Water vapor - Mississippi River-size amounts of it flowing at hurricane speeds miles above the Earth - is hurtling across the Pacific, an atmospheric river poised to drench a parched Northern California and the Sacramento region as early as Thursday night.

A crack team of science experts is going along for the ride, part of an experiment known as CalWater 2015, many of whom gathered at McClellan Park near Sacramento on Tuesday in preparation for the major weather event and the vital information they hope to pull from the phenomenon.

"It's a real milestone for us. Nothing of this scope has happened," said Marty Ralph, director of the Center for Western Weather and Water Extremes at Scripps Institution of Oceanography in San Diego, of the project he's helping to lead. "One of the drivers of CalWater was the uncertainty of climate projections. We haven't had the data to measure the strength and structure of ARs. ... There's so much potential for the monitoring of atmospheric rivers."

They come from an alphabet soup of agencies, universities and scientific institutes, from NOAA to NASA, USGS and the DOE, to study atmospheric rivers and the role they play in water supply. The researchers will cast a wide net from the Sierra Nevada to the Coast Range and into the Pacific Ocean during a storm system that CalWater forecasters said will produce "copious" amounts of rain into Saturday.

"There will be ample opportunity to store this water, hopefully, and provide a little relief from the drought," said Allen White, a research meteorologist at the National Oceanographic and Atmospheric Administration.

The information the scientists glean, they hope, will help do nothing less than predict the future of water and weather in a California at the mercy of both. Think of atmospheric rivers as a massive water vapor pipeline, responsible for many of the major storms along the West Coast and about half of the rain and snow Northern California sees each year.

Knowing how atmospheric rivers are formed, how strong they are and where they will land can help communities and water experts in California and the West. They can better plan for water storage, storm and disaster preparedness, drought and climate change.

The taps have run dry and the lights have gone out across swathes of Brazil this week as the worst drought in history spreads from São Paulo to Rio de Janeiro and beyond.

More than four million people have been affected by rationing and rolling power cuts as this tropical nation discovers it can no longer rely on once abundant water supplies in a period of rising temperatures and diminishing rainfall.

The political and economic fallout for the world's seventh biggest economy is increasingly apparent. Protesters in dry neighbourhoods have taken to the streets, coffee crops have been hit, businesses have been forced to close and peddle-boat operators have had to cease operations because lakes have dried up.

In São Paulo - the most populous city in South America and the worst hit by the drought - a year of shortages has cut water use in the city by a quarter since last January, but Jerson Kelman, the head of the main water company Sabesp, urged consumers to do more in helping the utility to "prepare for the worst".

"There is a significant part of the population that is not yet aware of the seriousness of the situation and refuses to change habits," he wrote in an op-ed published on Thursday. "They must be convinced to change their behaviour." If the dry spell continues, he warned full-scale rationing would be introduced - something the city government denied would be necessary during last year's elections.

Halfway through the rainy season, the key reservoir for the hemisphere's largest city holds just 6 percent of its capacity, and experts warned Friday that Sao Paulo authorities must take urgent steps to prevent the worst drought in more than 80 years from drying it out.

The system of reservoirs and rivers that provide water to millions in this city have received less rainfall than hoped during the first weeks of the wet season, raising fears they won't be replenished as hoped. Rainfall during the first two weeks of January totaled just 2.9 inches (7.1 centimeters), well below the historic average for the month of 10.7 inches (27.1 centimeters).

The biggest problem is in the Cantareira water system, which is the largest of six reservoirs that provide water to some 6 million of the 20 million people living in the metropolitan area of Sao Paulo city. Cantareira is now down to 6 percent of its capacity of 264 billion gallons (1 trillion liters), the water utility Sabesp said on its website.

Of the remaining five systems, Alto Tiete is at 11 percent of capacity, Rio Claro 25 percent, Alto Cotia 30 percent, Guarapiranga 40 percent and Rio Grande 70 percent.

The last three years of drought were the most severe that California has experienced in at least 1,200 years, according to a new scientific study published Thursday.

The study provides the state with breathtaking new historical context for its low reservoirs and sinking water tables, even as California celebrated its first good soaking of the season.

Analyzing tree rings that date back to 800 A.D. -- a time when Vikings were marauding Europe and the Chinese were inventing gunpowder -- there is no three-year period when California's rainfall has been as low and its temperatures as hot as they have been from 2012 to 2014, the researchers found.

Kevin Anchukaitis collects an tree-ring sample from a 300-year old blue oak in California. 2014 image by Daniel Griffin.

"We were really surprised. We didn't expect this," said one of the study's authors, Daniel Griffin, an assistant professor in the University of Minnesota's department of geography, environment and society.

The report, published in the journal of the American Geophysical Union, was written by researchers at Massachusetts' Woods Hole Oceanographic Institution and the University of Minnesota.

The scientists measured tree rings from 278 blue oaks in central and southern California. Tree rings show the age of trees, and their width shows how wet each year was because trees grow more during wet years.

The researchers compared the information to a database of other tree ring records from longer-living trees like giant sequoias and bristlecone pines, dating back 1,200 years.

Meanwhile, the rain that California received this week provided a promising start to a winter that water managers say needs to be relentless and drenching to break the drought cycle.

Most of the US Southwest region has been suffering from a persistent lack of rain and snow. More than 64 million people are directly affected by drought in the Southwest and Southern Plains, and far more are indirectly affected, mostly in agricultural sector.
California is experiencing the worst drought conditions. The past three years have been the driest in California history, and it looks like 2014 will be the hottest on record. Since April 2014, the entire state of California was in some stage of drought. 80 % was in extreme drought and 55 % was classified with exceptional drought in middle of November 2014. In period between October 1, 2013 to September 30, 2014, California received just 20 % of normal rainfall and 18 % of it snowpack. Reservoirs in the state collectively stood at 57 % of its capacity.

