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July 9th, 2021
Via Washington Post, an article on the dire state of US reservoirs as consequences of the Western drought worsen:
Reservoir levels are dropping throughout the West, as the drought tightens its grip on the region and intense summer heat further stresses both water supply and the surrounding landscape. Many reservoirs are at or approaching historic low levels due to lackluster rainy seasons combined with increasing temperatures due to climate change.
The drought crisis is perhaps most apparent in the Colorado River basin, which saw one of its driest years on record, following two decades of less-than-adequate flows. The nation’s largest reservoir, Lake Mead near Las Vegas, is at its lowest level since the lake filled after the construction of the Hoover dam in the 1930s; it currently sits at 1,069 feet above sea level, or 35 percent of its total capacity. It supplies water to Arizona, Nevada, California and Mexico.
Further upstream, Lake Powell, which feeds Lake Mead, is at only 34 percent of its total capacity. By next spring, Lake Powell is projected to hit its lowest level since it was filled in 1964, possibly jeopardizing its ability to generate power.
California’s two largest reservoirs, Lake Shasta and Lake Oroville, are on track for potential record lows this summer, now at 37 percent and 31 percent of their total capacities, respectively.
Amid a warm spring and early-season heat, mountain snowpack never made it into rivers and reservoirs — it simply seeped into bone-dry soils or sublimated directly into the atmosphere. This kind of reduced runoff “efficiency” is expected in a warming climate, and it contributed to the quickly intensifying drought this year in California and other states.
“The reservoir levels in the second year of this drought are what they were during the third or fourth year of the previous drought,” said Jay Lund, a professor and water resources expert at the University of California at Davis.
“Certainly, many reservoirs in the state will see levels lower than they’ve seen since 1976-77, maybe even lower,” said Lund, referring to California’s driest water year on record.
Lund said to expect a wide range of impacts from low reservoirs this summer, including reduced hydropower production and reduced water deliveries to agriculture, fish and urban areas downstream.
Impacts will accumulate through the summer
The Western United States entered a months-long dry season already in severe drought, and then extraordinary heat bore down on the region in June, meaning that reservoirs, soils and plants are losing even more water through evaporation. With climate change pushing heat to new and more frequent extremes, it’s a safe bet that the coming months will feature more of the same. In fact, another major heat wave is descending upon California and the West this weekend.
Both the drought and its impacts are intensifying at a rapid pace. While these were felt first and most acutely by ranchers who rely on nonirrigated pastures, they have quickly expanded to other sectors as reservoir operators curtail water releases.
The term “shortage” is now both a projection from government agencies and a reality for communities, farmers and ranchers.
In August, a shortage will likely be declared for Lake Mead, which will trigger substantial cuts in water deliveries to Arizona, Nevada and Mexico next year to slow further losses.
California’s vast reservoir network, the State Water Project, is delivering only 5 percent of requested supplies to its 40,000 water rights holders, which is sending reverberations throughout the state. In June, the City of San Jose became the largest urban area to impose water restrictions so far this year, with Santa Clara County declaring a water shortage emergency.
The drastically reduced deliveries from the state have also directly affected farmers, and by extension, smaller communities that rely on well water. Shallow wells are drying up as farms draw more heavily on groundwater; one Central Valley community has already run dry and is importing bottled water for basic needs, Cal Matters reports.
On Thursday, Gov. Gavin Newsom (D) expanded drought emergency status to 50 of the state’s 58 counties. He asked Californians to voluntarily cut water use by 15 percent but did not issue mandatory statewide restrictions.
Faith Kearns, a scientist at the California Institute of Water Resources, said many communities face chronic water supply issues that are exacerbated by drought and groundwater withdrawal.
“My biggest concern is always with ensuring that people have affordable clean water at the household level, and that ecosystems and the life they support can manage,” she wrote in an email. “It’s already a struggle that will continue to worsen throughout the dry season.”
In the Klamath River watershed on the Oregon-California border, record low inflows are threatening fish both in reservoirs and downstream, while reduced reservoir releases are cutting off water to farmers. The region is already seeing fish die-offs from low stream levels and warm water temperatures.
Some parts of the West, such as Southern California, are better prepared than others, having boosted backup water sources and enacted conservation measures during the last drought that are paying dividends today. But that doesn’t mean the state has solved its water woes.
“We are still facing many of the same issues we have been for a long time, including dwindling fish populations and drying wells,” Kearns wrote. “That to me indicates that we still have a long way to go.”
When will the drought end?
Even after this summer, rains may not arrive as hoped, and it will probably take more than one good wet season to replenish water lost through missed precipitation and increased evaporation.
“After having been through many more drought years than not over the last decade, I am starting to wonder if we should even be using the term drought,” Kearns said.
Over the last 20 years, human-caused warming has intensified what would have been an ordinary dry period in the Southwest into a potential “megadrought” — in some ways the driest such period in 1,200 years.
On the Colorado River, Lake Powell and Lake Mead have supported the rapid expansion of population and agriculture in the Southwest. The river supplies about 25 percent of the water used in metropolitan Southern California.
“There haven’t been high enough flows to fill them, by any means, for a long time,” Lund said. “We are asking a lot more out of that river than water is flowing into it.”
This raises the question of whether Western states should be doing more to conserve water for next year and beyond.
“There have been some mandatory water restrictions in some parts of the state, but there is concern from a lot of folks in the water management community that those restrictions should be statewide,” Kearns wrote, referring to California.
Lund said it may be wise to accept smaller shortages this year to help stave off major shortages in the future.
“We are not sure when the drought is going to end,” he said. “You want to make sure you have enough water for next year.”