STATE OF IDAHO FISH AND GAME DEPARTMENT John R. Woodworth, Director EVALUATION OF FISH FACILITIES BROWNLEE AND OXBOW DAMS By James R. Graban Fishery Biologist May, 1964 EVALUATION OF FISH FACILITIES AT BROWNLEE AND OXBOW DAMS INTRODUCTION On August 4, 1955, the Idaho Power Company was licensed, through Federal Power Commission Project 1971, to construct a three-dam complex, consisting of Brownlee, Oxbow, and Hells Canyon hydroelectric dams on the middle Snake River. On November 17, 1960, the F.P.C. issued an order to Idaho Power Company to consult and cooperate with the Department of Interior and the fisheries agencies of the States of Idaho, Oregon, and Washington, to determine a mutually-satisfactory program for the purpose of testing and evaluating the fish facilities at the Brownlee and Oxbow projects. The costs of which program shall be born by the licensee. In February, 1961, the Idaho Fish and Game Department signed an agreement with Idaho Power Company to begin the fish facility evaluation study at Brownlee and Oxbow Dams on the Middle Snake River. The evaluation study was conducted under the general supervision of a steering committee, consisting of representatives of the fish and game agencies of the States of Idaho, Oregon, and Washington, the Idaho Power Company, and the Department of Interior. Field supervision was provided by the Idaho Fish and Game Department. The study spanned a period of three years and is concerned with evaluating the upstream and downstream facilities for passing migratory game fish past the two dams, to determine if the fish-passage facilities function at designed, and to recommend changes in fish passage conditions or request other passage facilities. Figure 1 shows the relative locations of Brownlee and Oxbow Dams. Brownlee Dam, the larger of the two completed hydroelectric projects, was completed in 1958 (Figure 2). Oxbow Dam, located about 12 miles downstream from Brownlee Dam, was completed in 1961 (Figure 3). DESCRIPTION OF PROJECTS AND PERMANENT FISH Brownlee Dam Brownlee Dam is a rock-fill, clay-core structure which creates a gross head of 277 feet and has a crest width of 1,320 feet. Brownlee is a high head dam with a storage reservoir approximately 58 miles long, which undergoes a maximum fluctuation of 101 feet in surface levels. Usable storage capacity is 1,000,000 acre feet, The primary function of the project is power generation at a powerhouse on the Idaho shore. A single spillway is located on the Oregon shore. Additional regulation of the forebay is provided by flood ports; otherwise, all discharge from the project is through the turbines draft tubes. Power is produced with Francis-type turbines. The U. S. Army Corps of Engineers requires Brownlee Reservoir to be drawn down at least 43 feet by March 1 of each year for flood control. A barrier net facility for collecting downstream migrant fish is located in the impoundment approximately one mile upstream from the dam(Figure 4). There is no upstream fish passage facility at Brownlee Dam because adults collected at Oxbow Dam are truck-transported past both structures. -1- Oxbow Dam Oxbow Dam consists of a rock-fill, clay core-dike, having a gross head of 117 feet and a crest width of 945 feet. Oxbow Dam, completed in 1961, is a river-run type project with a relatively low head and small impoundment, The reservoir has a usable storage capacity of 5,500 acre feet and extends 12 miles upstream to the base of Brownlee Dam. The dam has two spillways, a fuse plug structure for emergency use on the Idaho shore and conventional concrete structure on the Oregon shore. With the exception of flows released to maintain fish attraction to the upstream fish facility at the base of the dam or spillway releases, all discharge from the reservoir is through Francis-type turbines. Oxbow Dam is located at the upstream end of a large "oxbow" with a power plant positioned at the lower end, a distance of 2.5 miles (Figure 3). Two conduits, which penetrate a rock promontory forming the inside shore of the "oxbow", carry water to the power plant. It is thus necessary for upstream migrating salmon and steelhead to pass through the influence of the powerhouse tailrace and adjust to the much smaller volume of flaw around the "oxbow" provided to attract fish to the upstream migrant fish facility at the base of Oxbow Dam on the Oregon shore spillway. EVALUATION OF UPSTREAM MIGRANT FISH FACILITIES Description of Upstream Facilities The upstream fish facilities at Oxbow consist of a short fishway section to attract and collect upstream migrants and a trap to hold and transfer fish to transport trucks for hauling around the dams. The facility is similar to a prototype on the White River near