Post on 18-Jan-2016
Streamflow Response to Climate:Why Geology Matters
– Tim Mayer, US Fish and Wildlife Service
Presented at the Oregon Water Conference
Corvallis, ORMay 24-25, 2011
Warmer temperatures, reduced snowpacks, earlier snowmelt and more winter rain v snow
will lead to:
Earlier timing of snowmelt runoff
Decreased summer/fall baseflows
Increased water temperatures
Increased winter flooding
Purpose of Study
To consider how climate change impacts to streams vary for different stream types, as defined by
elevation and geology.
Focus on the Pacific Northwest.
Crater Lake Nat ParkMt Rainier Nat Park
Olympic Nat Park
Surface-dominated and Groundwater-dominated Flow Regimes
River Type Elev Annual Pcp Annual Runoff (m) (cm/yr) (cm/yr)Little R, OR Surface Rain 860 156 89Salmon R, CA Surface Snowmelt 1300 141 83McCloud R, CA Groundwater 1500 143 87
Mean Daily Discharge 1960-1989 for Three Stream Types Rain Basin, Snowmelt Basin, and Groundwater Basin
Oct Dec Feb Apr Jun Aug Oct
Dis
char
ge
(mm
/day
)
0
2
4
6
8
10
Little R (rain) Salmon R (snowmelt)McCloud R (groundwater)
USGS Grid Map of Baseflow Index (Wolock, 2003)
Stream Types and Summer Streamflow
Contrast in summer flows in two Oregon rivers
Groundwater-dominated stream
Surface-dominated stream
Importance of Groundwater Basins (sub-watersheds) to Mainstem Flows on Three Major River Systems
Average Monthly Flow Upstream as a % of Downstream Flow for the Klamath R, the Umpqua R, and the Rogue R
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Flo
w %
0
20
40
60
80
100
KlamathUmpquaRogue
Predicted v Observed Low Flow (P10) for 281 OR StreamsMultiple Linear Regression
Predictors: Drainage area, Pcp, Longitude, (BFI)
-2 -1 0 1 2 3 4
Pre
dic
ted
Lo
g P
10
-2
-1
0
1
2
3
4
Observed Log P10
-2 -1 0 1 2 3 4
Pre
dic
ted
Lo
g P
10
-2
-1
0
1
2
3
4
no BFIr2 = 0.56
w/ BFIr2 = 0.86
Stream Types and Climate Change Impacts
Earlier timing of snowmelt runoff and decreased baseflows
Mayer and Naman (2011) compared trends in monthly and annual streamflows from 1956 to 2005 among
stream types. Examined 10 rain basins, 5 snowmelt basins, and
11 groundwater basins (all with minimal regulation and diversion).
Mayer and Naman (2011)
Rain Basins – large and variable trends in monthly flows in winter, very small trends in summer.
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep WY
Ch
ang
e in
Flo
w
(mm
/day
)
-3
-2
-1
0
1
210 Surface-dominated Rain Basins
Snowmelt Basins – little or no change in monthly flows in winter, increases in early spring, decreases in late spring, very small trends in summer.
Mayer and Naman (2011)
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep WY
Ch
ang
e in
Flo
w
(mm
/day
)
-3
-2
-1
0
1
25 Surface-dominated Snowmelt Basins
Groundwater Basins – more uniform trends (mostly declines) in all months, less of a decline or even increases at some sites in Mar/ Apr, relatively large declines in summer/fall flows in comparison to surface-dominated streams.
Mayer and Naman (2011)
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep WY
Ch
ang
e in
Flo
w
(mm
/day
)
-3
-2
-1
0
1
211 Groundwater-dominated Basins
“…absolute decreases in July-September baseflows are significantly greater, by an order of magnitude, in groundwater basins compared to surface-dominated basins…”
Mayer and Naman (2011)
Stream Types and Climate Change Impacts
Warmer Water Temperatures?
