Free Flow

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Long-term planning investments paying

dividends: the Colorado River Basin Water

Supply and Demand Study

Carly Jerla, Co-Study Manager and Ken Nowak, Bureau of Reclamation; Kay Brothers, Co-Study Manager,

Southern Nevada Water Authority consultant; Armin Munevar, CH2M Hill; Les Lampe, Black & Veatch;

David Groves and Jordan Fischbach, RAND Corporation

lowing more than 2,300 km from source to sea, the

Colorado River drains a basin of about 637,000 square

kilometres, covering roughly a twelfth of the contiguous

United States. The watershed includes parts of seven US states

(Arizona, California, Colorado, Nevada, New Mexico, Utah and

Wyoming) and two states in northern Mexico (Baja California

and Sonora).

About 40 million people depend on drinking water from the

Colorado River and its tributaries. Additionally, the river irrigates

nearly 5.5 million acres (2.2. million hectares) of farmland and fuels

hydropower facilities that generate more than 4,200 megawatts of

power. It is the force that carved the Grand Canyon and is the life-

blood for more than 20 Native American tribes and communities,

seven national wildlife refuges, four national recreation areas, and

eleven national parks.

Because the Colorado supports such diverse resources, manag-

ing the river has become a complex, multi-objective exercise that

involves stakeholders and resource management entities such as the

federal Government, Native American tribes and communities, state

agencies, municipalities and agricultural districts, advocacy groups,

non-governmental organizations and local governments. It is inevi-

table that these interests often are in conflict – managing the river

equitably requires a strong commitment by all parties.

Reservoir management largely falls within the purview of the

Secretary of the US Department of the Interior, and the Bureau

of Reclamation (Reclamation) is the agency designated to act on

the Secretary’s behalf. Reclamation is the largest wholesale water

supplier in the United States, and numerous Reclamation projects

are located in the Colorado River basin, including Glen Canyon

Dam and Hoover Dam, which are effectively bookends for the

Grand Canyon. As the water master for much of the river corridor,

Reclamation is charged with advancing sound management of this

essential resource.

Broad water conflicts began to emerge in the Colorado River basin

in the early 1900s. Over the century that followed, entities associ-

ated with the river struck numerous compacts, treaties, settlements

and other agreements – some amicably and some through hard-

fought litigation. Collectively, these comprise the ‘Law of the River’.

The core of the Law of the River is a series of apportionments within

the United States, and between the United States and Mexico, which

date back over half a century. Unfortunately, these

agreements were based on a limited flow record that

does not reflect the river’s long-term average annual

yield. As apportionments continued to develop, sizeable

dams and their associated reservoirs were constructed

along the river to buffer the significant variability in

year-to-year flow. Since the early 1950s, there have been

a number of years when the annual water use in the

Colorado River basin exceeded the yield; these short-

ages were avoided only through the stored water. In this

regard, the Colorado River is unique – the river’s total

storage capacity is about four times the mean annual

natural yield of the river basin.

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The Colorado River basin

Source: Bureau of Reclamation