New technology could provide a much clearer picture for water forecasts
Craig Miller
Frank Gehrke conducts a manual snow survey using a "Mt. Rose gauge," essentially a hollow aluminum tube shoved into the snow at predetermined locations.
In California, where most of our water comes from the mountains, being able to accurately measure the snow pack is vital. And it is in outlier years like this — very dry years, though the same goes for very wet ones — when water managers have the hardest time making accurate predictions.
“Knowing the water content of the snow in an entire watershed is the holy grail for snow scientists,” survey guru Frank Gehrke told me.
During the winter, Gehrke trudges into the woods on a monthly basis to do manual snow surveys for the state Department of Water Resources. DWR uses remote snow sensors, too. But even with all that data we don’t get an exact picture of the snow pack. So scientists from National Center for Atmospheric Research (NCAR) and NASA Jet Propulsion Laboratory (JPL) are developing tools to measure snow with lasers. This new technology has the potential to be that holy grail that Gehrke’s looking for.
Are we in one? Water officials say the answer is “Yes and No”
NOAA
How do you define a "drought?"
As state surveyors trudge into the mountains this week for the season’s second official survey of the Sierra snowpack, the auspices aren’t good. Remote sensors currently show that statewide, water content is averaging just 38% of the average for this date, and less than a quarter of what water managers would hope to see on April first — just two months away.
Consequently, the “D-word” is being nervously bandied about. Are we in a drought?
The state’s newly revamped Current Water Conditions website takes on the question with a definitive “Yes and no.” Drought status, it says “can be very different depending on your location.” Continue reading →
Federal grant enables major new network of Sierra water sensors
Sasha Khokha
A tree at the Fresno County pilot project adorned with sensors
Researchers at UC Merced are set to open a whole new window on the Sierra Nevada. Using two million dollars from the National Science Foundation, hydrologist Roger Bales and his colleagues can now expand on a pilot project to measure the mountains’ “vital signs.”
Bales says beginning next summer, he, UC Berkeley’s Steven Glaser and their team will start installing a network of 20-to-30 instrument clusters throughout the American River watershed, casting a watchful eye over about 2,000 square kilometers that typically gets snow cover. The instruments record factors that affect the mountain’s hydrology, such as temperature, humidity, soil moisture, stream flow and even how much solar radiation penetrates the tree canopy.
Bales says the pilot phase has taught them how to put together a network of wireless sensors that will endure the extreme alpine conditions and still remain reliable (see Sasha Khokha’s post and slide show from March). Continue reading →
A new study finds large losses of springtime snow cover in the West in recent years, raising concerns about water supplies.
Spring snowpack in the West is an essential water resource, particularly in Southwestern states that are prone to summer drought, like California, Nevada, Arizona and New Mexico. (Credit: Wolfgang Staudt on Flickr)
This spring, from the Pacific Northwest and Sierra Nevada, to the Northern Rockies, western mountain ranges were more than just snow-capped – they were buried in the white stuff. In fact, many locations still have more spring snowpack than has been seen in decades.
Head south across the 40th parallel, however, and things are dramatically different. While there is still above average snow throughout the Sierra, a relatively snow-less winter and spring has left much of the Southwest in a drought that has fostered record wildfires. Already local officials are worried there won’t be enough water to get through the summer months ahead. Continue reading →
Governor lifts drought declarations from 2008, 2009
Snow removal near Mt. Lassen. (Photo: KNVN Chico-Redding).
Frank Gehrke summed it up: “Well, it has been a really crazy winter,” said the state’s chief surveyor of the Sierra Nevada snowpack.
Statewide averages from the season’s fourth survey Wednesday, shows water content at 165% of normal for April 1.
The latest survey shows statewide, water content of the Sierra snowpack is 165% of normal. Gehrke says it’s been about 15 years since there’s been this much snow on the ground at this point in the season. Earlier this month, some locations were reporting total seasonal accumulations equivalent to the height of a six-story building. Continue reading →
A wet and wild February provided a huge boost to California’s water outlook
An unusually dry January started some folks thinking that maybe the tap had been shut off for this season. But last month winter came roaring back as Pacific storms brought epic snowfalls to the Sierra. The result: Today’s monthly survey shows the water content of the mountain snowpack at 124% of normal for this date–and even above its normal level for April first.
