The Colorado River

The Colorado River Compact (1922)

• The Colorado River Compact divides the Colorado River into Upper and Lower Basins with the division being at Lees Ferry on the Colorado River one mile below the Paria River in Arizona.

– The Lower Basin states are Arizona, California, and Nevada, with small portions of New Mexico and Utah that are tributary to the Colorado River below Lees Ferry.

– The Upper Basin states are Colorado, New Mexico, Utah, and Wyoming, with a small portion of Arizona tributary to the Colorado River above Lees Ferry.

• The Compact apportions the right to exclusive beneficial consumptive use of 7.5 million acre-feet of water from the "Colorado River System" in perpetuity to the Upper Basin and the Lower Basin

• It provides water for Mexico pursuant to treaty. Water must first come from any surplus over the waters allocated to the states

• Upper Basin states will not withhold water and the states of the Lower Basin shall not require delivery of water which cannot reasonably be applied to domestic and agricultural uses

Boulder Canyon Project Act (1928)

• This Act authorized the construction of Hoover Dam and the All-American Canal to the Imperial Valley in California. It also, in effect, apportioned the Lower Basin states' allocation under the Colorado River Compact. Below are the volumes of water given to the Lower Basin states: – California--4.4 million acre-feet – Arizona--2.8 million acre-feet – Nevada--0.3 million acre-feet

• Arizona was also given exclusive beneficial use of the Gila River outside of the mainstem allocation of 2.8 million acre-feet.

Hoover Dam (Boulder Canyon Project)

Mexican Treaty (1944) • In 1944, the United States and Mexico signed a

treaty concerning the waters of certain international rivers, including the Colorado River.

• The treaty guaranteed a scheduled annual delivery of 1.5 million acre-feet to Mexico (except in the event of an extraordinary drought or serious accident) and up to 1.7 million acre-feet per year in years of surplus on the Colorado River

Upper Colorado River Compact (1948)

• In 1948, the Upper Basin states entered into a compact which apportioned among themselves the waters of the Colorado River available to the Upper Basin by the 1922 Colorado River Compact.

• The 1948 Compact apportioned to Arizona 50,000 acre-feet per year while the other Upper Basin states received a percentage of the remaining apportionment as follows:

– Colorado . . . . . . . . . . . . . 51.75% Utah . . . . . . .. . . . . . . . . . 23.00% Wyoming. . . . . . . . . . . . . 14.00% New Mexico . . . . . . . . . . 11.25%

•

• Under this formula, if 7.5 million acre-feet were available to the Upper Basin annually, Colorado's apportionment would provide for the consumptive use of 3,855,375 acre-feet of water annually.

• As of 1985, Colorado only beneficially consumed an average of 2.3 million acre-feet of Colorado River water annually.

• The Compact also provides that any of the Upper Basin states may exceed the basic apportionment provided that it does not deprive another state of its apportionment.

Arizona v. California 373 U.S. 546 (1963)

• Arizona brought suit under the original jurisdiction of the U.S. Supreme Court in 1952 to resolve its dispute with California over rights to use the Lower Basin apportionment of the Colorado River Basin Compact.

• Much to California's dismay, the Supreme Court held that by passing the Boulder Canyon Project Act, Congress had, in effect,apportioned the mainstem of the Colorado River with California receiving 4.4 million acre-feet, Arizona 2.8 million acre-feet, and Nevada 0.3 million acre-feet.

• Furthermore, the Court found that the Boulder Canyon Project Act allowed Arizona and Nevada the exclusive use of their tributaries, which did not support the Upper Basin states' position that the Mexican Treaty obligation should be satisfied from flows in the Lower Basin in excess of their apportionment, much of which was intended to come from Lower Basin tributaries.

Colorado River Basin Project Act (1968)

• With the decision from Arizona v. California in its favor, Arizona sought Congressional authorization of the Central Arizona Project (CAP) in 1963.

