Lakes at all-time low, early forest fires, water restrictions and now potentially record-breaking heat wave: summer has yet to officially begin and the western United States is already feeling the full brunt of the effects chronic drought, further exacerbated by climate change.
According to the latest records from government agencies, 88% of the American West was in a state of drought this week, including all of California, Oregon, Utah and Nevada.
The latest symptom to date of this phenomenon, which affects a total of more than 143 million people in the United States, Lake Mead, the country’s largest water reserve located on the Colorado River, on the border of Nevada and the United States. Arizona, this week hit its lowest level since its inception in the 1930s.
The lake, adjacent to the famous Hoover Dam which stands at the gates of Las Vegas, is only 36% full, below the record set in 2016. Federal authorities certainly expected a such shortage occurs, but not before August.
The situation is equally worrying in northern California, which is generally well watered during winter and spring. The level of Lake Oroville, the state’s second reservoir and a key element in the network providing drinking water to 27 million Californians, is fifty meters lower than in 2019.
From now on, severe water restrictions are inevitable in the coming months, which could have serious consequences in several states in the west of the country, especially for farms that depend on irrigation and provide much of the water. fruits and vegetables of the country. Not to mention the California almond trees, which account for up to 80% of world production but which some farmers have already started to pull out to reduce their water consumption.
As of April 1, which traditionally marks the end of snowfall, snow reserves in the neighboring Sierra Nevada – the source of about a third of the water used in California – were only about 60% of the average. .
“What is really unique this year is that when the snow melted, the runoff ended up seeping into the dry soils and evaporating”, without actually reaching Lake Oroville to swell its reserves, John Yarbrough, an official with the California Department of Water Resources, told AFP.
– “Rare, dangerous and deadly” –
According to the Drought Observatory, a third of California is currently experiencing “exceptional drought”, the most severe stage.
However, these arid soils and parched vegetation in turn create the conditions for an increase in temperatures, setting up a devastating vicious circle.
Unsurprisingly, the southwestern United States is bracing for an extreme heat wave next week, with temperatures at least 11 ° C above seasonal averages and risking to approach 50 ° C in places.
Las Vegas could thus beat the heat record established in 1940, with a temperature of up to 46 ° C next Wednesday, according to the weather services which launched an alert in various states.
Such conditions are “rare, dangerous and fatal,” warned National Weather in Phoenix, central Arizona.
The authorities fear in particular a resurgence of forest fires, which were particularly early and intense this year: at the end of May in California, the fires had already consumed five times more vegetation than last year at the same time.
For most experts, even though the southwestern United States is naturally prone to drought, there is no doubt that the situation is significantly worsened by global warming.
A study published last year in the journal Science estimated that climate change induced by human activities had accentuated the impact of drought by 46% between 2000 and 2018.
“What is clear is that we are already living in a new climate, a climate which is different from the one our systems were designed under fifty or a hundred years ago,” Noah Diffenbaugh, climatologist at AFP, told AFP recently. Stanford University of California.
“And it is a climate in which water deficits are mainly the consequence of warming”, estimates the expert, for whom it remains possible “to manage the risks presented by these climate changes”.
“But to achieve this, we must not only recognize the reality of this climate change and adjust to it, we must anticipate,” he underlines.