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Law of the River
The Colorado River is managed and operated under numerous compacts, federal laws, court decisions and decrees, contracts, and regulatory guidelines collectively known as the "Law of the River." This collection of documents apportions the water and regulates the use and management of the Colorado River among the seven basin states and Mexico. Based on this body of law, Arizona has the right to use 2.8 million acre-feet annually of the Colorado River water. When fully utilized, the Central Arizona Project will deliver on average 1.5 million acre-feet (a portion of Arizona’s 2.8 million acre-feet) of Colorado River water to Maricopa, Pinal and Pima Counties. Following is a synopsis of the most significant documents that comprise the Law of the River (you can click on the Link document to get the full text of these regulations):
Colorado River Compact (1922)
The Compact divided the Colorado River Basin into the Upper Basin and Lower Basin which are defined as those states or parts of states from which waters naturally drain into the Colorado River above and below Lee Ferry, respectively. Lee Ferry is a point on the mainstream of the River approximately one mile below the mouth of the Paria River in northern Arizona.
The Compact apportioned, in perpetuity to the Upper Basin and to the Lower Basin, the exclusive beneficial consumptive use of 7.5 million acre-feet of water annually. The Lower Basin was given the right to increase its then current beneficial consumptive use by one million acre-feet annually. The Compact further provided that the two basins would share any burden, which might arise because of a water treaty with Mexico, equally. The Upper Basin was required to restrict its use so that the flow of the river at Lee Ferry would not be depleted below an aggregate of 75,000,000 acre-feet for any period of ten consecutive years. The Compact also established a preference for agriculture and domestic uses over water use for power generation. Link to document
Boulder Canyon Project Act (1928)
This Act authorized the construction of Hoover Dam and Power Plant and the All-American Canal. In addition, the Lower Basin States made provision for the sharing of water, and authorization was given to the Secretary of the Interior (Secretary) to execute contracts for water made available by the Boulder Canyon Project, subject to the terms of the Colorado River Compact.
The provisions of the Act stipulated that it would take effect upon the fulfillment of either of two conditions. The first was that all seven states ratify the Colorado River Compact. Because Arizona was not satisfied with the terms of the Compact, it became impossible to meet this condition. In fact, Arizona did not ratify the Colorado River Compact until 1944. The second condition required that six of the States, including California, ratify the Compact, and that California agree to limit its consumptive use of water from the Colorado River to 4.4 million acre-feet. With the exception of Arizona, all of the Colorado River Basin States ratified the Compact, and passage of The California Limitation Act of 1929 completed the conditions required to make the Act effective. President Herbert Hoover declared the Boulder Canyon Project Act and the Colorado River Compact in effect on June 25, 1929.
The Act also authorized the states of Arizona, California, and Nevada to enter into an agreement whereby the 7.5 million acre-feet of water that was apportioned to the Lower Basin by Article 111(a) of the Colorado River Compact would be apportioned as follows: to California, 4.4 million acre-feet per annum; to Arizona, 2.8 million acre-feet per annum; and to Nevada, 0.3 million acre-feet per annum. The three states, however, were unable to agree on such an apportionment. Link to document
Mexican Water Treaty (1944)
The water treaty between the United States and Mexico involving waters of the Colorado River (and the Rio Grande and Tijuana Rivers) became effective November 8, 1945. The Treaty allocated to Mexico 1.5 million acre-feet of Colorado River system waters annually. The allocation was to be increased in years of surplus to 1.7 million acre-feet and reduced proportionately during years of extraordinary drought. The Treaty dealt with quantity and was silent on the quality of water to be delivered.
In 1962, the Mexican Government formally protested to the United States Government regarding the quality of Colorado River water that was being delivered to the Mexicali Valley. Upon the request of the State Department, the governors of the seven Colorado River Basin States reconstituted the Committee of Fourteen (two water experts from each of the seven Basin States appointed by their respective governors) to advise the State Department and the International Boundary and Water Commission about Mexican water salinity issues and potential solutions.
Numerous meetings and negotiations led to the adoption of Minute 242, executed in 1973, which obligates the United States to implement measures that will maintain the salinity of the Colorado River waters delivered to Mexico at nearly the same quality as that diverted at Imperial Dam for use within the United States. Link to document
Upper Colorado River Basin Compact (1948)
This Compact, dated October 11, 1948, divided the water apportioned to the Upper Basin by the Colorado River Compact between the five States having territory in the Upper Basin. Arizona was allocated 50,000 acre-feet per annum with the remainder of the Upper Basin entitlement divided according to the following percentages: Colorado, 51.75; New Mexico, 11.25; Utah, 23.00; and Wyoming, 14.00. Link to document
Arizona v. California (1964), U.S. Supreme Court Decree (Consolidated 2006)
Failure of the three Lower Basin States to reach agreement on how to further apportion the water allocated to the Lower Basin by the Colorado River Compact, ultimately led Arizona to file suit in the Supreme Court in 1952. The Court concluded that Congress, by enacting the Boulder Canyon Project Act, had provided its own method of allocating water among the Lower Basin States and that this method applied to the first 7,500,000 acre-feet per annum of mainstream water, exclusive of tributary waters. California had argued that the first 7,500,000 acre-feet per annum of Lower Basin water, of which it had agreed to use only 4,400,000, included both mainstream and tributary water - not just mainstream water. Arizona, Nevada, and the United States contended that the tributaries should not be included in the water to be divided, but should remain for the exclusive use of each State.
