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
BUILDING STRONG®
Sediment in Reservoir
BUILDING STRONG®
BUILDING STRONG®
RO Intake and Fish Horns
BUILDING STRONG®
BUILDING STRONG®
BUILDING STRONG®
BUILDING STRONG®
Gravel accumulation below dam
BUILDING STRONG®
Lower Fall Creek
BUILDING STRONG®
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
Top Related