colorado river basin3 overview of the colorado river system •16.5 million acre-feet (maf)...
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Colorado River Basin: System Status Update and Outlook
for 2018 and 2019
Daniel BunkRiver Operations Manager
Boulder Canyon Operations Office, Lower Colorado Region
Colorado River Citizens Forum in Yuma, Arizona
January 24, 2018
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Topics
• Overview of the
Colorado River Basin
• Colorado River Drought
• Projected Conditions
• Drought Response
Activities
• Summary
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Overview of the Colorado River System
• 16.5 million acre-feet (maf) allocated
annually
- 7.5 maf each to Upper and Lower
Basins and 1.5 maf to Mexico
- 13 to 14.5 maf of basin-wide
consumptive use annually
• 16 maf average annual “natural flow”
(based on historical record)
- 14.8 maf in the Upper Basin and 1.3 maf
in the Lower Basin
• Inflows are highly variable year to year
• 60 maf of storage (nearly 4-times the
annual inflow)
• The System is operated on a type
hydrologic budget
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Natural Flow
Colorado River at Lees Ferry Gaging Station, ArizonaWater Year 1906 to 2018
0
5
10
15
20
25
30
0
5
10
15
20
25
30
An
nu
al
Flo
w (
MA
F)
Water Year
Colorado River at Lees Ferry, AZ - Natural Flow
Average 10-yr Moving Average
Provisional data, subject to change Estimated values for 2016-2018
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Water Budget at Lake Mead
Given current water demands in the Lower Basin
and Mexico, and a minimum objective release
from Lake Powell (8.23 maf), Lake Mead storage
declines by about 1.2 maf annually (equivalent to
about 12 feet in elevation).
Inflow 9.0 maf(Powell release + side inflows above Mead)
Outflow -9.6 maf
(Lower Division State apportionments and
Mexico Treaty allocation, plus balance of
downstream regulation, gains, and losses)
Mead evaporation loss -0.6 maf
Balance -1.2 maf
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1,000
1,025
1,050
1,075
1,100
1,125
1,150
1,175
1,200
1,2251
93
7
194
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1952
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Ele
va
tio
n (
ft)
January 1937 - December 2017
Lake Mead End of Month Elevation
Spillway Crest 1221 ft
December 2017 39% of Capacity
September 199995% of Capacity
In July 2016, Lake Mead was at its lowest elevation of 1,071.61 feet since it was first filled in the 1930s.
During the 1950s drought, Mead reached a low of 1,083.23 feet in April 1956.
Spillway Crest 1221 ft
Prior to 1999, Lake Mead was last at elevation 1,082.52 feet in June 1937.
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Lake Mead near Hoover Dam in 2000 Lake Mead near Hoover Dam in 2016
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Lake Mead – Key Elevations1,2
Not to scale
1,000 ft
1,086 ft* 10.5 maf*40% of Live
Capacity
895 ft
1,229 ft
Dead Pool Storage 2.5 maf
1,145 ft
1,075 ftLevel 1 Shortage Conditions
U.S. Lower Basin Shortage = 333 kaf
Mexico Reduction = 50 kaf1,050 ft
1,025 ft
Level 2 Shortage ConditionsU.S. Lower Basin Shortage = 417 kaf
Mexico Reduction = 70 kaf
Level 3 Shortage ConditionsU.S. Lower Basin Shortage = 500 kaf
Mexico Reduction = 125 kaf
)
Flood Control or Surplus Conditions
Normal or ICS Surplus Conditions
27.6 maf
17.1 maf
9.6 maf
6.0 maf
4.5 maf
0.0 maf
7.7 maf
*As of January 23, 20181 U.S. Lower Basin shortage volumes based on the 2007 Interim
Guidelines (in place 2007-2026).2 Mexico reductions based on Minute 323 (in place 2017-2026).
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118%
64% 65%
24%
57% 55%
118%
80% 81%
112%94%
78%
147%
45% 47%
96% 94% 89%
110%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
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Pe
rce
nt C
ap
ac
ityV
olu
me
in
MA
F
End of Water Year
Unregulated Inflow into Lake PowellPowell-Mead Storage and Percent Capacity
Powell and Mead Storage (MAF) Unregulated Inflow into Powell (MAF) Powell and Mead Percent Capacity
1 Percentages at the top of the light blue bars represent percent of average unregulated inflow into Lake Powell for a given water year. The percent of average is based on the period of record from 1981-2010.
State of the System (Water Years 1999-2017)1
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As of January 22, 2018
Snowpack is 66% of
median
Upper Colorado River Basin Water Year 2018 Snowpack and Forecasted Inflow
Water Year
2018
Forecasted
Inflow into
Lake Powell
6.7 maf (62% of average)
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Most Probable End of CY 2018
Projection: 1,079.5 feet (38% full)
Min/Max Range: 1,076 to 1,083 feet
Most Probable End of CY 2019
Projection: 1,074.7 feet (37% full)
Min/Max Range: 1,062 to 1,108 feet
End of CY 2017 Elevation:
1,082.5 feet (39% full)
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Drought Response Activities
• Through 2017, storage and conservation
programs have resulted in nearly 20 feet of
additional elevation in Lake Mead
- U.S. Intentionally Created Surplus
- Mexican deferred delivery
- Lower Basin Drought MOU voluntary
protection volumes
- Pilot System Conservation Program
- Other system conservation agreements
• Additional Lower Basin drought response
discussions are on-going
- Goal is to reduce the risk of reaching
critically low Lake Mead elevations
through voluntary actions
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Lower Basin Shortage and Surplus Projections1,2
5-Year Outlook
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1 Percentages computed from 110 hydrologic inflow sequences based on
resampling of the observed natural flow record from 1906-2015.2 Percentages shown may not be representative of the full range of future
possibilities that could occur with different modeling assumptions.
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Summary
• The Colorado River Basin
continues to experience an
unprecedented drought
• Even with above average inflow
and a slight improvement in
system conditions in 2017,
there is a chance for Lower
Basin shortage as early as
2019
• Cooperation and collaboration
will be key in finding
sustainable solutions and
addressing current and future
challenges
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For more information:
https://www.usbr.gov/lc/riverops.html