• The Act was approved in 1968 with many features, including the following: – Authorization of the CAP – Five authorized projects in Colorado (Animas-La Plata,

Dolores, Dallas Creek, West Divide, and San Miguel) – Investigation of methods for augmenting the flow of the

Colorado River – Computation of consumptive uses by the Secretary of the

Interior – Development of operating criteria for the coordinated Storage

Project Act and the Boulder Canyon Project Act (Lake Mead) by the Secretary of the Interior.

The Central Arizona Project

Central Arizona Project • Constructed by the

Bureau of Reclamation between 1973 and 1992, the Central Arizona Project can deliver approximately 1.5 million acre-feet (488 billion gallons) of Colorado River water each year for cities, industries, Indian communities and agricultural areas in central and southern Arizona.

Coordinated Long Range Operating Criteria--Colorado River Reservoir (1970)

• These operating criteria control the coordinated long-range operation of storage reservoirs and projects in the Colorado River Basin constructed under the authority of: – Colorado River Storage Project Act (i.e. Powell,

Flaming Gorge, Aspinall Unit, Navajo, and participating projects),

– Boulder Canyon Project Act (i.e. Lake Mead) – Colorado River Basin Project Act (i.e. Central

Arizona Project).

Coordinated Long Range Operating Criteria--Colorado River Reservoir (1970)

• The operating criteria also provide for the release of water from Lake Mead to meet Mexican Treaty obligations, reasonable consumptive use requirements of mainstem users in the Lower Basin, net river losses, net reservoir losses, and regulatory wastes.

– Until such time as these demands exceed 7.5 million acre-feet in the Lower Basin a normal water supply condition exists in the Lower Basin. Criteria for determining surplus and shortage conditions are also contained in the criteria.

– When Reclamation further considers the yield to the Upper Basin during the critical period of record (drought period) the yield to the Upper Basin may only be 6.0 million acre-feet annually

• It has been demonstrated that the yield of the Colorado River System is less that what the 1922 compact negotiators originally believed.

– At Lee Ferry the yield only averages 15.0 million acre-feet annually. – To the Upper Basin this means that its compact entitlement may be reduced by

one-half the Mexican Treaty obligation or 750,000 acre-feet. While the Upper Basin states do not agree with this interpretation, the operating criteria still contain a minimum annual objective target release for Lake Powell of 8.23 million acre-feet annually

Colorado River Flow over 500 Years

USGS Drought Simulations• The drought simulations

indicated that, under current management practices, a severe sustained drought would heavily impact the Upper-Basin States of the Colorado River (above Compact Point) but would have limited impact on water use in the Lower Basin.

USGS Drought Simulations• Three main conclusions were indicated by the simulations:•

– Even the fiendish progressively deepening, 19-year, worst-case, Severe Sustained Drought formulated by Tarboton (1995) was not enough to completely drain the reservoirs of the Colorado River system. Some users would survive with only a limited period of impacts, but some users in both basin would be impacted eventually.

– The Upper Basin is more vulnerable to impacts from a severe drought than is the Lower Basin, largely because many Upper Basin water rights are effectively or actually junior with respect to Lower Basin rights under the Law of the River.

– Non-consumptive and environmental water uses are more vulnerable to drought under the current Law of the River than are the consumptive uses. The current Law of the River is mostly designed to guarantee rights to diversions from the river, rather than instream uses.

• Coping with Severe Sustained Drought in the Southwest (USGS)

Colorado River Basin Salinity Control Act (1974)

• Mexico had been complaining about the increasing salinity of Colorado River waters reaching its border. As a result, after years of negotiations and interim agreements, the nations signed Minute 242 of the International Boundary and Water Commission.

• This action committed the United States to delivering water to Mexico from the Colorado River containing no more than 115 parts per million of salt than the salt content of the water diverted to the All-American Canal at Imperial Dam (Imperial Valley).

• With this obligation, the Colorado River Basin Salinity Control Act was passed to initially fund four salinity control projects. The Act has subsequently been amended to include a number of other projects.

