The National Park Service announced on Sunday (August 7, 2022) the unsettling discovery of human skeletal remains at the Lake Mead National Recreation Area – but why is the lake drying up to reveal these horrors?
Yesterday’s news marks the fourth set of human remains to emerge from the lowering water levels.
The other bodies were discovered on May 1, May 7 and July 26. The UK’s MailOnline reports a man named Todd Kolod believes the second set of remains to have been his late father’s.
From an environmental perspective, why is the lake’s water level so low?
Why is Lake Mead drying up?
There are three primary reasons Lake Mead is drying up: too much extraction, too much heat, and too little snowmelt.
Its water level has dropped a startling 170ft (52m) since 1983, reports The Guardian, and officials predict the level will continue to fall.
The lake has been below full capacity since that year and, as of August 7, 2022, holds little more than a quarter (27.36 per cent) of what it could hold.
So far in 2022, a total of 6.46 million acre-feet has flown into Lake Mead, while almost 8 million acre-feet have flown out. An acre-foot is about the same as an eight-lane swimming pool – 82ft (25m) long, 52ft (16m) wide and 9.8ft (3m) deep. Or, if it’s easier to think of it a different way, it’s about enough to cover a football field in 1ft of water.
Why is it so significant Lake Mead is drying up?
Lake Mead is the largest reservoir in the US in terms of water capacity. It provides water to Arizona, California and Nevada, plus parts of Mexico.
It sustains close to 20 million people, according to Eco Watch, which, incidentally, published a report in 2015 about the “historic low” Lake Mead had reached that year. The Australian Broadcasting Corporation, meanwhile, writes pointedly that “the demands of 40 million people in seven states […] are sucking the Colorado river dry.”
You may remember 2015 was the hottest year on record.
The Conversation wrote in January 2016 that the National Oceanic and Atmospheric Administration had confirmed 2015 had seen the global average temperature climb almost a full degree celsius above the 20th century average of 13.9.
How much water evaporates from the reservoir each year?
Reservoirs are most important in places where water is scarce. And water scarcity often goes hand in hand with persistent hot weather.
The temperature around Lake Mead fluctuates a lot through the year but one thing people travel to the National Recreation Area for is its good weather. NPS calls it “the land of the sun,” and one thing the sun does is cause water to evaporate.
As of December 2008, according to the United States Bureau of Reclamation, about 800,000 acre-feet evaporate from Lake Mead every year.
Obviously picturing water in acre-feet doesn’t come naturally to most people. But if you can imagine it, that’s the same as 800,000 eight-lane swimming pools disappearing from the waters of Lake Mead every year. Or 800,000 football pitch-feet.
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Snowmelt and Lake Mead’s water levels
Snowmelt contributes a lot of water to Lake Mead – perhaps more than you’d expect.
For example, a particularly heavy snowmelt in the Rocky Mountains during the second half of 2011 prompted the release of a whopping 3.3 million acre-feet (4.1 million megaliters) from Glen Canyon into the reservoir.
According to Earth Observatory, about 10 per cent of Lake Mead’s water comes from rain and groundwater, with the rest coming from snowmelt in the Rocky Mountains.
However, climatologist Russ Schumacher told the Ark Valley Voice in April this year the southwest US as a whole has been in a “dry period” since 2000. That’s 22 years. And persistent dry weather doesn’t bode well for future snowmelts – the snow itself has to come from somewhere.