WSP06317

• File Number: 8056
• Description: Drought Preparedness
• State: CO
• Basin: Statewide
• Date: 6/1/1996
• Author: Drought Study Team
• Title: Severe Sustained Drought - Managing the Colorado River System in Times of Water Shortage
• Water Supply Pro - Doc Type: Report/Study

6,

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0030iJ2

COLORADO WATER

June 1996

.,

. Studies of potential environmental impacts of different
hydrologic scenarios;

DROUGHT SCENARIOS

The initial step was to select a representative SSD, and for this
study a hydrologic measure as a basic indicator of drought
was chosen - river nows relative to long~tenn averages.
However. the hydrologic measure was derived from tree ring
srudies of long-tenn climatic behavior.

The hydrologic analysis commenced with an estimated
measure of native flows at Lees Ferry, just below Glen
Canyon Dam in northeastern Arizona. where convention and
iaw divides the Colorado into Upper and Lower Basins,

. Economic projections of water-reiated benefits and costs
of such scenarios;

Explorations of the social impacts of drought in the basin
states; and

. A gaming experiment in changing rules for managing
thesystem as the drought progresses.

The study was conducted
by an interdisciplinary team
from the Universities of
Arizona, California,
Colorado, Nevada and
Wyoming, plus faculty at
Colorado State and Utah
State Universities and the
consulting finn
Hydrosphere, Inc" based in
Boulder, Colorado.

Included on the team were
engineerlhydrologists, tree
ring scientists, attorneys,
environmental scientists,
economists, sociologists
and public administration
specialists, The study
group was overseen by a
consonium of the Water
Research Institutes in the
Colorado River Basin
states, with major funding
provided by the U.s,
Interior Department and the
V,S, Anny Corps of
Engineers,

OBJECTIVES

25

20

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Figu re 2.

The representative 38-
year drought period
adopted for this study
was patterned after (but
not identical to ) the most
severe and long-Ia~ting
dry period identified by
tree ring srudies, the
period for the years 1579
to 1616,

Colorado River Rearranged Severe Drought
and Recovery Period.

....

Analysis period including drought
and recovery 1579 to 1616

~

5

I. Colorado River
Basin Severe Drought

Drought scenarios were
defined in tenns of
aggregate annual flows
(in million acre-feet),
The scenarios included:

.... ~ The period 1579-1600 is
the most severe sustained
Rearranged flows drought that occurred in
tree ring reconstruction of
Lees Ferry streamflow, It
1580 1590 1600 1610 1620 is characterized by a 22-
year mean streamflow of
Year 11.1 maf with mean
streamflow over the first
17 years of only [0.5
maf. compared [0 mean
recorded native streamflow of 15.2 mat). This drought is
estimated to have a return period between 400 to 700 years.

Taking the present-day configuration of the storage and
diversion structures and [he economic conditions in the
Basin as the base-point, Phase II objectives were:

.

2. Colorado Drought in Historic Record

The period 1943 to 1964 is the most severe drought that
occurred in the observed Lees Ferry streamflow record dating
to 1906, II is characterized by a 22-year mean flow of 13.4
maf(eompared to the observed mean 'of 15.2 mat), The return
period is estimated to be between 50 and 100 years, regardless
of uncenainty in tree ring reconstructions of streamflow.

To assess the hydrologic impacts of a Severe Sustained
Drought (SSD);

.

To forecas[ [he economic, social and environmental
impacts on the southwestern U.S,; and

To assess po[ential altema[ive institutional arrangemen[s
for coping with an SSD,