the region remains the destination of choice for the millions of people who annually visit. According to a study by Protect the Flows, a coalition of more than 400 small businesses throughout the seven states, river-related recre- ation supports 234,000 jobs in Arizona, Colorado, Nevada, New Mexico, Utah and Wyoming and produces $26 billion in economic output.
“The Study makes it clear just how much the Colorado River needs to watch its bottom line,” said Molly Mugglestone, Protect the Flows coor- dinator. “The West’s economic future is tied to this magnificent resource and the recreation it encourages, so we would do well to do all we can to pro- tect it and to keep the river flowing.” This issue of Western Water exam- ines the Colorado River Basin Water Supply and Demand Study and what its finding might mean for the future of the lifeblood of the Southwest.
Informing the Basin’s Future In 2009, Reclamation selected three river basins, including the Colorado, for its Basin Study Program. The Study’s goal was “to complete a comprehensive review of water supply and current and long-term demands through 2060, assess options for resolv- ing water supply imbalances and to develop recommendations for future consideration to address current and projected imbalances.” The Study is for planning purposes and will not result in the selection or funding of a particular proposed option. Rather, the Study is intended to explore a broad range of options to help address future imbalances.
Given the historical variability of Colorado River flows and the potential for increased variability in the future, there is great uncertainty associated with future water supply throughout the Basin over the next 50 years. That uncertainty, coupled with the un- certainty in future demand for water Basin-wide, is being addressed using a scenario planning approach. The Study has six demand scenarios and four supply scenarios that together
November/December 2012
produce a range of projected imbal- ances. “The concept was to basically look at demand projections, supply projections and apply some kind of litmus test to it in terms of reliability, sustainability and then solicit ideas and thoughts how to correct any imbal- ance,” Moore said.
There are more than 2,000 possible futures represented by the four water supply scenarios. In general, the four scenarios are: • Future hydrologic trends and vari- ability modeled on the recorded history, approximately the past 100 years, of streamflow.
• Future hydrologic trends and vari- ability represented by reconstruction of the paleo record of streamflow – a reconstructed record of the past 1,250 years.
• Future hydrologic trends and vari- ability represented by a blend of the wet-dry states of the longer paleo- reconstructed period (nearly 1,250 years), but magnitudes are more similar to the observed period (about 100 years).
• Future hydrological trends altered by a future climate that will continue to warm.
Pitt noted the Study reveals that the pool of available water for Colorado River users will decline and will be the determining factor of future manage- ment. “A point we don’t want to over- look is if you look at the relative impact of demand and the relative impact of supply based on climate change, supply appears to be a much bigger driver in the gap than demand,” she said. Several supply augmentations options have been identified and they range in size, scope and expense. Moore said there are projects that could be built in California or Mexico where seawater desalination “could supply a very large quantity of water,” that would help manage the demand curve. From the watershed management perspective, experts have identified ways to conserve water through brush and forest management (including tamarisk control) and dust mitiga- tion. Desert dust kicked up by human