Posts Tagged California drought

Mar 24 2015

No, California won’t run out of water in a year


Lawmakers are proposing emergency legislation, state officials are clamping down on watering lawns and, as California enters a fourth year of drought, some are worried that the state could run out of water.

State water managers and other experts said Thursday that California is in no danger of running out of water in the next two years, even after an extremely dry January and paltry snowpack. Reservoirs will be replenished by additional snow and rainfall between now and the next rainy season, they said. The state can also draw from other sources, including groundwater supplies, while imposing tougher conservation measures.

“We have been in multiyear droughts and extended dry periods a number of times in the past, and we will be in the future,” said Ted Thomas, a spokesman for the California Department of Water Resources. “In periods like this there will be shortages, of course, but the state as a whole is not going to run dry in a year or two years.”

The headline of a recent Times op-ed article offered a blunt assessment of the situation: “California has about one year of water left. Will you ration now?”

Jay Famiglietti, senior water scientist at NASA’s Jet Propulsion Laboratory and a professor at UC Irvine, wrote about the state’s dwindling water resources in a March 12 column, citing satellite data that have shown sharp declines since 2011 in the total amount of water in snow, rivers, reservoirs, soil and groundwater in California.

In an interview Thursday, Famiglietti said he never claimed that California has only a year of total water supply left.

He explained that the state’s reservoirs have only about a one-year supply of water remaining. Reservoirs provide only a portion of the water used in California and are designed to store only a few years’ supply. But the online headline generated great interest. Famiglietti said it gave some the false impression that California is at risk of exhausting its water supplies.

The satellite data he cited, which measure a wide variety of water resources, show “we are way worse off this year than last year,” he said. “But we’re not going to run out of water in 2016,” because decades worth of groundwater remain.

Still, the state’s abysmal snowpack and below-average reservoir levels could exacerbate the overpumping of already depleted groundwater reserves — a problem detailed in an in-depth Los Angeles Times article Wednesday.

There’s little debate that the state’s water situation is troubling, but there is some improvement from last year. Water levels in some of the state’s largest reservoirs in Northern California are higher than last year at this time, largely because of big December storms. But some smaller Southern California reservoirs aren’t doing so well and have lower reserves than a year ago.

The Department of Water Resources did not have a readily available estimate of the total water supply in California or the amount expected to be used over the next year.

Just because California is not exhausting its water supply “doesn’t mean we’re not in a crisis,” said Leon Szeptycki, executive director of the Water in the West program at Stanford University, who called the state’s snowpack, at 12% of average, “both bad for this year but also a troubling sign for the future.”

State officials said stricter conservation measures, including watering restrictions for cities and big cuts in water deliveries to San Joaquin Valley farmers, will help reduce the drain on reservoirs.

Madelyn Glickfeld, director of the UCLA Water Resources Group at the Institute of the Environment and Sustainability, said the drought is so serious that stricter conservation measures are urgently needed. “But I’m confident California’s government will not let this get to the point where water is not coming out of peoples’ faucets.”

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Mar 3 2015

California drought likely a fixture, says Stanford study

Two piers lay on the shoreline at Shadow Cliffs Regional Recreation Area in Pleasanton, Calif., on Friday, Jan. 9, 2015. The man-made lake’s water level remains at historically low levels, about 10 feet below normal for the winter season. (Doug Duran)

Human-caused climate change is increasing drought risk in California — boosting the odds that our current crisis will become a fixture of the future, according to a major report Stanford scientists released Monday.

The finding comes as cities across the Bay Area wrap up the warmest three-month stretch of winter on record.

The new study looked at data from the past and simulations foretelling the future to understand the influence of greenhouse gases on California.

“What has happened in California has been a clear warming trend over the historical record … that probably would not have happened without humans,” said Stanford climate scientist Noah Diffenbaugh.

The continuation of global warming “will result in more frequent occurrences of high temperatures and low precipitation that will lead to increased severe drought conditions,” said Diffenbaugh. The research was published in the March 2 issue of the journal Proceedings of the National Academy of Sciences.

