an upper basin scientific perspective on the colorado river water supply in the 21st century 31st...
TRANSCRIPT
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 [email protected]
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?”