Poor streamflow conditions in the Rogue River Basin have state fish managers asking to dig deeper than normal this year into stored Lost Creek Lake to stave off a potential die-off of Rogue chinook salmon susceptible to disease outreaks in low and hot summer flows.
The Oregon Department of Fish and Wildlife on Tuesday will ask the U.S. Army Corps of Engineers for an extra 50,000 acre-feet of stored Lost Creek Lake water be spilled judiciously this summer to help both spring and fall runs of Rogue chinook migrate safely to upstream spawning grounds.
That's above the 180,000 acre-feet of water already planned for Rogue fish enhancement, which joins winter flood control as the two primary purposes for operation of Lost Creek dam on the Rogue.
The extra water is to make up for the lack of natural stream flow into the Rogue, as well as flows so low into Lost Creek Lake that the Corps already has been drawing the reservoir down to help make the Lower Rogue Canyon's waters more cool and fish-friendly for migrating spring chinook.
Not spilling the extra water from the reservoir's regular "carryover" storage could trigger an outbreak of natural diseases that strike chinook, particularly the all-wild fall chinook run, when low water warms above 68 degrees in the lower Rogue at Agness, according to the ODFW.
"We're going to have to use some carryover water unless we want dead fish everywhere," ODFW fish biologist Pete Samarin says. "That most likely will be the case."
If done as expected, it will be only the fourth time in the reservoir's 38-year history that the ODFW has dipped into the carryover storage — stored water that forms the foundation for filling Southern Oregon's largest reservoir the following year.
In the previous three years — 1992, '94 and 2001— late fall and early winter rainfalls allowed the reservoir to recoup that previously spent water and fill as scheduled the following year, Corps records show.
The request comes after a new federal Natural Resources Conservation Service report shows the Rogue Basin runoff forecast is about 10 percent less than the already low April forecast.
The new forecast triggered the ODFW to redo its draft water-release plan for Lost Creek Lake, which heretofore was slightly above last year's flows at some summer intervals.
The draft release plan is now similar to last year, Samarin says.
Lost Creek Lake's stored water is released under plans biologists, hydrologists and others craft to help migrating spring chinook and fall chinook avoid outbreaks of diseases such as columnaris, a natural disease that spreads in warm water.
It attacks fish's gills and can trigger major die-offs in the Lower Rogue Canyon as salmon struggle to reach the cool upstream environs where they spawn in late summer and fall.
Before the reservoir supplemented summer Rogue flows, columnaris outbreaks were somewhat common and kept the basin's fall chinook numbers down.
Spilling more water than normal in summer now keeps the columnaris relatively in check, helping the basin's fall chinook population grow since the late 1970s. But outbreaks can still occur in drought years such as 1992, which killed off nearly 70 percent of the spring chinook run and triggered an upper Rogue emergency angling closure.
That year, the reservoir topped out at about 19 feet shy of full on May 1, the regular date the Corps shoots for to fill. This year, Lost Creek Lake's elevation peaked just under full, but low runoff into the reservoir meant releases were higher than in-flows as early as late April.
That has led to a quicker drop in the lake's elevation than most years, triggering the request for more water.
"At this point, we have to watch every drop," Samarin says. "The carryover will be necessary to get the fall fish through."