Unexpected Surge in Lake Mead Storage May Cause Backlash

I’d wager that the environmental issue that draws the most attention and concern in the Southwest is water and its dwindling supplies.

Water supply is also the issue that directly links climate to human welfare for most people in the Southwest. More than 30 million people tap the Colorado River in seven U.S. states and Mexico. When it doesn’t rain or snow and when warmer temperatures increase evaporation, the water elevation drops closer to 1,075 feet above sea level, the ominous threshold that if breached will force rationing in states in the Lower Basin—Arizona, California, and Nevada. As of October 1, the water elevation hovered only 9 feet above 1,075, and forecasts for a dry winter forebode further declines.

The media often calls attention to the falling elevation of Lake Mead, the lower of the two main reservoirs that store water on the Colorado River. “Drought has Lake Mead at Historic Low” was a November 1 headline for the Arizona Daily Star. In August the New York Times issued the warming “Lake Mead's Water Level Plunges as 11-Year Drought Lingers.” I suspect many people—not just the media—focus on the water elevation in Lake Mead as a surrogate for drought. I also believe that Lake Mead’s storage is the fulcrum that will force people to take climate change seriously. The potential pitfall with these impressions is that water elevation in Lake Mead is also determined by Lake Powell, the large upstream reservoir. It’s possible that this year the Southwest could receive scant rain and snow, which will cause drought conditions to expand, yet Lake Mead’s water level could actually increase because of an extra slug of water from Lake Powell. If this scenario were to occur, it would mask the persistence of water supply challenges and the impacts of climate change.

The more complete picture of how Lakes Mead and Powell are managed is propounded in the Bureau of Reclamation’s (BOR) Environmental Impact Statement issued in 2007. This document outlines guidelines for managing lakes Mead and Powell together under drought conditions. Under these guidelines, Lake Powell would release additional water to Lake Mead if water level forecasts in April suggest that on September 30 Lake Mead levels will fall below 1,075 feet and Lake Powell water levels are above certain thresholds. The recent October forecast issued by BOR suggests a 50 percent probability that Lake Powell will release more than 10.7 million acre-feet (MAF) in late 2011, about 2.5 MAF more than average. This extra pulse would have the effect of increasing the water level in Lake Mead by about 25 feet and delaying water rationing. However, this extra dollop may only be a one-time addition. Lake Mead only gets extra water if ample water is stored in Lake Powell. Every year the storage threshold in Lake Powell increases so that more and more water has to be in Lake Powell for the extra slug to be released to Lake Mead.

If people are not aware that under drought conditions Lake Mead and Lake Powell are managed as one unit, it is likely that the sirens currently ringing will disappear, and worse, give people the perception that the problems were manufactured by doomsayers. They may be reminded of the boy who cried wolf.

The bottom line is, don’t be surprised if sometime soon Lake Mead’s water levels surge. Even if headlines about imminent shortages disappear, there still exists a clash between expanding population, limited water supplies, and likely additional losses due to climate change. At some point the wolf will arrive. 

More information:

If you are interested to learn more about joint management of Lakes Powell and Mead, visit the BOR site and click on the Record of Decision Link.

Also, read about projections of future Lake Powell releases to Lake Mead.