Amid a once-in-a-millennium prolonged drought fuelled by the climate crisis, one of the largest water distribution agencies in the United States is warning six million California residents to cut back their water usage this summer, or risk dire shortages.

The scale of the restrictions is unprecedented in the history of the Metropolitan Water District of Southern California, which serves 20 million people and has been in operation for nearly a century.

Adel Hagekhalil, the district’s general manager, has asked residents to limit outdoor watering to one day a week so there will be enough water for drinking, cooking and flushing toilets months from now.

“This is real; this is serious and unprecedented,” Hagekhalil told Al Jazeera. “We need to do it, otherwise we don’t have enough water for indoor use, which is the basic health and safety stuff we need every day.”

The district has imposed restrictions before, but not to this extent, he said. “This is the first time we’ve said, we don’t have enough water [from the Sierra Nevadas in northern California] to last us for the rest of the year, unless we cut our usage by 35 percent.”

Depleted reservoirs

Most of the water that southern California residents enjoy begins as snow in the Sierra Nevadas and the Rocky Mountains. The snowmelt runs downstream into rivers, where it is diverted through reservoirs, dams, aqueducts and pipes.

For most of the last century, the system worked; but over the last two decades, the climate crisis has contributed to prolonged drought in the west – a “megadrought” of a scale not seen in 1,200 years. The conditions mean less snowfall, earlier snowmelt, and water shortages in the summer.

California has enormous reservoirs, which Hagekhalil likens to a savings account. But today, it is drawing more than ever from those savings.

“We have two systems – one in the California Sierras and one in the Rockies – and we’ve never had both systems drained,” Hagekhalil said. “This is the first time ever.”

John Abatzoglou, an associate professor who studies climate at the University of California Merced, told Al Jazeera that more than 90 percent of the western US is currently in some form of drought. The past 22 years were the driest in more than a millennium in the southwest.

“After some of these recent years of drought, part of me is like, it can’t get any worse – but here we are,” Abatzoglou said.

The snowpack in the Sierra Nevadas is now 32 percent of its typical volume this time of year, he said, describing the warming climate as a long-term tax on the west’s water budget. A warmer, thirstier atmosphere is reducing the amount of moisture that flows downstream.

The dry conditions are also creating a longer wildfire season, as the snowpack moisture keeps vegetation wet enough to resist carrying fire. When the snowpack is low and melting earlier in the year, vegetation dries out faster, allowing flames to sweep through the forests, Abatzoglou said.

‘Significant imbalance’

With less water available from the northern California snowpack, Hagekhalil said the district is relying more on the Colorado River. “We’re lucky that in the Colorado River, we have built in storage over time,” he said. “That storage is saving the day for us right now.”

But Anne Castle, a senior fellow at the University of Colorado’s Getches-Wilkinson Centre, said the river that provides water to communities across the west is experiencing another “extremely dry” year. The river, which flows southwest from Colorado to the northwestern tip of Mexico, is fed by the snowpack in the Rocky Mountains and the Wasatch Range.

Two of the largest reservoirs in the US are at critically low levels: Lake Mead is about a third full, while Lake Powell is a quarter full – its lowest level since it was first filled in the 1960s. Lake Powell is so parched that government agencies fear its hydropower turbines could become damaged, and are mobilising to divert water into the reservoir.

Over the past 22 years, the Colorado River system has seen a “significant imbalance” between supply and demand, Castle told Al Jazeera. “Climate change has reduced the flows in the system in general, and our demand for water greatly exceeds the reliable supply,” she said. “So we’ve got this math problem, and the only way it can be solved is that everybody has to use less. But allocating the burden of those reductions is a very tricky problem.”

In the short term, Hagekhalil said, California is working with Nevada and Arizona to invest in conserving water and reducing consumption – but in the long term, he wants to transition southern California away from its reliance on imported water and instead create a local supply. This would involve capturing rain, purifying wastewater and polluted groundwater, and recycling every drop.

What worries him most about the future of water in California, however, is that people have short memory spans: “We’ll get heavy rain or a heavy snowpack, and people will forget that we were in this situation … I will not let people forget that we’re so dependent on the snowpack, and we can’t let one day or one year of rain and snow take the energy from our building the resilience for the future.” (Al Jazeera)

•PHOTO: An aerial drone view showing low water near the Enterprise Bridge at Lake Oroville in Butte County, California where water levels are less than half of its normal storage capacity [Kelly M Grow/California Department of Water Resources]

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