128 



Adverse EfTects on Adult SaLmonids 



Past research has shown that high spill at dams may lead to confusing tailwater 

 currents that make it difficult for adults to find fishway entrances. Generally speaking, adult 

 fish passage facilities were engineered on the assumption that a substantial portion of the 

 flow would go through turbines. When spillway fiows exceeded turbine flows at the Snake 

 River dams in the 1960s and 1970s, adverse tailwater currents and delays of adult migrants 

 were observed. Junge (1966); Junge (1971). 



If the proposed spill levels recommended by NMFS are implemented, confusing 

 tailwater currents may occur, with accompanying delays of migrating adults. Moreover, 

 according to NMFS, spilling at the levels proposed will create gas supcrsaturation in the 

 spillway side of the dain as high as 120% (12 hour average) and 125% (two hour maximum). 

 (Biological Opinion at 106.) Adults exposed to these levels for extended periods of time are 

 likely to suffer gas bubble disease. 



For example, in 1968, when excess water was spilled at John Day, adults were 

 delayed for several days and a substantial mortality of chinook and sockeye was recorded. 

 The State of Oregon estimated that over 20,000 adult chinook were lost. Beiningen and Ebel 

 (1970). Meekin and Allen (1974) estimated that 6% to 60% of adult salmonids in the middle 

 region of the Columbia River died between 1965 and 1970; carcasses of adult salmon were 

 found in the river when gas supcrsaturation reached 120% or higher. 



The spill recommended by NMFS would occur from April through August. 

 Endangered Snake River spring/summer chinook adult salmon will be returning during this 

 period of time to pass upstream. NMFS spill plan will expose these adults to elevated gas 

 levels during their entire migration past the eight mainstem dams, but also delay. that 

 migration. Since adult salmon have finite energy reserves, delay in their migration will tend 

 to decrease survival in addition toany survival decrease resulting from gas bubble disease. 



I note that when the United States Fish and Wildlife Service made its request to 

 increase TDG, they asserted that a cap of 115% measured at the Camas/Washougal 

 monitoring station would equate to approximately 125% TDG in the stilling basin. NMFS 

 appears to assume that measurement of 115% at Camas Washougal will equate to levels of 

 only 120% in the stilling basin. Before embarking on a spill program of this magnitude, it 

 would seem appropriate to understand what levels of TDG will in fact result in stilling basins 

 at given downstream TDG levels. 



NMFS proposes to measure TDG at the Camas/Washougal monitoring station. The 

 Camas/Washougal station has consistently the lowest TDG measurements at the first three 

 monitoring stations downstream from Bonneville Dam: Warrendale, Skamania, and 

 Camas/Washougal. Bonneville Dam is structured with the first powerhouse on the Oregon 

 side, a man-made island, a spillway in the middle, another man-made island, and the second 

 powerhouse on the Washington side. The second powerhouse is used last, so that most flow 

 will pass through the first powerhouse and the spillway. These flows mix slowly as they 



