Demographic, legal, and environmental changes can and have disrupted existing relationships and current perspectives about the interactions among society, climate, and water. Nowhere is this more apparent than in the many transbound-ary situations that dominate Colorado River management. The Colorado River has been the subject of extensive negotiations and litigation. The federal government accounts for
56% of the land within the basin; Indian reservations, 16.5%; states, 8.5%; and private ownership, 19% (Weatherford and Brown, 1986). As a result, a complex set of federal laws, compacts, court decisions, treaties, state laws, and other agreements collectively known as the "Law of the River" has been developed (Table 1). These play out in terms of interstate agreements (e.g., the Colorado River Compact) and transnational (U.S.-Mexico) settings. A study by an alliance of seven western water resources institutes (Powell Consortium, 1995) offers the following counterintuitive result: Although the Lower Colorado River Basin within the United States is indeed drier than the Upper Basin, it is the Upper Basin that is vulnerable to severe, long-term climatological drought because of the 1922 agreement to provide a fixed amount of water to the Lower Basin. However, the Lower Basin is subject to water supply limitations brought on by growth and inflexible allocation arrangements. This unprecedented growth has occurred during a wetter-than-average 25-year period (1975-99), which may have resulted in some degree of complacency about water availability.
The chronology in Table 1 reflects the changing values of water rights in the new West based on tourism and recreational economies. Management has evolved from two classic approaches to integrated river basin development: (1) large-scale investments in water projects integrating economic and engineering objectives, and (2) negotiation of inter-state and international agreements for the management of shared resources.
Recently, emphases have shifted to integration of irrigation with other agricultural land uses, wastewater reuse, and conjunctive management of ground and surface water systems. Most important are the trends toward public involvement and participation in decision-making processes and the incorporation of institutional and behavioral considerations in the planning and implementation processes.
Frederick et al. (1996) concluded that in the upper Colorado region the value of water for recreation, fish, and wildlife was US$51 per acre-foot, compared to US$21 for hydropower and US$5 for irrigation. Even given the limited
Table 1 The Colorado River: Relevant Events and Agreements, 1902-2004.
1902 Arthur Powell Davis, USGS engineer (future head of the Bureau of Reclamation), proposes "the gradual comprehensive development of the Colorado by a series of large storage reservoirs."
1905 Flood waters break into Imperial Valley, creating the Salton Sea over 2 years.
1920 Kincaid Act authorizes data gathering for the All-American Canal. Population of Los Angeles reaches 600,000 (600% more than in 1900). Mulholland and Scattergood endorse Davis's plan to use Colorado to meet "all future electricity needs." Denver population reaches 260,000 (100% increase since 1900).
1922* Colorado River Compact. Upper and Lower Basins demarcated at Lees Ferry. All basin states except
Arizona ratify agreement. Indian rights considered "negligible."
1923 Dry year. Los Angeles looks to Colorado for water as well as electricity.
1927 Metropolitan Water District of Southern California approved by state legislature.
1928* Boulder Canyon Act (BCA) approved in Congress. Authorizes construction of Hoover Dam. 1922 compact ratified. Lower Basin allotments apportioned.
1930 Arizona v. California. Arizona requests that the BCA be declared unconstitutional.
1931* California Seven Party Agreement on municipal vs. agricultural use
1935 Hoover Dam completed. California purchases all power produced.
1944* Colorado River Compact ratified by Arizona.
1945 Mexican Treaty approved in Congress, with support from Upper Basin, Arizona, and Texas. Mexico receives
1.5 maf despite objections from California.
1948* Upper Basin Compact: Allots Colorado 51.75%, Utah 23%, Wyoming 14%, New Mexico 11.25% (and 50,000
af to Arizona above Lees Ferry).
1956* Colorado River Storage Project Act. Arizona v. California.
1963 Glen Canyon Dam completed. Lake Powell begins filling. Indian uses charged against the state in which a reservation was located.
1964 Arizona v. California Supreme Court decision. Settles 25-year dispute. Allows Arizona's decision to build the Central Arizona Project (CAP) to fully use its allotment.
1968* Colorado River Basin Project Act. Construction of major water developments in both Upper and Lower
Basins. CAP designated junior right. 1970* Criteria for Coordinated Long-Range Operation of Colorado River System. Glen Canyon Dam releases to maintain balance between Lake Powell and Lake Mead. 1973* Minute No. 242 of the U.S.-Mexico International Boundary Commission.
1974* Colorado River Basin Salinity Control Act. Authorized desalination and salinity control projects (including
Yuma Desal Plant).
1987 Increased generator capacity and resulting changes in operations require environmental impact statement
(EIS) for Glen Canyon Dam. 1994 Draft EIS issued. U.S. Fish & Wildlife Service BiOp on Glen Canyon operations.
1996 Controlled flood released from Glen Canyon Dam.
2001 Colorado River Interim Surplus Guidelines. Surplus in Lower Basin to be divided between California and
Arizona. Quantification Settlement Agreement. 2004 Worst drought period in 100 years continues (since 1999).
Note: Asterisked (*) years denote passage of principal documents forming the "Law of the River."
reliability of the precision of these numbers, they reflect changing values of water rights in the new West based on tourism and recreation. Booker and Young (1994) concluded that efficient administration would require a large reallocation from the Upper Basin to the Lower Basin to reflect the low marginal values of irrigation water in the Upper Basin and the high instream values generated between the two basins. Efficiency is obviously not the only criterion for management of a multifaceted and socially constrained resource such as water. In the case of the Colorado it has become virtually impossible to answer the question "Who manages this basin?" (even with the Secretary of the Interior designated as "water master" for the Lower Basin) without listing dozens of government agencies, legal and diplomatic instruments and precedents, private-sector interests, and community-based interests (Varady et al., 2001). Climate-sensitive decisions in the Colorado River basin thus involve and cross the many temporal and spatial scales through which water of varying quantity and quality flows (Pulwarty and Melis, 2001).
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