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Brian Fowler | September 15th, 2015

 

Every year, millions of tourists from across the country visit the famed Colorado River for its many recreational opportunities, including motor-boating, fishing, and rafting. One of the most popular destinations is Glen Canyon Reservoir, otherwise known as Lake Powell. Surrounded by beautiful red rock cliffs and breathtaking geologic formations, the reservoir’s unnaturally emerald-green waters stretch from the Utah-Arizona border all the way to the bridge at Hite Crossing over a hundred miles to the northeast. For its many aesthetic charms and laid-back atmosphere, visitors affectionately refer to Lake Powell as the Jewel of the Colorado River. But alarmingly, this jewel could disappear over the coming decades as a result of the regional effects of climate change and the Southwest’s increasing demand for water.

Lake Powell’s walls can talk; the sandstone cliffs and the reservoir’s fifty-nine year history of changing water levels tell the story of the arid west’s disappearing water resources. Over the last two decades, visitors have observed that the reservoir’s water level has dropped sharply. A white line, made up of exposed calcium carbonate deposits, runs along the walls of Glen Canyon Reservoir. This line, known locally as the “bathtub ring,” marks how far Lake Powell’s water levels have fallen over the years.

Historical data support the conclusions made by casual observations of the bathtub ring. As of April 2015, Lake Powell was at only 45% capacity.1 This low water volume is part of a seventeen year trend. Evidence compiled by EcoWest shows that, since 1998, water levels have been significantly below the historical average; since 2011, the reservoir’s surface has fallen over 50 feet.2

Unfortunately for the 40 million people who depend on the Colorado River as their primary water source, this trend of decreasing water availability will likely continue for several decades, if not indefinitely. Climate projections for the already dry Southwest predict a drop in precipitation, as well as an almost certain increase in evaporation caused by higher temperatures.3 If these projections are accurate, the water level in Lake Powell could eventually reach dead pool, a level so low that water cannot escape the reservoir by natural gravity alone. Dead pool would not only mark the end of Glen Canyon Dam’s electric power generation, it would also expose a layer of toxic sediments that have been accumulating below the water since the dam was completed. The Colorado River’s red sediment contains trace amounts of heavy metals. When the Bureau of Reclamation built Glen Canyon dam, that sediment began to build up behind its concrete wall. If the dam’s managers continue to release water downstream at current levels, the jewel of the Colorado could be transformed into a stagnant pool loaded with decades of accumulated heavy metals.

Although it was inevitable that Lake Powell would one day fill with sediment, the Bureau of Reclamation expected the process to take hundreds of years. However, given projected changes to the region’s climate regime, the toxic layer of chemicals could surface in decades rather than centuries.

Currently, Page, Arizona, population 8,000, is the only city that takes water directly out of Lake Powell. The rest of the water is channeled through hydropower turbines and released downstream. That situation could change in the coming years as other desert cities try to stick a new straw into the lake. One such proposal calls for the construction of a 139 mile pipeline to transport water across the state of Utah, at a projected cost of $1 billion.4 Such projects are politically ambitious and extraordinarily expensive, but as water supplies dwindle, and nearby cities like St. George, Utah, continue to grow, Glen Canyon Reservoir will look like an ever-more attractive resource to the region’s water-strapped municipalities. There is no guarantee that the pipeline will be built, but if it were the likelihood of Lake Powell reaching dead pool would only increase as the Southwest’s changing climate continues to take its toll on water levels.

Beyond the local problems that dead pool would cause, the falling water levels have chilling implications for the rest of the southwestern region and everyone else who depends on the Colorado River. Much like the Down Jones Industrial Average compiles information from many economic sectors to create a simplified indicator of how the entire economy is performing, Lake Powell indicates how the entire Colorado River basin is performing in terms of water supply.2 The reservoir’s level depends on the amount of precipitation, both rain and snow, that falls in the upper basin states of Wyoming, Utah, and Colorado. All of the Colorado’s upper basin tributaries, whose water levels are difficult to measure, combine to make a complex river system that eventually coalesces into Glen Canyon reservoir. Water released from Glen Canyon Dam runs downstream to the lower basin (Arizona, Nevada, and southern California) which receives far less precipitation. If less precipitation falls in the upper basin, then Lake Powell’s level will drop, meaning that less water will be available for use in the lower basin. The low water levels that have been recorded for Glen Canyon Reservoir over the last decade indicate a combination of low precipitation in the Rocky Mountains and high rates of evaporation on the reservoir and on the Colorado.

Population growth in the American Southwest has been underpinned by the assumption that there would always be plenty of water for everyone. The 40 million people who rely on the Colorado River for drinking water will have to challenge their old assumptions as a new climate regime significantly decreases water availability. The dream of endless development and population growth will soon come to an end as the region wakes up to its new, water-scarce reality. Glen Canyon’s bathtub ring is irrefutable evidence of how precarious the water situation in the arid southwest will be over the coming decades. If Southwesterners want to maintain their livelihood in the great American desert, they will have to change their mindset from one of expansion to conservation.

References

1. Taylor A. 2 April 2015. The American West Dries Up. The Atlantic. [Internet] [Cited 2015 Sep 14]. Available from: http://www.theatlantic.com/photo/2015/04/the-american-west-dries-up/389432/

2. Tobin M. 21 Aug 2013. Plotting “dead pool” and other watersheds for Lake Powell and Lake Mead. EcoWest. [Internet] [Cited 2015 Sep 14]. Available from: http://ecowest.org/2013/08/21/plotting-dead-pool-and-other-watersheds-for-lake-powell-and-lake-mead

3. Seager R, Ting M, Held I, Kushnir Y, Lu J, Vecchi G, Naik N. 2007. Model projections of an imminent transition to a more arid climate in southwestern North America. Science 316(5828): 1181-1184.

4. O’Donoghue A. 29 Nov 2013. Lake Powell Pipeline gets financing reality check. Desert News. [Internet] [Cited 2015 Sep 14] Available from: http://www.deseretnews.com/article/865591561/Lake-Powell-Pipeline-gets-financing-reality-check.html?pg=all