Cities such as Phoenix and Las Vegas continue to expand at a mind-boggling rate, adding thousands of new residents every month. But the amount of water the river delivers in a given year - around 15 million acre-feet - remains unchanging and finite.
Given that growing discrepancy, some are now calling for a new paradigm in approaching growth issues in the region. Essentially, an attorney and a law professor told the Colorado River Water Users Association conference on Thursday, that the time may have arrived to label these and other Western boomtowns mature communities that need stabilization and enhancement - as opposed to continued immigration from the outside.
Land-use attorney Grady Grammage Jr., a former president of the Central Arizona Project board, calls the current status quo in the West irrational, largely because the issues of water and growth planning have historically been kept separate. That, he said, has to end.
There is a relationship between growth in the West and water supplies, he told the gathering of Western water officials. If you don't start talking about it, you're going to lose control of it - either in the courts or at the ballot box.
The public, he noted, is most definitely thinking and talking about it, and is confused by the mixed messages being sent by political leaders. People are being told that there's not enough water to brush their teeth like they want to, then they wonder why you're approving new developments, Grammage said.
The ongoing battle over who gets what out of the Colorado River is a case in point. The lower basin states of California, Arizona and Nevada have developed most, if not all of their water resources from the river, yet continue to be a magnet for transplants from the East, Midwest and south of the border.
That, in turn, leads to an upward spiral in government growth projections, which University of California at Berkeley law professor Antonio Rossman says eventually becomes a self-fulfilling prophecy.
But a recent ruling by the California Court of Appeal has challenged those notions, he told the audience, rejecting the state's environmental assessment of a bay-delta improvement program, which would have increased water supply.
The project's proponents argued that the state's 60 percent population growth projection by 2020 necessitated its development.
But the court wondered, Rossman said, that if there is no water to support the growth, will it occur as projected? Population growth is not an immutable fact of life.
The question, Rossman added, is not whether we have the power to influence future population patterns, but whether we want to attempt its exercise.
Such pronouncements make officials from the upper basin states - Utah, Colorado, Wyoming and New Mexico - uncomfortable. Mainly because the upper basin states believe they still have plenty of room to grow.
This is a legitimate issue in the lower basin because they have developed all of their water, said Larry Anderson, director of the Utah Division of Water Resources, but the upper basin has not.
In Utah, 60 percent of our growth is internal, he added. If we don't develop resources like the Lake Powell pipeline, will it just push the population somewhere else in the state?