The annual fall migration of Chinook salmon has been delayed by warmer water temperatures and slow-flowing streams in parts of California as the state's three-year drought drags on, hatchery officials said Monday.

Cool November temperatures usually bring thousands of adult salmon from the Pacific Ocean into streams and rivers to spawn. But this year, fish have been slow to migrate up the American River to the state's hatchery near Sacramento, said William Cox, manager of the fish production and distribution program at the California Department of Fish and Wildlife.

"They haven't come into the river at the same time that they would normally," Cox said.

Wildlife researchers check the strength of the fall salmon run by going out to creeks and rivers and counting them. This year in the American River and its tributaries, the survey crews found just 210 corpses of salmon that had presumably spawned and died in the streams, a tenth of the number normally encountered, Cox said.

At another hatchery, near the Central Valley city of Merced, a higher than normal number of male salmon are arriving unable to provide viable sperm to spawn, he said.

State wildlife experts are not entirely sure why the salmon are late, but some speculate that warmer temperatures and slower flow in the American River might be to blame.

"Folsom reservoir is low and warm right now, so the water coming down isn't as cold as the fish prefer," said Kevin Thomas, a supervising environmental scientist with the state.

The city of Los Angeles has a unique way to beat the state's historic drought, and the concept revolves around recycling.

The city is giving away free rain barrels to 1,000 residents. The goal is to collect rain water to be used on lawns and gardens. The offer is limited to residents of Los Angeles.

The 55-gallon barrels are re-purposed syrup containers from Coca-Cola Co., which is partnering with the city for this campaign.

There are three opportunities to pick up a free barrel:

• Saturday, Nov. 15, 9 a.m. - 1 p.m. -- Los Angeles Valley College, Valley Glen
• Saturday, Nov. 22, 9 a.m. - 1 p.m. -- Los Angeles Harbor College, Wilmington
• Saturday, Dec. 6, 9 a.m. - 1 p.m. -- Los Angeles City College, East Hollywood

To learn more about this program, visit www.bpw.lacity.org.

NASA's Jet Propulsion Laboratory has sounded a stark warning over California's sustained drought, publishing its latest findings where satellite surveys show a rapidly depleting groundwater supply.

And with California as the United States' most valuable agricultural state, and thus key to America's food supply (and much of the world's as well) that could mean drastic consequences for food commodity prices and potential shortages.

The Nature Climate Change journal carried the report, which Think Progress summarized:

A new Nature Climate Change piece, "The global groundwater crisis," by James Famiglietti, a leading hydrologist at the NASA Jet Propulsion Laboratory, warns that "most of the major aquifers in the world's arid and semi-arid zones, that is, in the dry parts of the world that rely most heavily on groundwater, are experiencing rapid rates of groundwater depletion."

The groundwater at some of the world's largest aquifers - in the U.S. High Plains, California's Central Valley, China, India, and elsewhere - is being pumped out "at far greater rates than it can be naturally replenished."

The most worrisome fact: "nearly all of these underlie the word's great agricultural regions and are primarily responsible for their high productivity."

Amid California's record drought, towns up and down the state are rolling out smartphone apps that enable people to snap pictures of neighbors and businesses who are violating water restriction rules and "play water cop":

The apps put more boots on the ground to spot waste and leaks that might go unnoticed, officials say. They say the high-tech citizen reporting programs are intended to encourage water conservation, and not to be used as evidence to fine offenders.

But at least one private company is taking things a step further. Creators of Vizsafe, a neighborhood watch app, have added a feature allowing users to map photos of water wasters - a practice dubbed "drought shaming" on Twitter and Instagram.

Here are a few examples:

© Unknown

A poor, rural community in Calfornia's agricultural belt has run out of water.

At least one California town has gone dry, and many are expected to follow soon. East Porterville, in Tulare County is now without water, as the wells that feed it have dried up. Residents, according to Yahoo! News, now have to drive to the local fire station to get water to drink, bathe, and flush the toilet. And ironically, the town is near what was once the largest freshwater lake in California.

Tulare County, which relies heavily on the agricultural industry, is parched. The some 500 wells that feed its residents and farmers have gone dry. And the county says that it may be years and cost $20 million before a new groundwater management program, which includes a hookup between East Porterville and Porterville's water systems, goes into effect.

The county is named for Tulare Lake, which was once the largest freshwater lake west of the Great Lakes. It was drained for regional agricultural purposes, begining in the early 20th Century. The lake basin is now some of the most fertile soil in the Central Valley, the most productive agricultural region of the United States. Although dry for the most part, the lake occasionally reappears after unusually high levels of rainfall or snow melt, the last time being 1997.

Earlier this month, a 5,000-gallon-water tank, donated by the county's Sheriff's Association was delivered to East Porterville, and that is primary source of water for this low-income community. Residents now drive to the fire department with empty water jugs and pump water from the tanks to take home. The county has also been supplying free bottled water, paid for by the state, to residents for drinking and cooking.

However, there are worries within the community that the county might use the bottled-water handout to identify undocumented residents or condemn homes that are in disrepair. Non-profit groups and churches have also been trying to help supply water to East Porterville residents.

"It's a disaster," says Andrew Lockman, manager of the Tulare County Office of Emergency Services. "It's not a tornado, it's not a hurricane, it's a quiet disaster."