An Upper Basin Scientific Perspective on the Colorado River water supply in the 21st Century

31st Colorado Water WorkshopPanel: Is the Colorado River a Developed Resource?July 28, 2006Gunnison, CO

Brad UdallDirector CU-NOAA Western Water AssessmentBradley.Udall@colorado.eduwwa.colorado.edu

Overview

• Western Water Assessment

• Overview of Upper Colorado Compact

• Climate Change Studies in the West and Basin

• Lessons from Paleoclimate Studies

• The Water – Energy Nexus

• What Does all this mean?

Time for some new thinking…

Western Water Assessment one of 8 Similar NOAA Regional Integrated Sciences and Assessments (“RISA”) Programs.

http://www.climate.noaa.gov/cpo_pa/risa/

• One Recent WWA Product

Climate OverviewPaleoclimate OverviewSeasonal Forecasting AccuracyRiver Forecast Center MethodsClimate Change

In conjunction with California Department of Water Resources

http://watersupplyconditions.water.ca.gov/co_nov05.pdf

Covers CO, UT, WYFeature ArticlesTemperature Past MonthPrecipitation Past MonthUS Drought MonitorReservoir StatusColorado Water AvailabilityTemp OutlookPrecipitation OutlooksEl Nino Status

Thanks to: NOAA, State Engineers, NRCS,

WWA New Product –

Intermountain West Climate

Outlook

Available at: Wwa.colorado.edu

Upper Basin Compact Allocation -1

• Article III– 51.75% to Colorado– 11.25% to New Mexico– 23% to Utah– 14% to Wyoming– Plus 50,000 af to AZ – III(b)(3) States Allowed to Exceed Apportionments

unless so doing deprives another state of its allocation

• Article VIII– Creates Upper Colorado River Compact Commission

Upper Basin Consumptive Use

0

1000

2000

3000

4000

5000

6000

197119

7219

7319

7419

7519

7619

7719

7819

7919

8019

8119

8219

8319

8419

8519

8619

8719

8819

8919

9019

9119

9219

9319

9419

9519

9619

9719

9819

9920

00

Year

AF

x 1

00

0

Annual Water Consumed

Linear (Annual Water Consumed)

Source: Consumptive Uses and Losses Report - USDOI

Source: Kuhn, CRWCD

Total Colorado Consumptive Use

0

500

1000

1500

2000

2500

3000

197119

7219

7319

7419

7519

7619

7719

7819

7919

8019

8119

8219

8319

8419

8519

8619

8719

8819

8919

9019

9119

9219

9319

9419

9519

9619

9719

9819

9920

00

Year

AF

x 1

00

0

Annual Water Consumed

Linear (Annual Water Consumed)

Source: Consumptive Uses and Losses Report - USDOI

Source: Kuhn, CRWCD

How Much Developable UB Water?

• Conventional Analysis– Depends on Hydrology and Mexican Issue

• Do UB have a year-in, year-out Mexico delivery requirement or is there a surplus above III(a+b) sometimes considering LB tributaries?

• What are the ten worst hydrologic years you want to include?– Some Numbers

• ‘ Noah’s Determination’ = 7.5 maf UB, CO=3.9maf (assumes no Mexico requirement)

• 1988 Hydrologic Determination = 6 maf, CO=3.1 maf (assumes UB Mexico requirement of 750kaf/yr)

• T-K 1965 study = 5maf, CO=2.7 maf

• Unconventional Analysis– There is no ‘one’ number – how often, and how much shortage

is acceptable?

Source: Kuhn

The Changing Climate of

Climate Change…

“The proper response to uncertainty is insurance, not denial” ~ Anonymous

Ancient(?) History – 1997 AWWA Journal

Bulletin of American

Meterological Society,

January 2005

Declining Snowpack

from 1950 to 1997 in large parts of the

West

Source: Mote, et al.

A Warming West from

1950 to 1997…

Source: Mote, et al.

Precipitation – Mixed Bag from 1950 to

1997

Source: Mote, et al.

