Colorado River Basin
Supply and Demand
Study
What’s Normal and
What’s New?
Disclaimer
The views presented are my interpretation of the
results and important issues from the Colorado
River Basin Supply and Demand Study. These
views do not represent the official views of the
Colorado Water Conservation Board, the
Colorado Attorney General’s Office, the Colorado
Division of Water Resources, the Colorado River
District, the Southwest Water Conservation
District, the Front Range Water Council, the
[insert name here]…….
Colorado River Basin Study Purpose
• Define future imbalances in the water supply
and demand for Colorado River water
• Analyze adaptation and mitigation strategies to
resolve those imbalances
• Study report is not a decisional document but
is considered a call to action for next steps
Colorado River Demand in Colorado *
4,000
Apportionment
* Includes ~250 KAF CRSP Reservoir Evaporation
3,500
USBR CU & Loss Estimate
(2006-2010 Average)
3,000
KAF
2,500
2,000
1,500
1,000
500
0
2015
2035
2060
Current Projected (A)
Slow Growth (B)
Rapid Growth (C1)
Rapid Growth (C2)
Enhanced Environment (D1)
Enhanced Environment (D2)
Lower Basin Demand *
Upper Basin Demand *
12.0
12.0
MAF
8.0
10.0
Apportionment
8.0
MAF
10.0
6.0
6.0
4.0
4.0
2.0
2.0
0.0
0.0
2015
2035
2060
2015
2035
2060
Current Projected (A)
Slow Growth (B)
Current Projected (A)
Slow Growth (B)
Rapid Growth (C1)
Rapid Growth (C2)
Rapid Growth (C1)
Rapid Growth (C2)
Enhanced Environment (D1)
Enhanced Environment (D2)
Enhanced Environment (D1)
Enhanced Environment (D2)
* Upper Basin Includes 0.5 MAF of CRSP Evaporation
Lower Basin Includes 1.2 MAF of Evaporation
“Normal” for Colorado/ Upper Basin
• Colorado and Upper Division Projected
demands do not reach Full Apportionment by
2060
• Colorado and Upper Division Projected
demands are higher than actual depletions
• Lower Division demands exceed Apportionment
currently
Annual Observed Natural Flow
Colorado River at Lees Ferry
Annual Flow
30,000
10-Year Running Average
25,000
Kaf
20,000
15,000
10,000
5,000
0
1906
1916
1926
1936
1946
1956
1966
1976
1986
Ranges from 5.5 MAF to 25 MAF
Mean Annual Flow (1906 to 2008) = 15 MAF
Mean Annual Flow (1991 to 2010) = 13.7 MAF
Mean Annual Flow (1951 to 1970) = 13.2 MAF
1996
2006
Annual Climate Projected Natural Flow
Colorado River at Lees Ferry
Range of Lees Ferry Natural Flow Sequences used in the Downscaled
GCM Projected Scenario
50,000
45,000
40,000
35,000
KAF
30,000
25,000
20,000
15,000
10,000
5,000
0
GCMs Annual Flows Range from 4.2 MAF to 44 MAF
Average Mean Annual Flow for all 112 GCMs = 13.7 MAF
25% of GCMs predict Mean Annual Flow > 15.0 MAF
25% of GCMs predict Mean Annual Flow < 12.5 MAF
“Normal” for Colorado/Upper Basin
• Planning for hydrologic variability and
prolonged drought is normal
• Risk of Lee Ferry Deficit was considered during
the Compact negotiations
• Historical Climate Variability is why the CRSP
Reservoirs were built
“Normal” for Colorado/ Upper Basin
• Shortages in the Upper Basin are primarily due
to limited supply, and are nothing new
• Colorado water users understand risk
• Tributary agricultural users are supply-limited in
the late irrigation season nearly every year
30000
0.60
25000
0.50
20000
0.40
15000
0.30
10000
0.20
5000
0.10
0
0.00
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Ave Monthly Flow
Ave Monthly CIR
Inches
AF
Tomichi Creek at Gunnison
New Normal
• Upper Basin is experienced at planning/
adapting to variable climate and risk
• Lower Basin may not be as “seasoned”
• About ½ of the GCMs result in at least 1 year
of Lee Ferry Deficit between 2040 and 2060
• Climate change vs prolonged drought and
climate variability creates more urgency
New Normal
• Global climate modeling is a new and rapidly
changing science
