The
Compact and Lees Ferry
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." The most
important of these is the Colorado River Compact (hereafter, the
“Compact”).
In 1922, the
Compact was negotiated by the seven Colorado River Basin states
and the federal government. It defined the relationship between
the upper basin states, where most of the river's water supply
originates, and the lower basin states, where the demand for water
was growing fastest at the time. One of the main motivations for
the Compact was California's interest in plans for Boulder Canyon
(Hoover) Dam and other water development projects in the lower
basin that could, under the Western water law doctrine of prior
appropriation, later deprive upper basin states like Colorado
and Utah of their ability to use the river's flows in the future.
The Compact
established Lees Ferry, Arizona as the dividing point between
the upper basin (Colorado, Wyoming, Utah, and New Mexico) and
the lower basin (California, Nevada, and New Mexico). The Compact
effectively split the flow of the river at Lees Ferry in half,
with 7.5 million acre-feet (MAF) per year apportioned to the upper
basin, and 7.5 MAF apportioned to the lower basin. The upper basin,
being upstream, was given the responsibility of delivering*
the lower basin’s allotment. A treaty between the U.S. and
Mexico in 1944 further allocated 1.5 MAF per year to Mexico.
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Map
of the Colorado River basin showing Lees Ferry (black
dot at center) and the division (light dotted line) between
the Upper and Lower basins.
Map
courtesy of the U.S. Bureau of Reclamation
|
| "Lee
Ferry" and "Lees Ferry"
Lee Ferry and Lees Ferry are actually
distinct locations on the river, only one mile apart.
Both are named for pioneer ferry operator John D.
Lee. Lee Ferry is the point on the river on the hydrologic
divide between the upper and lower basins, and is
used as the measurement point for the allocation between
the two basins. Lees Ferry, about a mile upstream
of Lee Ferry, is the location of the U.S. Geological
Survey's stream gage. (The gage could not be installed
at Lee Ferry for logistical reasons.) The Paria River
enters the Colorado River between Lees Ferry and Lee
Ferry, so its gaged flow is added to the Lees Ferry
gaged flow to measure the upper basin's total delivery
to the lower basin.
To avoid confusion,
we will use "Lees Ferry" to refer to both
locations, although this is slightly inaccurate with
respect to the Compact.
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In total,
the Compact and later treaties apportioned 16.5 MAF per year of
the river’s flow at Lees Ferry (though there is contention
about whether an additional 1.0 MAF allocated to the lower basin
was intended to come from the mainstem or lower basin tributaries--if
the former, then the total apportionment at Lees Ferry is 17.5
MAF). The Compact’s negotiators believed that the average
flow at Lees Ferry was about 16.4 MAF, based on the 20 years of
gage records available in 1922. However, the flow since 1922 has
been generally lower than these early gaged flows, and the long-term
mean gaged flow at Lees Ferry (1906-2004) is about 15.1 MAF. In
other words, the Colorado River has been over-allocated. There
is not enough water in the river, on average, to fulfill all of
the legal entitlements.
This overallocation
has not yet led to major conflicts or forced any curtailments
of use, largely because the upper basin has historically used
much less than their full share of the river. But the upper basin’s
use has been increasing along with population, especially in Colorado.
Also, the completion of the Central Arizona Project (CAP) in 1993
brought Arizona's use up to its full allocation. Then, beginning
in 2000, a severe and persistent drought has challenged the system
more than any previous drought. The combination of higher usage
in the upper basin and low natural runoff led to very low inflows
into the major reservoirs. Lake Powell dropped to one-third of
its capacity, and the threat arose of a Compact-driven curtailment
of upper basin uses in order to deliver the lower basin’s
full share.
On
to...the Lees Ferry gaged
flow record.
*The language
of the Compact does not actually use the word "deliver".
Instead, it specifies that the upper basin shall "not deplete"
the flows of the Colorado below that necessary for 75 MAF in a
10-year period (or an average of 7.5 MAF per year) to pass downstream
to the lower basin.