Low precipitation, alone, doesn’t cause a drought — what matters is whether it happens in a warm year, according to members of the Stanford team. They don’t offer specific recommendations but say their findings could help California plan for the future.

The news comes on the eve of this winter’s third manual snow survey, taken atop the Sierra on Highway 50. Other readings reveal that statewide, the snowpack water content is just 19 percent of the historical average for the date.

Reinforcing the drought’s threat, one weather agency is reporting that many Bay Area cities have broken records for the warmest winter in history. Average temperatures for December through February were 54.44 degrees in San Jose, up from the 54.42 degree record of 1996; 52.62 degrees in Livermore, up from the 51.72 degree record of 1996; and 57 degrees in San Francisco, up from the 55.70 degree record of 1970, according to Jan Null of Golden Gate Weather Services.

The Stanford study supports the growing recognition that warming temperatures can worsen a drought that is driven by declining precipitation, noted Richard Seager of Columbia University’s Lamont-Doherty Earth Observatory, who was not involved in the research.

“This is happening all over the world — there is nothing unusual in terms of California,” said Seager.

The Stanford team previously reported that the conditions behind our current drought — a high pressure system parked over the Pacific Ocean, diverting storms away from California — are much more likely to occur amid concentrations of greenhouse gases.

The new study goes further. Using a recently released trove of 120 years of historical data, the researchers found more than a doubling of the frequency of drought years. There were six droughts in past 20 years (1995-2014), compared to 14 in the previous 98 years (1896-1994.)

What’s happening? Imagine flipping two coins, one for precipitation and one for temperature, said Diffenbaugh, associate professor of Environmental Earth System Science at Stanford.

Until recently, precipitation and temperature occurred independently.

But climate change means that the temperature coin is landing on warm weather most of the time. So even as precipitation varies, the combination of both warm and dry is more common. We see little rain, snow melts earlier, and soil and plants lose more water.

“Low precipitation isn’t enough to create a drought. The key difference is temperature,” said Diffenbaugh. And that’s what is changing.

Seager agrees that climate change will produce warmer weather, although he contends that our recent extreme heat is due to natural variations in sea surface temperatures, “far in excess of what you would expect from background greenhouse gases,” based on his National Oceanic and Atmospheric Administration-sponsored research.

He agrees that California “will also face tremendous water problems as the climate changes, because of warmer temperatures, less snow, shorter and sharper winters, and warming that takes moisture out of the soil.”

The Stanford team doesn’t have data for the future, of course, and it’s impossible to run a real-world experiment. So they created climate simulations to peer into the future.

Their models show that the warming trend is likely to continue, boosting the odds that a heads-tails coin toss — co-occurring warm and dry years, creating drought — will climb in the coming decades.

Droughts have occurred throughout California’s pre-human history, just as the coin toss example would predict, they say. And nature creates its own variability, with volcanic eruptions and solar fluctuations.

But steadily rising temperatures — caused by burning fossil fuels and clearing forests — increases the probability of such conditions, they found.

“Continued global warming will result in more frequent occurrences of high temperatures and low precipitation,” said Diffenbaugh, “leading to more of the severe drought conditions that we’ve been experiencing.”

Read the original post: | By Lisa M. Krieger

Jan 22 2015

California drought could end with storms known as atmospheric rivers

California’s drought crept in slowly, but it could end with a torrent of winter storms that stream across the Pacific, dumping much of the year’s rain and snow in a few fast-moving and potentially catastrophic downpours.

Powerful storms known as atmospheric rivers, ribbons of water vapor that extend for thousands of miles, pulling moisture from the tropics and delivering it to the West Coast, have broken 40% of California droughts since 1950, recent research shows.


“These atmospheric rivers — their absence or their presence — really determine whether California is in drought or not and whether floods are going to occur,” said F. Martin Ralph, a research meteorologist who directs the Center for Western Weather and Water Extremes at the Scripps Institution of Oceanography at UC San Diego.

