Spill muddies Big Butte Creek

Biologists fear millions of spring chinook salmon eggs recently laid in the upper Rogue River might die in the wake of Sunday's breach of an earthen irrigation ditch that sent muddy, clay-laced water spewing into Big Butte Creek.

A nearly 100-foot piece of a main Eagle Point Irrigation Ditch failed early Sunday morning, sending a surge of water chugging down a clay hillside and across Cobleigh Road before reaching Big Butte Creek, a major upper Rogue tributary.

Lower Big Butte Creek and the portion of the Rogue downstream of its mouth represent the vast majority of the Rogue Basin's wild spring chinook spawning grounds, where most of the wild run recently has spawned in gravel egg nests called redds.

The fear is that the clay particles settled out and cloaked the redds, choking off water flow to the eggs and killing them, said Dan VanDyke, the Oregon Department of Fish and Wildlife's Rogue District fish biologist.

"It's very bad timing, a very bad location and potentially very bad geology," VanDyke said Monday.

The best-case scenario, however, was the clay remained suspended in the water and continued down the Rogue and away from chinook spawning gravels without sifting out, VanDyke said.

"There's justifiable reason for concern," he said.

ODFW crews will spend the next few days surveying the spawning grounds to determine what, if any, egg loss has occurred, ODFW biologist Jay Doino said Monday.

The cause of the failure was still unknown. EPID uses this stretch of canal to transfer about 86 cubic feet per second of Big Butte Creek water to irrigators, said Hazel Brown, the former EPID manager who is now a district adviser.

"The mountain just slid off," Brown said.

Brown said the stretch of canal, which diverts Big Butte Creek water, had not shown signs of leaking. The breach was reported about 5:30 a.m., and flows into the canal were blocked within an hour, she said.

Crews were working on repairs Monday, Brown said.

The ODFW, Oregon State Police and state Department of Environmental Quality were investigating the case, VanDyke said.

A U.S. Geological Survey gauge at Dodge Bridge, where Highway 234 crosses the Rogue near Eagle Point, shows a Sunday afternoon turbidity spike of about 20 times the amount registered immediately before the spike.

Wild spring chinook — especially early-run wild spring chinook — have been a depressed stock of Rogue salmon in recent years, with the placement and operation of Lost Creek dam considered the main factor. The dam blocked one-third of the wild spring chinook spawning habitat and warm winter flows from Lost Creek Lake alter spring chinook's natural egg-hatching cycle.

Mass losses of a single year's spawning run of Rogue spring chinook have occurred during heavy floods.

Chinook have a built-in mechanism for dealing with one-year spawning losses. Chinook born on any given year come back to spawn over a four-year span, so spring chinook spawning in any given year are progeny from several years' spawns.

The popular Rogue fishery on spring chinook consists of a mix of wild and hatchery-bred spring chinook.

Reach reporter Mark Freeman at 541-776-4470, or email at mfreeman@mailtribune.com.