A Disappearing Lake

In the article “Nevada's Lake Mead, the water history scare factor” on Digital Journal, journalist Jay David Murphy argues that the current wave of worry and fear about water levels in Lake Mead, which provides “Las Vegas and southern Nevada with 90% of its useable water” are unfounded. He cites historical water levels, as far back as 1937, to demonstrate the natural fluctuations that occur. Murphy claims that this recent drop in level s in merely part of a natural cycle. As he says “Lake Mead has kept consistent water level since 1935. It has fluctuated about a 150 feet up and down, but remained remarkably consistent”. Murphy insists that in fact politicians are encouraging new fears of Lake Mead drying up to hide the fact that there would never be enough water in it to satiate demand, as they had promised.
Murphy does provide a link to the U.S. Department of the Interior’s Bureau of Reclamation where water levels for Lake Mead can be found and the fluctuations that he describes can be observed. However, the current level doesn’t seem to be as normal as he insists. Right now, Lake Mead is at 1,093 feet-- its lowest since 1965. According to the government of Nevada’s policy, if the water level drops to 1,050 feet, the authorities will cut off one of the water mains that run to Vegas. Murphy doesn’t seem worried by this stating that “other than pre-1937 (when the Hoover dam that created the lake was built) it has never been that low”. However, this is where the flaw in Murphy’s argument for natural cycles becomes obvious. One cannot base the argument that low water levels now are part of a natural fluctuation on the fact that ‘it’s always returned back to normal levels in the past’. Doing this would be equivalent of looking at Lake Mead as an isolated entity, separate from the rest of the world which is not being affected by climate change, or increased water demands.
Lake Mead is fed by the Colorado River, which in turn is fed by snow run-off from the Rocky Mountains. In their article “When Will Lake Mead Go Dry?” (2008), Barnett and Pierce cite several studies from the last 20 years that proposed that this run-off will decrease in the future due to climate change. This is due to a decrease in precipitation and an increase in temperatures and evapotranspiration. They go on to elaborate on their own study which suggests that if current water consumption habits continue “there is a 10% chance that the live storage (the amount of water that can be taken out of the lake by gravity) in the lake will be gone by 2013 and a 50% chance that it will be gone by 2021” (Barnett and Pierce, 2008). The changes in run-off are ones that have never been seen before, and so we cannot use historical data to determine how the lake’s water levels might be changed by them. This is not part of the normal cycle of the lake’s water levels, this is something new and different. Therefore, Murphy is erroneous in claiming that “the numbers prove” that Lake Mead is in no danger of drying up—this is a weak and poorly supported argument.
-Olivia Mussells
References

Barnett, Tim P. & David W. Pierce (2008). When will Lake Mead go dry?
Water Resources Research, 44:1-10.

Murphy, Jay David. (2009) Nevada’s Lake Mead, the water history scare factor. Digital Journal,
23 Sept 2009. http://www.digitaljournal.com/article/279596. Accessed 25 Sept 2009.