CMIP 3
CMIP 5
Time Horizon
1950-2099
1950-2099
Emission scenarios
3 (SRES
A2,A1B,B1)
4 (RCP 2.6, 4.5, 6.0,
8.5)
Climate Modeling Groups
14
23
Global Climate Models (GCM)
16
37
Ensemble members
112
234
2°
1°
1/8°
1/8°
Tavg (°C),
P(mm/day)
Tmin(°C), Tavg (°C),
Tmax(°C), P(mm/day)
GCM Regrid Resolution
BCSD Resolution
Monthly Output Variables
New Normal
New Normal
Key Metrics for Colorado
• Lee Ferry Deficit
– Indicates Risk associated with development
of Compact Entitlement
• Upper Basin Shortages
– Indicates Supply for consumptive uses
• Flows at Critical Locations
– Indicates Supply for non-consumptive needs
Options to Mitigate Imbalances
• Options and Strategies investigated
– Increase Supply
– Reduce Demand
– Modify Operations
Indicator Metrics and Signposts
Indicator Metric/
Vulnerability
Lead Time
(years)
Conditions
Lake
Powell
Lake
Mead
Natural 5-year
Mean Flow at
Lees Ferry
Upper Basin
Shortage
Lee Ferry Deficit
5
3490’
NA
12.39 maf
NA
Lower Basin Shortage
(>1 maf over 2 years)
3
NA
1060’
13.51 maf
NA
Lower Basin Shortage
(>1.5 maf over 5 years)
3
NA
1075’
13.51 maf
NA
Mead Pool Elevation
(< 1,000 feet msl)
3
NA
1040’
13.35 maf
NA
0
NA
NA
NA
25%
Upper Basin Shortage
(>25%)
A good Signpost anticipates a vulnerable conditions, but does not trigger
action unnecessarily. Anticipating a potential Lee Ferry Deficit is the key to
responsible future development.
Normal Options
• Large Scale Import Options and Strategies
provide largest benefit
• Desalination from the Pacific Ocean and
imports from other rivers would require long
lead-times to permit
• Conservation and Reuse
• Upper Basin imbalances are not significant;
“Normal” Options and Strategies primarily
benefit the Lower Basin
New Normal Options
• Upper Basin Water Banking Option was
proposed by Conservation Groups primarily
for environmental/recreational flows
• Water Banking could mitigate a potential Lee
Ferry Deficit
• Water Banking is being further considered in
Basin Study Next Steps, by Colorado, and by
the Upper Basin States
Next Steps for Colorado
• Adopt Signpost Approach
• In lieu of spending effort determining
probability of a Lee Ferry Deficit
– Refine the signposts
– Build the technical, legal, and policy requirements
to implement Options and Strategies when
needed
• Support the Lower Basin to find solutions to
their over-apportionment issues
Next Steps for Colorado
• Provide Support for Data Development
– Continue to support Climate Science Research –
not to identify probabilities, but to understand the
future range of possibilities
– Support Conservation Studies to look realistically
at how much demand reduction is possible
– Help Study Team understand legal and policy
implications associated with Conservation, Reuse,
and Water Banking
Colorado’s Challenges
• Drama makes the news
– “Study shows a 3.2 MAF imbalance in the
Colorado River”. Once published, this became the
tag-line.
– No recognition in the Study that imbalances
assume Lower Basin can develop their projected
demands well beyond apportionments.
– No recognition in the Study that Upper Basin has
always experienced shortages
Colorado’s Challenges
• Results can be “picked” to make any point
• “Climate-change projections show 10 to 30
percent less water in the river by 2050.”
(Denver Post, American Rivers)
– Only if you select the driest of the 112 GCMs
– All 112 projections range from 20 percent more to
30 percent less water
– Context is important when reading articles/white
papers published by advocacy groups
“Normal” for Colorado/ Upper Basin
• Study does NOT indicate an immediate crisis
for Colorado, however does highlight the
continued importance of continuing to
considering the Risk of a Lee Ferry Deficit
associated with both current use and future
development