Absolutely. At every stage of a salmonid's life history, the mortality changes when natural/environmental factors change. It is part of the selective process that has made the populations what they are in tens of thousands of generations. Will ALL eggs be crushed or washed away? It is highly unlikely at the current discharge level. The system has gone through harsher condition than this. The optimistic view would be that with a post-season estimate of over 20 million pink salmon return this season, the amount of eggs that survive through this winter will most likely be above satisfactory level.
Beside human factors, one should remember that the return of spawning adult salmon highly depend on the environmental condition. If the overwintering river condition is good, spring predation is low during juvenile rearing, sufficient amount of food is present in the estuaries during smoltification, predation by warm water species is absent during juvenile outmigration, predation during adult years is low, then one may just see a good salmon return. In the real world, these favourable conditions almost never coincide with each other.