Challenges for the Colorado River BasinOctober 16, 2013

Doug Kenney, Ph.D.Director, Western Water Policy ProgramUniversity of Colorado Law SchoolDouglas.kenney@colorado.edu

Jeff LukasSenior Research Associate,Western Water AssessmentCIRES, University of ColoradoLukas@colorado.edu

1www.learnmoreaboutclimate.org www.cires.colorado.ed

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Organized by: Anne Gold, Ph.D. CIRES and Deb Morrison, CU Boulder School of EducationProduced by: Kit Seeborg for Learn More About Climate

Climate Change & Water in the West

Webinar Facilitators

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Deb MorrisonPh.D. Candidate

CU Boulder, School of Education

Margi DashevskyCU Boulder

Anne Gold, Ph.D.CIRES, Education & Outreach

Kit SeeborgLearnMoreAboutClimate.org

Water in the West Webinar SeriesOverall Structure

◦Two webinars◦Background reading material on the

website

Requirements For Credit

More Webinar Series to come◦Extreme Weather in Spring 2014

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Major rivers of the U.S.

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1,450 miles long

Basin covers 246, 000 sq. mi.

Headwaters in high mountains of CO, WY, UT, NM

Colorado River

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A highly developed (and overworked) river

Covers 7 states and 2 countries (and 22 Indian reservations)

Water supply for 40 million people

Irrigation water for 5.5 million acres

Generates 4,200 megawatts of hydropower

Home to 11 National Parks

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Nearly all runoff comes from the cool and wet mountain headwaters above 8,000’

Precipitation Runoff

mm mm

0” 20” 40” 0” 6” 12”8

Snowmelt-dominated hydrology:~80% of annual flow comes April 15-July15Gaged daily flow, Colorado River at Lees Ferry, 1950-1955

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Colorado River Compact of 1922 (and the Law of the River)Total Allocation of 16.5

MAF7.5 MAF to the Lower

Basin ◦ 4.4 MAF to California◦ 2.8 MAF to Arizona◦ 0.3 MAF to Nevada◦ Doesn’t include LB

tributaries7.5 MAF to the Upper

Basin◦ 51.75% to Colorado◦ 23% to Utah◦ 14% to Wyoming◦ 11.25% to New Mexico

1.5 MAF to Mexico

Design of formula requires Upper Basin to release 7.5 MAF downstream each year for the Lower Basin.

Allocations to tribes taken out of state allocations where the reservation is located

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“A river no more”

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Data: Reclamation (1906-2010); 2011-13 values estimated from preliminary Reclamation data or projections

0

5

10

15

20

25

30

1900 1910 1920

Wat

er Y

ear F

low

, MAF

Naturalized streamflow, Colorado River at Lees Ferry, 1906-1922

The 1922 Compact assumed more runoff than has been available since then

Assumption: 16-17 million acre-feet on average based on ~20 years of data

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Naturalized streamflow, Colorado River at Lees Ferry, 1906-2013

0

5

10

15

20

25

30

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Wat

er Y

ear F

low

, MAF

Data: Reclamation (1906-2010); 2011-13 values estimated from preliminary Reclamation data or projections

Reality: 14.9 million acre-feet on average

The 1922 Compact assumed more runoff than has been available since then

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Tree rings tell us the early 1900s was one of the wettest periods of the last 1200 years

101112

13141516

1718

750 1000 1250 1500 1750 2000

Water Year

Ann

ual F

low

, MA

F

Tree-ring reconstruction of Colorado River at Lees Ferry streamflow from 762-2005, with 20-year running mean

Gaged period

Reference: Meko et al. 2007, Medieval Drought in the Colorado River Basin, Geophysical Research LettersData: TreeFlow: http://treeflow.info/upco/coloradoleesmeko.html

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UT

WY

NM

AZ

NV

CA

Allocations at 15 versus 16.5 MAF*

CO

Mexico

Mexican apportionment and delivery to Lower Basin are generally considered the first two priorities on the river