Groundwater-dominated stream
Surface-dominated stream
Relationship of Stream/Air Temperature Williamson River and Sprague River, OR 2007-2010
Weekly 7D Avg Air T Agency Lake, OR (C)
-10 -5 0 5 10 15 20 25
Wee
kly
7D A
vg S
trea
m T
(C
)
-10
-5
0
5
10
15
20
25Sprague R nr Chiloquin, OR BFI=0.79
Williamson R blw Sprague nr Chiloquin, ORBFI=0.90
Stream/Air Temperature Relationship
Relationship of Jul-Aug Stream/Air Temperature Williamson River and Sprague River, OR 2007-2010
Weekly 7D Avg Air T Agency Lake, OR (C)
8 12 16 20 24 28
Wee
kly
7D A
vg S
trea
m T
(C
)
8
12
16
20
24
28
Williamson R blw Sprague nr Chiloquin, ORBFI = 0.90
Sprague R nr Chiloquin, ORBFI = 0.79
y = 0.61x + 10.8
y = 0.39x + 7.94
Summer Stream/Air Temperature Relationship
7 Stream Temperature Sites In the North Umpqua and Upper Rogue
August Stream/Air Temperature Relationships
August Stream/Air Temperature Relationship 7 Stream Sites in the Umpqua and Rogue
Aug Weekly 7-D Average Air T (C)
5 10 15 20 25 30
Au
g W
eekl
y 7-
D A
vera
ge
Str
eam
T (
C)
5
10
15
20
25
30
August Stream/Air Temperature Relationships
August Stream/Air Temperature Relationship 7 Stream Sites in the Umpqua and Rogue
Aug Weekly 7-D Average Air T (C)
5 10 15 20 25 30
Au
g W
eekl
y 7-
D A
vera
ge
Str
eam
T (
C)
5
10
15
20
25
30
BFI = 0.42
BFI = 0.45
BFI = 0.53 BFI = 0.66
BFI = 0.81 BFI = 0.88
BFI = 0.68
Regression Results from August Stream/Air Temperature Relationships
Aug 7-D Avg Stream T/Air T v BFI 7 Stream Sites in the Rogue/Umpqua
BFI
0.0 0.2 0.4 0.6 0.8 1.0
Rat
io o
f A
ug
7-D
Str
eam
T/A
ir T
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
y = -1.01x + 1.43
r2 = 0.96
Regression Results from August Stream/Air Temperature Relationships
Aug 7-D Avg Stream T/Air T v BFI 14 Stream Sites in OR
BFI
0.0 0.2 0.4 0.6 0.8 1.0
Rat
io o
f A
ug
7-D
Str
eam
T/A
ir T
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Umpqua/Rogue sitesOther Misc OR sites
Regression Results from August Stream/Air Temperature Relationships
Slope of Linear Regression of Aug Stream to Air Temp 7 Stream Sites in the Rogue/Umpqua
BFI
0.0 0.2 0.4 0.6 0.8 1.0
Air
Tem
p C
oef
fici
ent
0.0
0.2
0.4
0.6
0.8
1.0
y = -0.58x + 0.80
r2 = 0.78
Regression Results from August Stream/Air Temperature Relationships
Slope of Linear Regression of Aug Stream to Air Temp 14 Stream Sites in OR
BFI
0.0 0.2 0.4 0.6 0.8 1.0
Air
Tem
p C
oef
fici
ent
0.0
0.2
0.4
0.6
0.8
1.0
Potential Climate Change Impacts to Groundwater-dominated Streams
Changes in timing and baseflows
– Groundwater basins show some indication of earlier timing of snowmelt runoff due to reduced snowpack but timing changes are more subtle and spread out. The effects of reduced snowpacks are extended into summer, resulting in larger absolute decreases in summer baseflows.
Potential Climate Change Impacts to Groundwater-dominated Streams
Warmer water temperatures
– Summer water temperatures are considerably cooler in groundwater-dominated streams and these systems may be less sensitive to increasing summer air temperatures than surface-dominated streams.
Questions?
Crater Lake Nat ParkMt Rainier Nat Park
Olympic Nat Park