Yuma Desalting Plant• The salinity of the Colorado River

at its source high in the Rocky Mountains is about 50 parts per million (ppm).

•• Before development of the West,

the salinity at the northern Mexico border was about 400 ppm. During the 1960s, the salinity at the border increased to concentrations as high as 1,200 ppm.

• This increase was caused by the return flows of numerous irrigation projects and cities along the river, where unabsorbed irrigation water percolated through mineral-rich soils and dissolved the minerals.

Yuma Desalting Plant• As the world's largest reverse

osmosis desalting plant, it can produce about 275,000 cubic meters or 275 million liters (72.4 million gallons) of desalted water per day

• It helps the United States meet salinity requirements for Colorado River water delivered to Mexico

• It desalts and salvages the drainage water that otherwise would be too saline to deliver to Mexico, thus saving the U.S. up to 97 million cubic meters (78,000 acre-feet) of Colorado River water per year.

Yuma Desalting Plant• Construction of the Yuma

Desalting Plant was completed in 1993, but the facility operated, for testing, only in 1994.

• Since then, water storage in the Colorado River reservoirs has been adequate to meet all requirements.

• Continued drought in the river basin may require operation of the plant in the near future.

California’s water supply

• The California Department of Water Resources estimates the state’s developed water supply at 78 million acre-feet.*

• Of that, 46 percent is used by the environment, 43 percent is used on farms and 11 percent is used in homes and businesses.

Developed water supply has not grown with California’s population

• Water supplies to California’s farms, homes and businesses are declining.

• Combined state and federal surface water deliveries currently total approximately 4.8 million acre-feet, a 14 percent reduction from 1990.

• California will grow from 29.8 million people in 1990 to approximately 46 million by 2020, a 54 percent increase.

Reallocation has reducedstate and federal water

supply• Between 1990 and 2000,

as a result of new regulations and laws, approximately 1 million acrefeet of water was reallocated from farms, homes and businesses to improve the environment.

• New infrastructure has not replaced this water.

The Los Angeles Aqueduct

• Completed in 1913, the first Los Angeles aqueduct spans an estimated 223 miles in length, tapping into the waters of the Owens River in central California.

• In 1940 the aqueduct was extend 40 miles north to tap more water sources at tributaries to Mono Lake.

• In 1970, having again out grown its water needs, the city began construction of a second aqueduct doubling the amount of water diverted from the Mono Basin and Owens Valley to Los Angeles.

• The two Los Angeles Aqueducts now deliver an average of 430 million gallons a day to the city.

The Los Angeles Aqueduct

Jawbone Siphon• This is the largest of the pressurized

tubes dipping into and out of the canyons along the Los Angeles Aqueduct (8,095 feet, with a 850 foot drop), and is notable also for having burst in freezing weather in 1988.

• A few of these "siphon points" are visible along the course of the original Los Angeles aqueduct which, when it was built in 1913, was the largest single water project in the world, and was especially remarkable for being gravity powered for its entire 226 mile length.

• In order to flow through valleys the aqueduct is contained in steel pipes, using the pressure developed in the down slope to force the water through the up slope. The Los Angeles Aqueduct supplies Los Angeles with about 70% of its drinking water.

Mono Lake After Diversion of Surface WaterFigure 10.31

10-24 Source:Courtesy of Carla W. Montgomery.

The Colorado River Aqueduct• The MWD aqueduct was under

construction for eight years, and was finished in 1941

• The aqueduct carries water 242 miles, from Lake Havasu, on the Colorado River, to Lake Matthews in western Riverside County

• The aqueduct lifts the water 1,617 feet through five pumping plants. There are 92 miles of tunnels, 63 miles of concrete canals, 55 miles of concrete conduits, and 144 siphons totaling 29 miles

• By 1961, to keep pace with increasing water needs, MWD had expanded the Aqueduct to reach its full delivery capacity of 1,212,000 acre-feet of water annually, or more than 1 billion gallons a day.