Impacts of Climate Change on the Tualatin River Basin

Nathan VanRheenen, Erin Clancy,

Richard Palmer, PhD, PE

Dept. of Civil and Environmental EngineeringUniversity of Washington

www.tag.washington.edu

Talk Overview

Background

Research Approach

Impacts on Meteorology

Impacts on Hydrology

Impacts on System Yield

Final Conclusions

Insight from a Notable American Philosopher

The future ain't what it used to be.

-Yogi Berra

It's time for those of us who work on climate change to help the public and policymakers understand the evidence: Climate change is real, well underway, and poses severe risks to the United States and the world.

Dr. Peter GleickDirector, The Pacific Institute 2003 MacArthur Fellowship Award Winner

Translating the Challenge to Regional Analysis

What are the likely impacts of climate change on regional watersheds?

Types of impacts Magnitude of impacts Mitigation responses Case Studies

Seattle Water Department Portland Water Bureau Tualatin Basin

Setting

Rain-driven watershed (no snow impacts)

Multiple uses: M&I, Ag, Fish, Recreation 500,000 customers (M&I) Agriculturally productive Water Quality Concerns (temperature)

Current system is fully allocated M&I demands expected to increase 400% by 2050 Ag demands, 50% by 2050

System highly sensitive to changes in summer flows

System expansion is under consideration

Models for Evaluating Climate Change

General Circulation Models

Tualatin River Integrated Management System (TRIMS)

Hydrology Model, EPA BASINS

Tualatin River Integrated Management System (TRIMS)

Impacts on Meteorology

•Global climate models operate at a scale of 2-5° latitude

•Global data must be downscaled to the local station scale in order to assess the impacts of climate change on water resources.

Historical Meteorology

Hydrology Model

Climate Signals

PredictedMeteorology

From Climate Signals to Runoff

PredictedRunoff

Temperature Signals from GCMs

0

1

2

3

4

5

6

7

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

Month

Te

mp

era

ture

In

cre

as

e (

F)

2000

2020

2040

2060

-30%

-20%

-10%

0%

10%

20%

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

Month

Cha

nge

in P

reci

pita

tion

2000

2020

2040

2060

Precipitation Signals from GCMs

Impacts on Hydrology

EPA BASINS Watershed and subwatershed delineation:

ArcGIS add-on Rainfall-runoff simulation: HSPF (Stanford

Watershed Model) Can be extended to model water quality

Calibrated to match monthly flows at six stations

Hydrology Model

BASINS Model Nodes

0

50

100

150

200

250

300

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Av

era

ge

Flo

w (

cfs

)

2000 (modeled)

2020

2040

2060

Impacts on Hydrology: Hagg Lake Inflows

Flows at Mouth of Dairy Creek (July-October)

127 125

114

105

90

100

110

120

130

2000(modeled)

2020 2040 2060

Climate

Ave

rag

e F

low

(cf

s)

Impacts on Hydrology: Summer Flows

Impacts on Water Resources System

Tualatin River Integrated Management System (TRIMS)

TRIMS Description

Dynamic model of the basin Purpose: Calculate system yield Incorporates

Major system features and operations BASINS inflows M&I and Ag water supply demands

Present, Contracted, 2050 CWS environmental targets (Present, 2050) Instream flow targets Scoggins Dam expansion alternatives

Increase dam elevation by 20 ft, 40 ft

Hagg Lake Storage – Current System

Hagg Lake Storage – 40 ft Expansion

Hagg Lake Yield – Current System

30,000

35,000

40,000

45,000

50,000

2000 2020 2040 2060

Saf

e Y

ield

(ac

re-f

eet)

98% Reliable Yield 97% Reliable Yield

95% Reliable Yield 90% Reliable Yield

40000 acre-ft/100 days = 130mgd40000 acre-ft/150 days = 87 mgd

Hagg Lake Yield – Current System

24,000

26,000

28,000

30,000

32,000

34,000

36,000

38,000

40,000

2000 2020 2040 2060

97%

Rel

iab

le S

afe

Yie

ld (

acre

-fee

t)

Current Demands Contracted Demands 2050 Demands

Hagg Lake Yield – 20 ft Expansion

54,000

55,000

56,000

57,000

58,000

59,000

60,000

2000 2020 2040 2060

97%

Rel

iab

le S

afe

Yie

ld (

acre

-fee

t)

Current Demands Contracted Demands 2050 Demands

Hagg Lake Yield – 40 ft Expansion

70,000

71,000

72,000

73,000

74,000

75,000

2000 2020 2040 2060

97%

Rel

iab

le S

afe

Yie

ld (

acre

-fee

t)

Current Demands Contracted Demands 2050 Demands

Hagg Lake “Expansion Schedule”

25000

30000

35000

40000

45000

50000

55000

60000

65000

70000

75000

2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060

Sa

fe Y

ield

, 97

% R

elia

ble

(a

cre

-fe

et)

Current, 2000 climate 20 ft raise, 2000 climate 40 ft raise, 2000 climate

Current, 2060 climate 20 ft raise, 2060 climate 40 ft raise, 2060 climate

Projected Demand Curve, 2000-2060

Conclusion

Conclusion

Impacts on Temperature and Precipitation

Increase in temperature of 2-4 °F Wetter winters, drier summers

Impacts on Streamflow 10-20% lower flows in summer, wetter

winters Impacts on Yield

Decreases 1.5% per decade for current system and current demands

Conclusion

System Expansion without climate change

97% reliable yield increased from 38,000 acre-ft per year to 60,000 acre-ft (20-ft expansion) and 73,000 acre-ft (40-ft expansion)

System Expansion with climate change by 2040

Yield shifts downward by about 4,000 acre-ft

Climate change impacts suggest expansion needed 5-8 years earlier