Forced by a federal court decision to develop a way to manage water
that would help Yakima River spring chinook recover, fish biologists
invented the system called "flip-flop," which alternates flows in the
Yakima and Naches rivers to serve both farming and fish. And for a
while, it seemed to work: Farmers got their water in the key
late-summer and early-fall dry periods, and the spring chinook
rebounded, albeit modestly.

Unfortunately the strategy had a negative impact on native steelhead and new research suggests the flip-flop may also take an unexpected toll on the Yakima spring chinook, the very fish it was designed to protect. 

Via: High Country News  LINK