Transcript Udall - Western State Colorado University

An Upper Basin Scientific Perspective on
the Colorado River water supply in the
21st Century
31st Colorado Water Workshop
Panel: Is the Colorado River a Developed Resource?
July 28, 2006
Gunnison, CO
Brad Udall
Director
CU-NOAA Western Water Assessment
[email protected]
wwa.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 Overview
Paleoclimate Overview
Seasonal Forecasting Accuracy
River Forecast Center Methods
Climate Change
In conjunction with California
Department of Water
Resources
http://watersupplyconditions.water.
ca.gov/co_nov05.pdf
WWA New
Product –
Intermountain
West Climate
Outlook
Covers CO, UT, WY
Feature Articles
Temperature Past Month
Precipitation Past Month
US Drought Monitor
Reservoir Status
Colorado Water Availability
Temp Outlook
Precipitation Outlooks
El Nino Status
Thanks to: NOAA, State
Engineers, NRCS,
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
Source: Consumptive Uses and Losses Report - USDOI
6000
4000
3000
2000
1000
Annual Water Consumed
Linear (Annual Water Consumed)
Source: Kuhn, CRWCD
0
19
7
19 1
7
19 2
7
19 3
7
19 4
7
19 5
7
19 6
7
19 7
7
19 8
7
19 9
8
19 0
8
19 1
8
19 2
8
19 3
8
19 4
8
19 5
8
19 6
8
19 7
8
19 8
8
19 9
9
19 0
9
19 1
9
19 2
9
19 3
1994
9
19 5
9
19 6
1997
9
19 8
9
20 9
00
AF x 1000
5000
Year
Total Colorado Consumptive Use
Source: Consumptive Uses and Losses Report - USDOI
3000
2000
1500
1000
Annual Water Consumed
Linear (Annual Water Consumed)
500
Source: Kuhn, CRWCD
0
19
7
19 1
7
19 2
7
19 3
7
19 4
7
19 5
7
19 6
7
19 7
7
19 8
7
19 9
8
19 0
8
19 1
8
19 2
8
19 3
8
19 4
8
19 5
8
19 6
8
19 7
8
19 8
8
19 9
9
19 0
9
19 1
9
19 2
9
19 3
1994
9
19 5
9
19 6
1997
9
19 8
9
20 9
00
AF x 1000
2500
Year
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)
400
kwh/af
IEUA Website, 2005
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, 1536-1997
5-Year Running Mean
Assessing the 1999-2004 drought in a multi-century context
Source: Woodhouse
8 Periods may be worse than 2000-2004
Source: Woodhouse
Woodhouse, Meko, Gray New Reconstruction of Lees
Ferry Streamflow, 20-year moving average, 1536-1997
Source: Woodhouse
Pluvial (Wet) periods
Dry periods
Highest 20-yr avg. Highest 25-yr avg.
Lowest 20-yr avg. Lowest 25-yr avg
1602-1621 (1)
1905-1929 (1)
1573-1592 (1)
1622-1646 (1)
1601-1620 (2)
1906-1930 (2)
1622-1641 (3)
1623-1647 (2)
1905-1924 (6)
1594-1618 (3)
1870-1889 (4)
1878-1902 (3)
1953-1972 (35)
1953-1977 (28)
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?”