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Photo provided by Jennifer Pitt

No flow to the Colorado River delta in most years since Glen Canyon Dam built (1963)

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The Colorado River’s endangered native fish

Evolved with warm, muddy water conditionsNeed off-channel “backwater” habitat for

raising young

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Glen Canyon Dam and Lake Powell

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Sediment is now trapped behind dams, so downstream water is clear

1963:Glen Canyon Dam built

Sediment in Grand Canyon decreases >95%

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Dams release water from lower levels of reservoir: cold water, less seasonal change

1973Lake Powell nearly full

Water Temperature, Colorado R. at Lees Ferry, 1960-2000

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1963:Glen Canyon Dam built

Dams cut off the annual peak flows needed to maintain backwater habitat

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Naturalized streamflow, Colorado River at Lees Ferry, 1906-2013

Data: Reclamation (1906-2010); 2011-13 values estimated from preliminary Reclamation data or projections

Since 2000, Colorado River flows have been very low overall

0

5

10

15

20

25

30

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Wat

er Y

ear F

low

, MAF

14.9 million acre-feet long-term average

12.3 million acre-feet average, 2000-2013

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Causes of low flows since 2000Main cause: Below-average

precipitation – likely natural variability

Contributing: Above-average temperatures – likely due to anthropogenic climate change

Future: Climate models uncertain about precipitation change, but high confidence in further warming

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Data: Reclamation (1906-2010); 2011-13 values estimated from preliminary Reclamation data or projections

0

5

10

15

20

25

30

1950 2000 2050 2100

Annu

al R

unoff

, MAF

Climate models: decreasing flow likely in the Colorado River over the 21st century

13.0 million acre-feet average, 2035-2064

Median of 39 climate model runs, mid-emissions scenario

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Demands have caught up with supply

192319331943195319631973198319932003201320232033204320530

5000

10000

15000

20000

25000

Total Supply (10-yr running average at Imperial Dam)

Total Demand (10-yr running average)

Year

Volu

me

(MAF

)

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Emergence of the “bathtub rings”

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Framing of the Study

Development of Water Supply Scenarios

Development of Water Demand Scenarios

Identification of System Reliability Metrics

Identification and Characterization of Options

Development of Portfolios of Options

Evaluation of System Reliability without Options and Strategies

Characterization of System Vulnerabilities

Evaluation of System Reliability with Options and Strategies

Summary of Findings and Future Considerations

Plan of Study

Technical Report(TR) – A

TR – F

TR – B

Study Report

TR – C TR – D

TR – E

TR – G

Colorado River Basin Supply and Demand Study

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Basin Study: 4 water supply scenarios, using gaged flows, tree-ring flows, and projected flows

1) Gaged Flows

2) Tree-ring Flows3) Tree-ring Flows blended with Gaged

4) Projected Flows

Less water supply

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A wealth of possible solutions

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0

5

10

15

20

25

30

1950 2000 2050 2100

Annu

al R

unoff

, MAF

Uncertainty in future water supply: differences among GCM runs

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0

5

10

15

20

25

30

1950 2000 2050 2100

Annu

al R

unoff

, MAF

Uncertainty in future water supply: differences among GCM runs

Most runs show decreasing flow in 21st century, but some show increasing flow

We know that high variability will continue

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Source: Reclamation – Basin Study Interim Report No. 1 (2011)

Observed Projected (2011-2060)

Less uncertainty about timing of runoff: warming will shift the peak earlier

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Water withdrawals for electricity production

Kenny et al. 2009 37

Planning for an uncertain future

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Understanding choices and trade-offs

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Change is:Ever-present is human and natural

systemsA challenge for planning and

managementAn opportunity to do things differently

in the future

0

5

10

15

20

25

30

1950 2000 2050 2100

Annu

al R

unoff

, MAF

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Watch this webinar’s video replay:

http://www.learnmoreaboutclimate.org

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