The storms, which flow like massive rivers in the sky, can carry 15 times as much water as the Mississippi and deliver up to half of the state’s annual precipitation between December and February, scientists say. Though atmospheric rivers are unlikely to end California’s drought this year, if they bring enough rain to erase the state’s huge precipitation deficit, they could wreak havoc by unleashing floods and landslides.

Scientists using a new type of satellite data discovered atmospheric rivers in the 1990s, and studies since then have revealed the phenomenon’s strong influence on California’s water supply and extreme weather.

This month, a group of government and university scientists, including Ralph, are launching a major field experiment to better understand atmospheric rivers as they develop over the Pacific. Through the end of February, some researchers will fly airplanes above storms as they pass through, while others will monitor them from ships hundreds of miles off California. As the storms make landfall, the scientists will collect data with ground-based instruments.

“We’re going to measure the heck out of them,” Ralph said.

Scientists will use the information to try to improve atmospheric river forecasts, including where they will hit hardest and for how long. That could help communities prepare for flooding and allow water managers to make better use of storm runoff.

These atmospheric rivers — their absence or their presence — really determine whether California is in drought or not and whether floods are going to occur.- F. Martin Ralph, a research meteorologist who directs the Center for Western Weather and Water Extremes at the Scripps Institution of Oceanography at UC San Diego.

California usually needs about five good atmospheric rivers each winter to fill reservoirs, stimulate spring vegetation growth and build snowpack to healthy levels, said Michael Anderson, a climatologist for the California Department of Water Resources. But how much the storms boost the state’s water supply depends on the characteristics of each one, including how cold it is, whether it makes landfall toward the north or south, and whether the precipitation falls mostly as rain near the coast or as snow in the mountains.

Jay Jasperse, chief engineer for the Sonoma County Water Agency, calls atmospheric rivers “our water supply up in the air.” The agency, which operates two reservoirs in the Russian River Valley, one of the state’s most flood-prone watersheds, has been seeking more precise forecasts to make better decisions about releasing water from reservoirs to accommodate storm runoff or conserving it to use as drinking water.

“We want to better handle these short, intense rainfall events,” Jasperse said.

If atmospheric rivers fail to arrive, California could be in serious trouble. That’s what happened last winter, when a ridge of high pressure lingered off the West Coast for months, blocking storms and intensifying the drought.

An atmospheric river broke through last February but didn’t bring enough rain to make a big improvement. In December, a strong atmospheric river drenched Northern California, but much of it fell as rain near the coast rather than snow in the mountains. That means the state will need several more big storms by the end of next month to build up its snowpack, which in the Sierra Nevada remains at less than half of normal.

As much as Californians might hope for a series of atmospheric rivers to sweep in and end the three-year drought, experts warn that so much rain at once could bring devastation.

California’s most severe storm event on record was caused by a series of atmospheric rivers that began in December 1861 and poured rain for weeks. The storms caused such extensive flooding in the Central Valley that the state Capitol was temporarily moved from Sacramento to San Francisco.

Ten years ago, an atmospheric river brought record-setting rain to Southern California, causing a mudslide that killed 10 people in the Ventura County beach town of La Conchita.

Atmospheric rivers are expected to grow stronger over the century as global warming increases the amount of water vapor that can be lifted out of tropical oceans and pushed to higher latitudes.

A 2011 simulation by the U.S. Geological Survey found that a hypothetical megastorm — an atmospheric river event so strong it happens only once every 100 to 200 years — could be more catastrophic than a major earthquake, over several weeks bringing 10 feet of rain and hurricane-force winds, widespread flooding, landslides and $300 billion in property damage.

Dale Cox, a USGS project manager who oversaw the disaster scenario, said atmospheric rivers “provide us water, but they are also a major source of our calamity.”

“Everybody’s hoping for them,” he said, “but we don’t want too many.”


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