Drought Impacts to Bull Trout in the Yakima Basin – 2001 (2005?)

John Easterbrooks, Region 3 Fish Program Manager

• “Adfluvial” (lake dwelling, stream spawning) bull trout populations in three Yakima Basin irrigation storage reservoirs (Keechelus, Kachess, and Rimrock) were affected by the severe drought of 2001. Similar conditions are anticipated in 2005.

• Blocked upstream passage into spawning tributaries in late summer as the reservoirs are drained is the primary impact. Lower stream flows in 2005 may cause passage problems to occur earlier in the summer, depending on the rate of reservoir drawdown.

• Corrective actions were implemented at Kachess and Rimrock reservoirs in 2001 to improve passage conditions for mature adults to prevent loss of a year class of juvenile production.

Gold Creek – Keechelus Reservoir(headwaters of the Yakima River near

Snoqualmie Pass)

(no remedial action because of upstream flow problems)

Lower Gold Cr. and Keechelus Reservoir

Alluvial Fan at Mouth of Gold Cr.

Gold Cr. Impassable Conditions

Gold Creek – July 20

August 1 August 15

Box Canyon Creek – Kachess Reservoir

Overview of channel modification on Kachess Reservoir lake bed

Construction of passage flume

Straw bale, T-post &Plastic Sheet FlumeDesign

Lower end of BoxCanyon Cr. bull troutpassage flume

Passage flume lookingupstream

Finished flume with rockweirs to create a series of pools

Mouth of Box Canyon Cr. flume and Kachess Reservoir

First weir at mouth of flume and attraction flow

Adult bull trout in Box Canyon Cr. passage flume

Box Canyon flume after fall rains

Indian Creek – Rimrock Reservoir

(upper Tieton River basin near White Pass; tributary to the Naches River)

Multiple channels at mouth of Indian Cr.

Plastic and straw bale wing dam flow diverter

Indian Cr. with flow diverter (left) and N.F. Tieton River (right)

After fall rains in October, 2001

After fall rains in October, 2001

South Fork Tieton R. – Rimrock Reservoir

Barrier waterfall develops when reservoirstorage content drops below 127,000 acre-feet. USBR attempts to operate reservoir to stay above that level through Aug. 12 to provide bull trout passage. Late in the season, the falls and shallow, multiple channels across the lake bed presents a hazard to post-spawn adults returning to the lake.

S.F. Tieton Falls, height = 10 meters, reservoir content 48,000 acre-feet

S.F. Tieton R. below falls across Rimrock Reservoir lake bed

Mouth of S.F. Tieton R. and Rimrock Reservoir at 48,000 ac-ft.