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Climate Change and Water in the West: The Colorado River Basin

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First in the University of Colorado Boulder webinar series addressing climate change and its effect on the environment. Guest speakers are Doug Kenney, Ph.D., Director of the Western Water Policy Program at University of Colorado Law School and Jeff Lukas, Senior Research Associate, Western Water Assessment, CIRES, University of Colorado.
Watch the video replay of this webinar at http://www.learnmoreaboutclimate.org.

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Climate Change and Water in the West: The Colorado River Basin

  1. 1. Challenges for the Colorado River Basin October 16, 2013 Doug Kenney, Ph.D. Director, Western Water Policy Program University of Colorado Law School Douglas.kenney@colorado.edu Jeff Lukas Senior Research Associate, Western Water Assessment CIRES, University of Colorado Lukas@colorado.edu 1 www.learnmoreaboutclimate.org www.cires.colorado.ed u Organized by: Anne Gold, Ph.D. CIRES and Deb Morrison, CU Boulder School of Education Produced by: Kit Seeborg for Learn More About Climate
  2. 2. Climate Change & Water in the West Webinar Facilitators 2 Deb Morrison Ph.D. Candidate CU Boulder, School of Education Margi Dashevsky CU Boulder Anne Gold, Ph.D. CIRES, Education & Outreach Kit Seeborg LearnMoreAboutClimate.org
  3. 3. Water in the West Webinar Series  Overall Structure ◦ Two webinars ◦ Background reading material on the website  Requirements For Credit  More Webinar Series to come ◦ Extreme Weather in Spring 2014 3
  4. 4. Major rivers of the U.S. 4
  5. 5.  1,450 miles long  Basin covers 246, 000 sq. mi.  Headwaters in high mountains of CO, WY, UT, NM Colorado River 5
  6. 6. 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 6
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  8. 8. 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
  9. 9. Snowmelt-dominated hydrology: ~80% of annual flow comes April 15- July15 Gaged daily flow, Colorado River at Lees Ferry, 1950- 1955 9
  10. 10. Colorado River Compact of 1922 (and the Law of the River) Total Allocation of 16.5 MAF  7.5 MAF to the Lower Basin ◦ 4.4 MAF to California ◦ 2.8 MAF to Arizona ◦ 0.3 MAF to Nevada ◦ Doesn’t include LB tributaries  7.5 MAF to the Upper Basin ◦ 51.75% to Colorado ◦ 23% to Utah  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 10
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  12. 12. “A river no more” 12
  13. 13. Data: Reclamation (1906-2010); 2011-13 values estimated from preliminary Reclamation data or projections 0 5 10 15 20 25 30 1900 1910 1920 WaterYearFlow,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 13
  14. 14. 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 WaterYearFlow,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 14
  15. 15. Tree rings tell us the early 1900s was one of the wettest periods of the last 1200 years 10 11 12 13 14 15 16 17 18 750 1000 1250 1500 1750 2000 Water Year AnnualFlow,MAF Tree-ring reconstruction of Colorado River at Lees Ferry streamflow from 762-2005, with 20-year running mean Gage d period Reference: Meko et al. 2007, Medieval Drought in the Colorado River Basin, Geophysical Research Letters Data: TreeFlow: http://treeflow.info/upco/coloradoleesmeko.html 15
  16. 16. 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 16
  17. 17. Photo provided by Jennifer Pitt No flow to the Colorado River delta in most years since Glen Canyon Dam built (1963) 17
  18. 18. The Colorado River’s endangered native fish  Evolved with warm, muddy water conditions  Need off-channel “backwater” habitat for raising young 18
  19. 19. Glen Canyon Dam and Lake Powell 19
  20. 20. Sediment is now trapped behind dams, so downstream water is clear 1963: Glen Canyon Dam built Sediment in Grand Canyon decreases >95% 20
  21. 21. Dams release water from lower levels of reservoir: cold water, less seasonal change 1973 Lake Powell nearly full Water Temperature, Colorado R. at Lees Ferry, 1960-2000 21
  22. 22. 1963: Glen Canyon Dam built Dams cut off the annual peak flows needed to maintain backwater habitat 22
  23. 23. 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 WaterYearFlow,MAF 14.9 million acre-feet long-term average 12.3 million acre-feet average, 2000-2013 23
  24. 24. Causes of low flows since 2000  Main 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 24
  25. 25. 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 AnnualRunoff,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 25
  26. 26. Demands have caught up with supply 0 5 10 15 20 25 1923 1927 1931 1935 1939 1943 1947 1951 1955 1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003 2007 Volume(MAF) Year Total Supply (10-yr running average at Imperial Dam) Total Demand (10-yr running average) 26
  27. 27. Emergence of the “bathtub rings” 27
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  29. 29. 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 29
  30. 30. Basin Study: 4 water supply scenarios, using gaged flows, tree-ring flows, and projected flows 1) Gaged Flows 2) Tree-ring Flows 3) Tree-ring Flows blended with Gaged 4) Projected Flows Less water supply 30
  31. 31. A wealth of possible solutions 31
  32. 32. 0 5 10 15 20 25 30 1950 2000 2050 2100 AnnualRunoff,MAF Uncertainty in future water supply: differences among GCM runs 32
  33. 33. 0 5 10 15 20 25 30 1950 2000 2050 2100 AnnualRunoff,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 33
  34. 34. 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 34
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  37. 37. Water withdrawals for electricity production Kenny et al. 2009 37
  38. 38. Planning for an uncertain future 38
  39. 39. Understanding choices and trade-offs 39
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  41. 41. Change is:  Ever-present is human and natural systems  A challenge for planning and management  An opportunity to do things differently in the future 0 5 10 15 20 25 30 1950 2000 2050 2100 AnnualRunoff,MAF 41
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  45. 45. Watch this webinar’s video replay: http://www.learnmoreaboutclimate.org 45

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