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
1 2 Colorado River
Stakeholders:
Seven western states (CO, WY, UT, NM, AZ, NV, CA) Federal Government Dozens of Indian tribes Mexico
Use of Colorado River water:
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)
Colorado River
Controversial issues:
Allocations for individual states Water transfers from agriculture to urban users Endangered species and other environmental issues Recreation American Indian water rights
Extenuating circumstances:
Water allocations to states in the 1920’s based on unrealistically high flows
Prolonged recent drought
3 Colorado River Flow at 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
4 Water Development
• 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
• 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
• 1920 – 7-State compact proposed
• 1923 – 6-State compact reached (AZ did not agree)
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
5 6-State compact sets the stage for major water projects
• 1931 - Boulder Canyon (Hoover) Dam
• 1940 - All-American Canal
• 1941 - Colorado River Aqueduct to San Diego and LA area
• 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
Current Issues – Upper Colorado Basin
The upper basin states have yet to fully use their share of Colorado River water (6 million ac-ft) in most years. However, demand is rising.
• 52% Colorado • 23% Utah • 11% New Mexico • 14% Wyoming
Current controversial issues
Growth and increasing water demand Prolonged drought Demands for endangered fish species
6 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.
7 8 Salton Sea
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).
9 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.
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
• Evaporation ponds to concentrate salts in parts of lake (~$1.6 b)
• Use water for cities and agriculture and let lake dry up
10 Salton Sea
Salty wasteland?
Environmental and recreational treasure?
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.
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.
11 Water quality dramatically worsened in the 1960’s
• 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.
Î 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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