Buckley, Washington. A similar facility is also used on a part-time basis for passing upstream migrants at Pelton Dam on the Deschutes River, Oregon, and North Fork Dam on the Clackamas River. Fish enter the short fishway section (Figure 5), swim over a finger-weir into a holding pool, and continue through a louvred V-entrance into a brail compartment with a sloping floor which, when raised, forces them over a white counting board into a hopper. The water-filled hopper is moved mechanically inside a superstructure to a position over a water-filled fish transport truck. The hopper is lowered until the hopper probe is inserted and sealed into a hatch atop the fish truck. Fish are gradually transferred within a water column from hopper to fish truck by a control valve at the hopper base while water is simultaneously discharged from the truck tank. Evaluation of Upstream Migrant Collection at the Oxbow Dam Trap Experiments were conducted to determine the effects on upstream migrant collection at the Oxbow Dam spillway fish trap of (1) water flows from the Oxbow powerhouse and (2) the volume of water flow around the "oxbow." The Oxbow spillway fish trap is located on the upstream side of the "oxbow" while the outlet of the Oxbow Dam powerhouse is located on the downstream side (Figure 3). In the spring of 1961, the Oxbow pool was being filled and no water was released through the Oxbow powerhouse until late May. The only water discharged from Oxbow Dam was bypassed around the "oxbow," Thus, in May, 1961, fish migrating upstream were not subjected to the influence of the Oxbow tailrace discharge as were those in May of 1962 when the powerhouse was in operation. On May 11 and 12, 1961, 17 chinook salmon and four steelhead trout were taken from the Oxbow spillway trap, tagged, transferred to tank truck, and released downstream in the Snake River near Homestead, Oregon, a distance of five miles. On May 3 and 10, 1962, 15 chinook salmon and 14 steelhead were taken from the trap, tagged, and released downstream in the same area as the 1961 release. The number and rate at which these fish returned to the Oxbow spillway trap is shown in Table 1. A second experiment was conducted to determine if a flow of 1,000 c.f.s. was necessary to attract fish round the "oxbow" to the spillway trap. At the beginning project operations, Idaho Power Company was required under Federal Power Commission order to maintain a continuous flow of 1,000 c.f.s. around the "oxbow" to attract upstream migrating fish to the spillway fish trap. An experiment was conducted to determine if such a flow was necessary to attract fish around the "oxbow" to the spillway trap. This study was a cooperative effort by the Idaho Power Company, the Federal government, and interested states under the approval of the Federal Power Commission, The relationship of water flows around the bow to fish counts for 1962 is shown in Figure 6. There appears to be no consistent relationship between changes in flow and fish movement, On October 1, 1962, the salmon and steelhead count was 120 fish and on the following day, with the flow reduced from 650 c.f.s. to 250 c.f.s., the count rose to 245 fish, Other high and low counts appear at random and apparently are independent of the flows tested around the bow. Nongame Fish Separating Device Large numbers of river-run, nongame fish have been taken with the adult salmon and steelhead at the Oxbow upstream trapping facility since operations began. This condition has tended to interfere with the efficiency of the trapping and hauling operation and occasionally has resulted in mortality to salmon and steelhead from smothering. Concentration of game with nongame species also may contribute to the transmission of disease. An investigation was made of possible ways to separate the salmon and steelhead from the other fish in the trap. For this purpose, varied combinations of experimental, perforated wooden plates were installed between the hopper and the brail sections of the trap. A plate with 2 1/2-inch diameter perforations_ proved to be the most effective in removing smaller nongame fish from the brail compartment (Figure 7), Adjustment of hole dimension may be necessary from year to year because of changes in fish size. With the plate in operating position, the smaller trash fish first enter the hopper through the perforation and the larger salmon and steelhead remain in the brail for later transfer to the transport truck without serious complication from the undesirable species. Although all of the trash fish are not separated from the salmon and steelhead by the use of this plate, large numbers are eliminated. On occasion, some resident game fish and small steelhead have moved through the plate.