During 2006, we used acoustic telemetry and a route-specific survival model (RSSM, Skalski et al. 2002) to estimate behavior, passage, and survival of juvenile salmonids during two different spill operations and diel periods at McNary Dam. An evaluation of 12-h versus 24-h spill was proposed for the spring migration period at McNary Dam. However, high river discharge did not allow for the 12-h spill treatment, and thus, resource managers decided on testing two 24-h spill treatments having two distinct spill patterns. The first treatment, the “Fish Passage Plan” (FPP) treatment emphasized spill on the north end (bays 1-3) of the spillway and generally higher discharge through the north powerhouse. The second treatment, the “Test Spill” (TS) treatment emphasized spill on the south end (bays 18-20) of the spillway and relatively less discharge through the north powerhouse. During the summer, two dam operations were evaluated: 1) 24-h spill at 60% of total river discharge, and 2) 24-h spill at 40% of total river discharge. Both the Fish Passage Plan treatment in spring and the 40% spill treatment in summer had the more distinct pattern in powerhouse operations over the 24-h diel cycle, with generally higher powerhouse discharge and lower spill discharge during daytime hours (about 0600 to 1800 hours) compared to the alternative spill treatment.
