I think that is because of water coming from Dworshak. I my opinion you need to have sufficient water for fish migration. It seems to many that if the Lower Snake Dams were removed that no more flow augmentation would be necessary. This is certainly my hope as well as Idaho irrigators. A reservoir is a water storage bank to allow for this.
Lets look at some of the most obvious.
Predators, overharvesting, a protected ocean habitat, elimination of nets. I agree Tom, that the 13 agribusinesses should continue to receive water from the Snake for Irrigation. I do not think that is in any one's interest to negatively impact anyone that is benefiting from the current system. I guess the thing here Tom, is that keeping the dams would impact many other industries that would be much more difficult to mitigate the effects of. The salmon decline parallels the commercial fishing, The first thing that happens is that to offset commercial fishing is the introduction of hatcheries.