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