From Dr. Roy Spencer’s Global Warming Blog
August 24th, 2022 by Roy W. Spencer, Ph. D.
UPDATED: Fixed Bureau of Reclamation study link, added Colorado River basin snowpack graph and discussion.
In today’s news is yet another article claiming the record-low water levels in Lake Mead (a manmade water reservoir) are due to human-caused climate change. In fact, to make the problem even more sinister, the Mafia is also part of the story:
Climate change is uncovering gruesome mafia secrets in this Las Vegas lake
While it is true that recent years have seen somewhat less water available from the Colorado River basin watershed (which supplies 97% of Lake Mead’s water), this is after years of above-average water inflow from mountain snowpack. Those decadal time-scale changes are mostly the result of stronger El Nino years (more mountain snows) giving way to stronger La Nina years (less snow).
The result is record-low water levels:
Lake Mead water levels since the construction of Hoover Dam (source: NBC News)
But the real problem isn’t natural water availability. It’s water use.
The following graph shows the fundamental problem (click for full resolution). Since approximately 2000, water use by 25 million people (who like to live in a semi-desert area where the sun shines almost every day) has increased to the point that more water is now being taken out of the Lake Mead reservoir than nature can re-supply it.
This figure is from a detailed study by the U.S. Bureau of Reclamation. As long as that blue line (water supply) stayed above the red line (water use), there was more than enough water to please everyone.
But now, excessive demand for water means Lake Mead water levels will probably continue to decline unless water use is restricted in some way. The study’s projection for the future in the above figure, which includes climate model projections, shows little future change in water supply compared to natural variability over the last century.
The real problem is that too much water is being taken out of the reservoir.
As long as the red line stays above the blue line, Lake Mead water levels will continue to fall.
But to blame this on climate change, whether natural or anthropogenic, ignores the thirsty elephant in the room.
UPDATE: Since it was pointed out in comments (below) that the latest Bureau of Reclamation study is rather dated (2012), and supposedly the drought has worsened since then, here’s a plot of the Colorado River basin April (peak month) snowpack, which provides about 50% of the water to Lake Mead. The rest is provided in the non-mountainous areas of the river basin, which should be highly correlated with the mountainous regions. I see no evidence for reduced snowpack due to “climate change”… maybe the recent drought conditions are where the demand by 25 million water consumers originates from, causing higher demand?
April snowpack in the Colorado River basin, the greatest source of water input to Lake Mead (data from https://www.nrcs.usda.gov/Internet/WCIS/AWS_PLOTS/basinCharts/POR/WTEQ/assocHUCco_8/colorado_headwaters.html