The 1964 decree apportioned the first 7,500,000 acre-feet per annum of Colorado River mainstream water available to the three Lower Basin States as follows: Arizona, 2,800,000; California, 4,400,000; and Nevada, 300,000. Any excess above 7,500,000 acre-feet was apportioned 50 percent to California and 50 percent to Arizona, except that Nevada was given the right to contract for 4 percent of the excess, which would come out of Arizona’s share. The Court left the allocation of shortages to the discretion of the Secretary after providing for satisfaction of present perfected rights in the order of their priority dates. Present perfected rights (PPR) were defined as rights existing and used prior to June 25, 1929, the effective date of the Boulder Canyon Project Act. The allocation of shortages was later determined by Congress in Section 301(b) of the Colorado River Basin Project Act (1968). Link to AZvCA 1964 , Link to Consolidated Decree 2006
Colorado River Basin Project Act (1968)
This Act authorized the CAP and other water development projects in the Upper Basin. The CAP was to provide the necessary conveyance and storage facilities to import a major portion of Arizona’s remaining share of Colorado River water into the south-central part of the State. The Act also directed the Secretary to prepare long-range water resources studies directed toward the augmentation of the Colorado River, to prepare criteria for the coordinated long-range operation of the Colorado River reservoirs, and to undertake programs for water salvage and groundwater recovery along and adjacent to the mainstream of the Colorado River.
Section 301(b) of the Act provides for the allocation of water in times of shortage. This section provides that the Supreme Court decree in Arizona v. California shall be so administered that in any year in which the Secretary determines there is insufficient mainstream water to satisfy 7.5 million acre-feet of consumptive use in Arizona, California, and Nevada, diversions to the CAP will be limited to ensure the availability of water first to satisfy 4.4 million acre-feet of water use in California and water uses in Arizona and Nevada which predate the CAP. This provision does not in any way affect the relative priorities of water users within each state or the priority of pre-1929 water rights. This limitation is inoperative in any year in which the Secretary proclaims that means are available and in operation, which augment the water supply of the Colorado River in sufficient quantities to satisfy the full 7.5 million acre-feet of consumptive use in Arizona, California, and Nevada.
Section 304(a) of the Act contains a prohibition against using CAP water to irrigate lands not having a recent history of irrigation. “Recent history of irrigation” has since been determined by the Secretary to mean irrigation at some time between September 30, 1958, and September 30, 1968, the date on which the Act became law. Indian agricultural development is not limited by this provision.
Subcontracts for CAP water must contain provisions to control expansion of groundwater use for irrigation in each respective subcontract service area. Furthermore, groundwater pumping from within a subcontractor’s service area for any use outside that service area is prohibited except where it is determined that surplus groundwater exists or that drainage is required.
This Act also declared that the satisfaction of the requirements of the Mexican Water Treaty from the Colorado River constituted a national obligation, which shall be the first obligation of any water augmentation project planned pursuant to the Act and authorized by the Congress. This provision of the Act is very important to the States of the Colorado River Basin, and to Arizona in particular, because of the shortage provision described above.
The Act also directed the Secretary of the Interior to propose criteria for the coordinated long-range operation of federal reservoirs in the Colorado River Basin. These criteria were subsequently developed in cooperation with the Colorado River Basin States and were adopted by the Secretary on June 8, 1970. Link to document
Colorado River Basin Salinity Control Act (1974)
The Salinity Control Act of 1974 (Public Law 93-320) provided the means to comply with the United States’ obligations to Mexico under Minute No. 242. A major feature of the Act included a brine discharge canal and a desalination plant for the conveyance and treatment of Wellton Mohawk Irrigation and Drainage District drainage water (Title I of the Act). These facilities enable the United States to deliver water to Mexico having an average salinity of 115 parts per million (ppm) plus or minus 30 ppm over the annual average salinity of the Colorado River at Imperial Dam. The Act also authorized construction of four salinity control units and the expedited planning of twelve other salinity control projects above Imperial Dam as part of the basin wide salinity control plan (Title II of the Act – see Section on Water Quality).
In 1978, the Colorado River Basin Salinity Control Forum reviewed the salinity standards and recommended continued construction of units identified in the 1974 Act, established effluent limitations for industrial and municipal discharges, and reduced salinity of irrigation return flows. The review also called for the inclusion of water quality management plans to comply with section 208 provisions of the Clean Water Act. It also contemplated the use of saline water for industrial purposes and future salinity control.
Primary responsibility for the federal program was given to the Secretary of the Interior, with Reclamation being instructed to investigate and build several cost effective salinity control units. The Secretary of Agriculture was instructed to support the effort within existing authorities. The Act was amended in 1984 by P.L. 98-569 to authorize two additional units for construction by Reclamation and directed the BLM to implement a comprehensive program to minimize salinity in the Colorado River Basin.
In 1996, Public Law 104-127 significantly changed the authorities provided to USDA. Rather than carry out a separate salinity control program, the Secretary of Agriculture was directed to carry out salinity control measures in the Colorado River Basin as part of the Environmental Quality Incentives Program established under the Food Security Act of 1985. Public Law 104-127 also authorized the Secretary of Agriculture to cost share salinity control activities from the basin funds in lieu of repayment. Cost sharing has been implemented for both USDA and Reclamation programs. Under this new authority, each dollar appropriated by the Congress is matched by $0.43 in cost sharing. Link to document
Photo of Yuma Desalting Plant