The first half of 2014 was by far the hottest in California in 120 years of record-keeping, and that heat is exacerbating one of the most devastating droughts in state history.
Month after month, the red and burgundy patches on the California drought map have been spreading, with 82 percent of the state now classified as being in "extreme" or "exceptional" drought on the U.S. Drought Monitor website.
Reservoirs have been shrinking, aquifers have been declining, and an estimated 5 percent of the state's irrigated farmland, from the Central Valley to Southern California, has been left dry and withering.
The increasingly dire water situation across California is being compounded by unusual heat. Long-term weather records maintained by the National Climatic Data Center show that California had its warmest January-June period since record-keeping began in 1895, with the average temperature 4.6 degrees Fahrenheit above average and more than 1 degree warmer than the previous record, set in 1934. July figures have yet to be released.
"In the business of climate science, this is a shattering of a record," said Jonathan Overpeck, a professor of geosciences and co-director of the University of Arizona's Institute of the Environment. "We are fairly certain that the unusual warmth is mostly due to human-caused global warming."
For climate scientists, it can be difficult to trace the influence of climate change in the weather patterns of a year or two. But after decades with average temperatures on the rise, Overpeck said the extraordinary heat during this drought makes it a "global warming drought" that is indicative of the hotter dry spells expected in the future.
While California and the West are naturally prone to drought and have experienced long-lasting mega-droughts in the past, scientists say the long-term trend of rising average temperatures is now packing an extra punch. Hotter temperatures worsen droughts by reducing mountain snowpack and causing more evaporation from streams and reservoirs. Heat also draws more moisture from plants and the soil, and increases the amounts of water needed to irrigate crops and vegetation.
Meteorologist Richard Heim, a drought expert with the National Climatic Data Center in Asheville, North Carolina, said he has been amazed as high temperature records have been blown away this year in California.
"I'm just, 'Wow,' looking at these trends. Can it get any worse? Well, the models say yeah," Heim said. "But how much more can we take as a society, as individual people? And how much more of this can the infrastructure and policies that have been put in place to deal with this at the state level, federal level, local level, how much more of this can you guys take?"
High pressure turns up heat
The main weather feature behind the drought and record temperatures has been a persistent high-pressure ridge over the West and the eastern Pacific Ocean. It has been called the "Ridiculously Resilient Ridge" since Stanford University graduate student Daniel Swain coined that term on his California Weather Blog last year, and the ridge has been keeping storms away from the region.
There is also a two-way relationship between the drought and heat, Heim explained. While the hotter temperatures are contributing to drier conditions, those same dry conditions are in turn amplifying the higher temperatures a bit. This occurs because dry ground tends to heat up faster than wet ground, adding more heat to the air.
In Sacramento as well as Washington, lawmakers have been debating measures that proponents say are aimed at coping with the drought and helping the West become more resilient to face growing water scarcity.
Sen. Barbara Boxer, D-Rancho Mirage, for instance, has recently backed legislation focused on addressing the drought and the impacts of climate change.
"As far back as 1995, climate scientists have predicted that increasing global temperatures would lead to more severe droughts in some regions of the world. We know that climate change is linked to the type of intense, record-breaking droughts that we are experiencing in California," Boxer said by email. "The intensity and frequency of droughts will continue to worsen unless we take steps to address climate change by reducing carbon pollution."
In addition to promoting President Barack Obama's plan to reduce carbon emissions from power plants, Boxer touted the recently-passed Water Resources Reform and Development Act, which she said will help California respond to the deepening drought. The law will enable communities to obtain financing for projects such as water recycling, desalination and repairs of old water infrastructure.
Boxer, who leads the Environment and Public Works Committee, recently introduced another bill that would back local investments in water recycling and groundwater management, expand grants and rebates for water conservation, invest in water-related research, and create an open water data system. She said the measure would "help local communities take steps to become better prepared for drought."
El Nino reprieve unlikely
Earlier this year, predictions of an El Nino raised hopes that a strong warming of the tropical Pacific could lead to drought-ending rains in California and the West. But in the past week, the National Weather Service updated its forecast and said the chance of an El Nino forming has decreased from about 80 percent to 65 percent during the fall and early winter.
