i'm not intimately familiar with washington's water rights administration except that i know they run prior appropriation. how strict their prior appropriation is and whether or not the state/district courts or the state agency adjudicates the rights i don't know
but i can see this turning into a big court battle between state rights as it pertains to adjudicated water rights protected by a state constitution and federal overreach that injures those water rights. a fight that would be hard to win for the feds i think. at least, if this proposal doesn't properly compensate water users, which it claims to i guess.
but even so, sometimes the only way to compensate a water user is with water, not money. it's very dangerous path to try and walk when you threaten water rights, and i do root for water rights, after all they are usually codified and called rights for a reason
that said i'm certainly rooting for the salmon, but when it comes to water rights it's hard to see anything stopping the lobbing of grenades