Declining Snowpack Summary

• Widespread Declines in SWE in West during 1950-97• Spatial Consistency, Elevational Dependence, Model

Agreement all point to climate as cause.• Increases in temperature are consistent with rising ghg

and will almost certainly continue.• Likely that losses in snowpack will continue and even

accelerate with highest losses in milder climates and slowest losses in high peaks of northern Rockies and Southern Sierra.

Source: Mote, et al.

Easterling, BAMS, 2002

WWA and Colorado Climate Center Colorado Temperature Trend Study• Klaus Wolter and Nolan Doesken

• 70 to 110 Year Datasets Possible only in a few limited areas

• Max, Min, Growing Season Length, Cold Snaps, Heat Waves

• Preliminary Results: Spring Time Warming Trend ‘Most Dominant and Reliable’

• Full Results this Fall

Colorado River Climate Change Studies over the Years

• Revelle and Waggoner, 1983

• Gleick, 1988

• Nash and Gleick, 1991

• Nash and Gleick, 1993

• Gleick and Chalecki, 1999

• Christensen, 2004

Lessons from Studies

• Consistent agreement that it will get warmer, and likely much warmer than global average increases

• Earlier snowmelt, increased ET very likely• More variability in runoff • Precipitation uncertain, but warming appears to

trump any precipitation increases• Caveat: models are still limited in their ability to

reproduce regional climates and these studies are not predictions

Man Bites Dog: How Does Water Use Affect Climate?

• Energy Used to Pump, Pressurize, Treat, Heat Water

• In California Water Use Consumes– 20% of all electricity– 30% of all natural gas, – Diesel for 120,000 cars/year

• Saving Water Saves Lots of Energy• Consider: carbon caps likely at least on electric

power production• Increased Price will reduce demand, other

feedbacks possible.

California Energy Commission, 2005

Inland Empire Utility Agency Energy Intensity (kwh/af)

IEUA Website, 2005

400 kwh/af

3200 kwh/af

New Lee Ferry Streamflow Reconstruction

• Woodhouse, Gray, Meko Study WRR• Added 40+ gage and tree-ring calibration years

relative to Stockton and Jacoby• 15.2 maf USBR Average Natural Flows• 14.3 to 14.7 maf this reconstruction• 13.5 maf S&J 1975 reconstruction• One 5-year period worse than 2000-2004, but eight

other periods may have been as dry.

Lees Ferry Reconstruction, 1536-19975-Year Running Mean

Assessing the 1999-2004 drought in a multi-century context

Source: Woodhouse

Source: Woodhouse

8 Periods may be worse than 2000-2004

Woodhouse, Meko, Gray New Reconstruction of Lees Ferry Streamflow, 20-year moving average, 1536-1997

Dry periods

Lowest 20-yr avg. Lowest 25-yr avg

1573-1592 (1) 1622-1646 (1)

1622-1641 (3) 1623-1647 (2)

1870-1889 (4) 1878-1902 (3)

1953-1972 (35) 1953-1977 (28)

Pluvial (Wet) periods

Highest 20-yr avg. Highest 25-yr avg.

1602-1621 (1) 1905-1929 (1)

1601-1620 (2) 1906-1930 (2)

1905-1924 (6) 1594-1618 (3)

Source: Woodhouse

Source: Woodhouse

Mixing Paleoclimate and Climate Change

• Trees are not a forecast – climate drivers in the future are likely to be different from the past

• But Trees are not worthless…– Variability in the tree-ring record is real, very large,

and at least some of the ancient droughts would likely stress current water management practices

– Historical record shows much more limited variability– As a planning exercise, using the tree-ring generated

streamflows with all their variability should provide valuable insights into system vulnerabilities

Concluding Thoughts• Many Signs – data & models – point to the possibility of

reduced runoff in the basin, even with slightly increased precipitation.

• Hence, additional development in the Upper Basin may have lower than expected yields if based on historical hydrology

• Were the past to repeat, there are some extended periods where water managers would be quite challenged – the natural variability in the basin is quite large!

• Development is ultimately a political question not a scientific one. However given the known decadal variability, “is there more water to develop?” is the wrong question. A better question is “how often and what size shortages are acceptable?”