Colorado River
Drainage Basin
250,000 mi2
1,450 miles long
Originates at over
10,000 ft in the
Rocky Mtns in CO
Flows in the
Gulf of California
Colorado River
Colorado River
Stakeholders:
Controversial issues:
Seven western states (CO, WY, UT, NM, AZ, NV, CA)
Federal Government
Dozens of Indian tribes
Mexico
Allocations for individual states
Water transfers from agriculture to urban users
Endangered species and other environmental issues
Recreation
American Indian water rights
Use of Colorado River water:
Extenuating circumstances:
3.5 million acres of farmland
electricity for 3 million people
Water for ~25 million people
(Denver, Salt Lake City, Las Vegas, Phoenix,
San Diego and 100’s of other communities)
Water allocations to states in the 1920’s based on
unrealistically high flows
Prolonged recent drought
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Colorado River Flow at Lee’
Lee’s Ferry
Long term average flow ~15 million ac-ft
Large year-to-year fluctuations (5-25 million ac-ft)
Frequent long drought cycles
Water allocations in the 1920’s based on higher than
average flow
History of the Colorado River Basin
•
600 AD Anasazi Indian develop a canal system for irrigation
and drinking water in Chaco Canyon, NM. Used until
mid-1100’s
•
During the same time, Hohokam Indians built 250 miles of
canals for water from the Salt and Gila Rivers. Used
until the 1400’s
•
Spanish explorers looking for gold in the 1600’s
•
1857/58 steamboat expedition 420 miles upstream
•
1869 John Wesley Powell led three wooden row boats down
the Colorado through Grand Canyon
Water Development
•
1905 - headgates of Imperial Valley Canal flooded diverting
entire river into a natural low spot creating the Salton Sea
•
Flooding and 1910 Mexican revolution provided additional
impetus for construction of the All-American Canal
•
From the beginning upper-basin states were concerned
that California could establish senior appropriative rights
before they could use their water
•
First water use by Imperial Valley, CA farmers via canal through
Mexico
•
Farmers wanted a canal that was entirely on US territory, the
“All-American Canal” but need Congressional support
•
Congressional support required an agreement of Basin states
•
1902 Bureau of Reclamation established which promptly develops
a comprehensive plan for Colorado River development
6-State compact sets the stage for major water projects
•
1931 - Boulder Canyon (Hoover) Dam
•
1940 - All-American Canal
•
1920 – 7-State compact proposed
•
1941 - Colorado River Aqueduct to San Diego and LA area
•
1923 – 6-State compact reached (AZ did not agree)
•
1944 – After repeated appeals and loss in Supreme Court,
Arizona signed on to 6-State compact and started to pursue
its own federal water projects (Central Arizona Project
pumping water up to Phoenix and Tucson)
•
1963 – Glenn Canyon Dam
•
1968 – Grand Canyon Dam eliminated
Upper basin to send 75 million ac-ft downstream over
each 10-year period (7.5 million ac-ft per year on average)
to California and Nevada
California’s allocation is 4.4 million ac-ft plus not more
than half of any surplus water
Arizona was concerned because the compact did not
allocate a specific amount of water to each state
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Current Issues – Upper Colorado Basin
The upper basin states are now fully using their share
of Colorado River water (6 million ac-ft) in most years.
Water demand is still rising.
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•
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•
52% Colorado
23% Utah
11% New Mexico
14% Wyoming
Current controversial issues
Growth and increasing water demand
Prolonged drought
Demands for endangered fish species
December 2007 Water Sharing Accord
Current Issues – Lower Colorado Basin
Water use is constantly increasing. In 1989, for the first time, the
lower basin used up its entire 7.5 m ac-ft allotment.
California has been using more than its 4.4 m ac-ft
Apportionment every year since 1985 but will need to reduce
water use because growth in other states will use up any
surplus.
Largest user of water is agriculture, Imperial Irrigation District
alone uses 2.8 m ac-ft per year to irrigate a 25x40 mile area in the
southeast of California.
Under pressure from the Federal Government, in 2003 California
agreed to reduce water use by conservation measures in the
Imperial Valley and transfer 200,000 ac-ft from IID to San Diego.
Storage in
Lake Powell
State and Federal accord to be in effect until 2026.
If the system is not able to deliver the 7.5 m ac-ft allotment to
the lower basin states, Department of Interior declares a
shortage and cuts water deliveries to the lower basin states.
Las Vegas area (which gets 90% of its water from the Colorado
will get a greater share of Lake Mead water in exchange for
financing a reservoir in California that can capture water
destined for Mexico but beyond Mexico’s entitlement.
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Salton Sea
Tree Ring Studies of the Colorado River Basin
over the last 800 years
•
9 major droughts lasting 15 – 20 years
•
4 major droughts lasting more than 20 years
•
Current drought is one of the most severe in the last 800 years
•
New studies indicate a 70-year “megadrought” in the mid 1100s
In 1905 the
headgates of the
Imperial Canal
flooded, redirecting
the entire Colorado
River into a natural
low spot, the Salton
Sink.
This accident
created California’s
largest freshwater
lake (375 mi2).
Salton Sea has no natural
outlet and has become
increasingly saltier.
Currently about 4.8% salt.
Salton Sea is now fed by
1.3 m ac-ft per year of
irrigation return flow.
A productive fishery for
salt water fish is
threatened by increasing
salinity.
Salton Sea has become a
major stop for migrating
birds (408 species).
“Wasteful” water use by Imperial Valley Farmers maintains the
Salton Sea.
$ 6 billion habitat plan developed by the US Geological Survey
and supported by California Department of Conservation
If water is used more efficiently so some if it can be transferred to
San Diego, salinization of the Salton Sea would accelerate and the
sea would eventually dry up.
Options for dealing with the Salton Sea:
•
Do not irrigate land and put fresh water in the lake
•
Continue letting irrigation return flow run into the lake
•
Evaporation ponds to concentrate salts in parts of lake (~$6 Billion)
•
Use water for cities and agriculture and let lake dry up
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Salton Sea
Salty wasteland?
Long Term Issues for Colorado Basin Water Quality
The name sake reddish color of the Colorado River is due to large
amounts of sediment and dissolved minerals (salts).
Colorado River carries 9 m tons of salt annually and flows through
a region where soils and sediments are salty to start with.
Environmental and
recreational treasure?
At the intake of the Imperial Canal, water contains 2000 lb of salt
per ac-ft.
Because the Colorado River is not flowing into the ocean anymore,
all this salt remains in the basin and accumulates on irrigated
lands.
Water quality decreases downstream with Mexico getting the worst
water.
Water quality dramatically worsened in the 1960’s
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Î
Closing of Glenn Canyon Dam
A Bureau of Reclamation project in the Wellton Mohawk area
with poor drainage and salty soils adds irrigation return
flow containing 6,300 ppm TDS to the Colorado.
Colorado River salinity in Mexico increased from 800 ppm
to 1500 ppm TDS
1973 Treaty to improve Mexico water quality
$250 m Yuma Desalination Plant for treating 80,000 ac-ft of water
from 60,000 ac of salty farmland east of Yuma.
Desalination facility operated briefly in 1992 but flooding of the
Gila River washed out delivery facility. Has not operated since.
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