US Army Corps of Engineers

BUILDING STRONG®

Fall Creek Drawdown:Benefits and Impacts to Fish, Flows, and the Downstream EnvironmentGreg Taylor

Fisheries Biologist

Willamette / Rogue Projects

Within Our Reach

December 11th, 2012

BUILDING STRONG®

BUILDING STRONG®

OperationsMinimum conservation pool (728)

Dec-Jan

Refill Feb. – mid May

Drawdown Sept-Nov.

BUILDING STRONG®

BUILDING STRONG®

Fall Creek Drawdown Biological Objectives

Increased fish passage efficiency

Increased fish passage survival

Reduced predation and competition for rearing juvenile chinook salmon

BUILDING STRONG®

1-Sep

7-Sep

13-S

ep

19-S

ep

25-S

ep1-

Oct

7-Oct

13-O

ct

19-O

ct

25-O

ct

31-O

ct

6-Nov

12-N

ov

18-N

ov

24-N

ov

30-N

ov

6-Dec

12-D

ec

18-D

ec

24-D

ec

30-D

ec5-

Jan

11-J

an

17-J

an

23-J

an

29-J

an4-

Feb

10-F

eb

16-F

eb

22-F

eb

28-F

eb

670

690

710

730

750

770

790

810

830

2011/12 Drawdown

Minimum conservation pool

BUILDING STRONG®

BUILDING STRONG®

Upper ReservoirUpper Reservoir

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Sediment in Reservoir

BUILDING STRONG®

BUILDING STRONG®

RO Intake and Fish Horns

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BUILDING STRONG®

BUILDING STRONG®

BUILDING STRONG®

Gravel accumulation below dam

BUILDING STRONG®

Lower Fall Creek

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Confluence of Fall Creek andMiddle Fork Willamette River

BUILDING STRONG®

BUILDING STRONG®

09/15/11 09/29/11 10/13/11 10/27/11 11/10/11 11/24/11 12/08/11 12/22/11 01/05/12670

690

710

730

750

770

790

810

830

0

20

40

60

80

100

120

140

160

180

Chinook Migration Timing vs ElevationR

es

erv

oir

Ele

va

tio

n (

fee

t)

Ch

ino

ok

Co

un

t

Trap Off

Min. Con. Pool (728’)

BUILDING STRONG®

Summary Reservoir drawdown increased fish passage efficiency, survival, and reduce

predation and competition for juvenile chinook salmon rearing in the reservoir

Physically reconnect the river above and below the dams

Large Quantity of sediment released downstream during drawdown► Sediment is silt, sand, and gravel► Helps replenish sediment downstream of dams which may contribute to ecosystem health (salmon

spawning in newly deposited gravel).

Obstacles to implementing further drawdowns:

► 1) Impacts to downstream users and the environment • Environmental compliance

► 2) Impacts to other USACE authorized purposes