With the basic ladder design (23 weirs, 8-foot-wide by 10-foot-long pools) and accounting for the backwater effect into the ladder, the head drop will gradually vary from 0.2 foot at the downstream end of the ladder to 0.5 foot at the upstream end of the ladder. For this operational condition, the total ladder flow is approximately 22 cfs. c. For flows above 6,000 cfs and below 8,000 cfs, the ladder should be closed at the forebay entrance. The upstream barrier wall elevation is 4,578.0 feet and will protect the ladder from high riverflows. If the ladder was open at the upstream end, the ladder structure would be overtopped by water and not functional for fish passage. d. For flows above 8,000 cfs to 24,500 cfs, the spillway will carry the majority of the riverflow with approximately 1 foot of freeboard allowed at the maximum flow. The ladder itself will be over- topped, also passing a portion of the floodflow. e. For the standard operational conditions, auxiliary water must be added at the entrance diffuser to provide better fish attraction conditions. The total quantity of auxiliary water is three times the ladder flow quantity. Each entrance slide gate opening and amount of auxiliary flow can be adjusted to attain the desired head drop at that entrance. • 18