State Climatologist Michael Anderson said, however, that an El Nino wouldn't necessarily mean relief because both the wettest year and the driest year in the past 60 years were El Nino years.
"For Northern California, El Nino by itself is not a strong predictor," Anderson said. "So we'll have to look elsewhere."
One wet winter could go a long way toward refilling many of the state's dwindling reservoirs. But the depletion of the state's aquifers is a much deeper problem.
"It will probably take a number of wet years," Anderson said, "to make up some of the groundwater deficits that have been incurred."
In many areas of California and the Southwest, groundwater levels have been declining for years as water has been heavily pumped for farmland and expanding development. The drought has added significantly to those strains.
In a new study, NASA and UC Irvine scientists used satellite data to track changes in the Colorado River Basin and determined that since late 2004, the region has lost nearly 53 million acre-feet of water. That's almost double the volume of water that can be held in Lake Mead, the nation's largest reservoir. The researchers also found that more than three-quarters of the water extracted was groundwater.
"That really forces you to raise your eyebrows and think about how long we can keep doing this, how long we can keep depleting groundwater at that rate," said Jay Famiglietti, senior water scientist at NASA's Jet Propulsion Laboratory and one of the study's authors.
Famiglietti said the era of abundant water is clearly over in the West, and that the rapid declines of many aquifers point to a need for better management and additional studies to determine how much groundwater remains.
"We can see that we're using a lot of it and so now we need to figure out how much is left," Famiglietti said. "We need to do these explorations that need to be done — as if it were oil."
Dramatic declines in the level of Lake Mead offer a glimpse of larger changes in water supplies taking place underground and across the region. The reservoir last month dropped to a record low, driven down by a 14-year drought that scientists say is one of the most severe to hit the Colorado River in more than 1,200 years. The lake, which supplies water to about 25 million people in three states, now stands about 39 percent full.
In the Central Valley, the heart of California's $45 billion agriculture industry, water tables have declined dramatically for years — in some areas so much that the ground has been sinking by nearly 1 foot a year. And in times of drought, farms have been relying more heavily on groundwater to make up for diminished flows of water from the Sierra Nevada and the Sacramento-San Joaquin River Delta.
A recent study by the UC Davis Center for Watershed Sciences estimated that the drought is costing the state $2.2 million this year, including $1.5 billion in direct costs to agriculture. That includes losses of farm revenues as well as higher costs to pump water.
Those costs are likely to gradually climb as the drought persists. And with aquifers declining in many areas, there have been increasing calls for regulation of groundwater.
Unlike nearly all other Western states, California doesn't have a statewide program for managing groundwater. The lack of statewide oversight has meant that owners of private wells can often pump as much as they wish, while some local water districts have permitted their aquifers to decline dramatically.
State lawmakers are now considering groundwater proposals that would strengthen local management procedures while giving the state new authority to step in when necessary as a "backstop" to safeguard water supplies.
Republican and Democratic lawmakers have also been debating proposals for a state water bond to go before voters. An $11.1 billion water bond is on the November ballot, but Gov. Jerry Brown has instead called for a "no-frills" $6 billion plan that would support projects ranging from water recycling to water efficiency improvements. Some of the money would also go to projects to protect and restore water habitats.
As the drought persists, the effects on wildlife are also likely to grow more severe. Already, researchers in some parts of Southern California have been finding that birds of prey such as hawks seem to be reproducing less because they are finding less to eat.
"We've been seeing raptors that have not been breeding successfully, some of them showing signs of starvation, and that's an indicator," said Michael Lynes, director of public policy for the National Audubon Society in California.
The latest Monthly Drought Outlook from the National Weather Service predicts that in the coming weeks, the drought will likely persist or intensify across California and much of the West, with the heat also continuing. That will probably lead to increasing calls from the state and local water districts for Californians to cut back on water use.
The State Water Resources Control Board last month announced mandatory water restrictions, barring the washing of driveways and yard watering that creates runoff, among other things, and calling for fines of up to $500.
The state also instructed local agencies to activate water shortage contingency plans and restrict outdoor watering.