California Still Needs 11 Trillion Gallons Of Water To End Its Drought

First published on ClimateProgress.org, a project of the Center for American Progress Action Fund, which was recently named one of Time magazine’s Top 25 blogs of 2010.

December has been a wet month for California, as the “Pineapple Express,” a tropical atmospheric river of moisture barreling off the Pacific Ocean, brought inches of rain and punishing winds to West Coast residents. Downpours caused flash flood warnings, freeway closures, mudslides, and record monthly precipitation totals — achieved in one day.

Even after such spectacular rain and snowfall — rare for drought-stricken California — it is going to take a lot more than that to get the state anywhere close to normal water levels. On Thursday, the U.S. Drought Monitor said that “two consecutive weeks of widespread heavy (7-day totals of 4 to 12 inches) precipitation, augmented by above-normal autumn precipitation,” not only flooded parts of California, but also provided it with “a foothold for drought recovery.”

However, “3 straight winters of subnormal precipitation will take time (possibly several consecutive wet winters) to fully recharge the reservoir levels and subsoil moisture back to normal.”

The latest drought map shows how much progress California still needs to make to get out of its deep, three-year-long drought. One-hundred percent of the state is categorized as “abnormally dry,” with 98.4 percent in moderate drought or worse. Even with two weeks that saw inches of rain break local and daily records, more than 77 percent of the state is in “extreme drought.”

“With several more months still left in the wet season, it is possible that additional storms similar to the ones that just occurred will continue to chip away at the long-term hydrological drought, and the addition of lower temperatures would help build the snow pack,” the drought summary concluded. “‘Cautious optimism, but still a long way to go’ would be the very short summary for this week’s California drought picture.”

So how many gallons is that “long way to go” as the state hopes to fight back from the most severe drought of the last 1200 years?

Last week, a team of scientists led by Jay Famiglietti of NASA’s Jet Propulsion Laboratory used satellite data to calculate for the first time ever that California would need 11 trillion gallons of water to recover from the punishing three-year drought.

“Spaceborne and airborne measurements of Earth’s changing shape, surface height and gravity field now allow us to measure and analyze key features of droughts better than ever before, including determining precisely when they begin and end and what their magnitude is at any moment in time,” Famiglietti said. “That’s an incredible advance and something that would be impossible using only ground-based observations.”

Every year since the start of the drought in 2011, four trillion gallons have disappeared from the Sacramento and San Joaquin river basins, mostly due to agricultural tapping of groundwater supplies as reservoirs ran low. This is more than California’s residents consume annually for domestic and municipal purposes. Filling that 11 trillion gallon hole would take another three years.

The airborne data also revealed that previous estimates of Sierra Nevada snowpack were twice as high as they actually were. The recent Pineapple Express storms have pushed Sierra precipitation levels to 142 percent above normal. Yet the extended heat and drought, as well as the fact that too much of the recent precipitation has been rain rather than snow, has kept snowpack levels at 48 percent of what they should be.

The next three months look to remain wetter than they have been in previous dry winters, according to a recent NOAA report. The hope is that temperatures will not be so high that too much of the precipitation in the mountains falls as rain, which does not add to the snowpack. The rest of the state relies heavily on the stored water in that snow throughout the rest of the year to keep reservoirs from dropping too precipitously.

We can’t say that the drought in California was caused by climate change, but there is a great deal of research concluding that the record high temperatures recently plaguing the state have made the drought a lot worse than it would have been otherwise. “For the California drought, this evidence includes the fingerprints of higher temperatures and changes in atmospheric circulation patterns in a climate pumped up by greenhouse gases emitted by human activities,” said Peter Gleick, the president of the Pacific Institute, in a Sacramento Bee op-ed. “These higher temperatures have led to extra drying of soils, greater agricultural water demand, earlier and faster snowmelt, and higher evaporative losses in reservoirs.”

California businesses are paying attention. According to a report by CDP, 86 percent of the companies in the state surveyed said they factored climate change into their business plans.

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