Southwest Hydrology: The Resource of Semi-Arid Hydrology Volume 4 Number 2

• Description: Southwest Hydrology: The Resource of Semi-Arid Hydrology Volume 4 Number 2
• State: CO
• Date: 3/1/2005
• Title: Southwest Hydrology: The Resource of Semi-Arid Hydrology Volume 4 Number 2
• Water Supply Pro - Doc Type: Publication

Ben Harding — Hydrosphere Inc.
n the early 1990s, a group of scientists, engineers, and lawyers
who were concerned that the modern record of precipitation
in the Southwest is not typical for the area investigated the
potential occurrence, consequences, and anticipated responses to a
"severe and sustained drought" in the Colorado River Basin. They
characterized and modeled the hydrologic, social, environmental,
and economic impacts of a 38 -year period encompassing a
drought similar to the most severe and long- lasting dry period
identified in the tree ring record. The study team formulated and
assessed a series of potential policy responses using computer
simulation and real -time gaming experiments. The basic policy
evaluated was the existing "Law of the River" and the assessments
extended to alternative institutional options, such as changes in
river management. Results of this study, the Severe and Sustained
Drought (SSD) Project, were published in a special edition of
Water Resources Bulletin (Vol.31 No.5, 1995). At the time,
the study raised only mild and fleeting interest among water
resources professionals.
In 2002, the contents of Lake Powell on the Colorado River
dropped by almost 5 million acre -feet (maf), the largest single -
year decline since Glen Canyon Dam was completed in 1963.
Further declines followed in 2003 and 2004. By the end of
September 2004, water levels had declined for five straight years
and Lake Powell was less than 40 percent full, at 9.2 maf. This
situation provoked renewed interest in the SSD Project: what
had been considered an abstract, academic study was suddenly
more relevant. How does the unfolding drought in the Colorado
River Basin compare with the scenario used as the basis for the
SSD study?
We find ourselves in the current
drought with almost 20 maf less water
in the principal reservoirs than at a
corresponding point in the SSD analysis...
In some respects this question cannot yet be answered because the
drought has not reached its denouement. We know neither how
long it will last nor how intense it will be. But indications are that
the onset of this drought is at least as intense as the SSD study
drought. More significantly, we entered this drought with lower
reservoir contents and higher levels of water use than we had
assumed in 1991 would be the case.
24 • March /April 2005 • Southwest Hydrology
1. Lees Ferry Natural Flows
SSD Drought vs. 1995 -2004 Conditions
b 25.00
E 20.00
915.00-,-
m 1 0.00
5.00
a 0.00
3 5 7 9 1113151719212325272931333537
Drought Year
2. Lake Powell Volume
SSD Drought vs. 1995 -2004 Conditions
25
y 20
-,5
E10
> 5
0
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37
Drought Year
3. Lake Mead Withdrawals and Evaporation
SSD Drought vs. 1995 -2004 Conditions
14
c u 12
10
gr
- 3
o� 5
ro J 4
w 2
0
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37
Drought Year
4. Lake Mead Volume
SSD Drought vs. 1995 -2004 Conditions
30
b 25
E 20
E 15
u 10
>
Nf
5
0
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37
Drought Year
3. Lake Mead Withdrawals and Evaporation
SSD Drought vs. 1995 -2004 Conditions
u
w 12
£ 10
C 3
o
e„ 6
ro o 4
w 2
0
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37
Drought Year
SSD 1995 -2004