Check current reservoir levels with our interactive map, below.
Major reservoirs are also above their normal levels for early March. But it still doesn’t mean that contractors on the State Water Project will get all the water they ask for. Officials say they still expect deliveries to come in at about 60% of the volume requested. That’s a number that typically gets adjusted throughout the winter. Continue reading →
The decrease in snowpack would be driven by two processes, according to study author Geoffrey Schladow. With warmer temperatures, more precipitation will fall as rain during the winter, instead of snow. And as any skier knows, when rain falls on snow, it melts the snowpack in what scientists call “rain-on-snow” events.
These findings are a concern since the Sierra Nevada snowpack is often called California’s “frozen reservoir.” That reservoir is critical to the state’s water supply — and it’s free. “What the snowpack affords us is a way to very economically store water,” said Schladow. “If the water is falling as rain, rather than snow, then we have to build more dams and reservoirs to catch it, which is expensive.” Continue reading →
I don’t know Mark Cowin, the director of the state’s Department of Water Resources. I haven’t even met the man, in person. But after listening to and reading his pronouncements about the state’s water supply, I’d guess he’s a guy who would barely crack a smile if he found himself holding a winning lottery ticket. I hazard that opinion because even after today’s great news about the Sierra snowpack–which is a little like finding out the state has won its annual water lottery–what Cowin emphasizes is that California isn’t out of the woods after the dry spell of 2007-2009. But more about that to follow. First, the details on the DWR’s final Sierra snow survey.
DWR announced on Friday that statewide, the water content stored in the Sierra snow is at 143% of normal for the date; 188% in the northern Sierra, 121% in the central mountains, and 139% in the southern reaches of the range. Up and down the Sierra, those figures are more than double the levels of the past two years, and are up to seven times as much as surveyors found in the bone-dry spring of 2007.
Last week, the Department announced it would increase allocations from the State Water Project to 30% of the amount requested from 29 urban and agricultural customers. Today’s snowpack news prompted the department to say that it’s likely to increase deliveries. How much? “Only marginally,” Cowin said in a phone interview this afternoon. “We’ll have to run the numbers, and we’ll probably make that determination in the next week or two.”
How much water will State Water Project customers get, eventually? Let’s run some numbers of our own.
The main reason the department cites for the very tight supply in the midst of a year of “normal” precipitation is the continuing below-average levels at California’s biggest state-owned reservoir, Lake Oroville. As of Friday afternoon, the lake is at 72% of normal for the date and about 60% full. But the stats that Cowin’s water geeks are crunching aren’t about the level today, but where they guess it will be as runoff begins to pour from the snow-blanketed mountains through the Feather River watershed into Lake Oroville. DWR officials have insisted that it believes runoff will be held down because of dry conditions caused by the last three drought years. You wonder if they’ll still believe that after assessing the impact of an unusually wet April and its impact on the snowpack.
While pondering that, here are some other numbers to consider if you want to play what I’ll call the State Water Project Allocation Game:
After running far below its 2008-2009 levels all season, the water storage in Lake Oroville caught up and passed year-ago levels this week. The lake’s storage has increased six percent—more than 150,000 acre-feet—since last Friday.
As noted above, this year’s snowpack is better than double last year’s.
Last year, the state delivered 40 percent of requested water shipments to its SWP customers. The average allocation for the past 10 years is 68 percent.
Considering all of the above—last year’s deliveries, the snowpack, the sudden late-season surge in Lake Oroville’s levels—it’s a no-brainer that water deliveries will at least match last year’s 40 percent. The question is whether the allocation will go higher. All Cowin would say on that subject today is that he thinks that 45%, the amount DWR described two months ago as the upper limit for shipments this season, is still accurate.
But Cowin did say, as he has more and more frequently of late, that a preoccupation with the this year’s water level misses the point about California’s water reality.
“That’s why we’re so concerned when we get the black and white question, ‘Is the drought over,’” he said. “We are in a period of long scarcity in California. We have no idea what next year’s water supply picture will look like. It’s possible we could have two or three more dry years in a row. So we’re trying to get a message out that we need to have a new attitude about how we use water in California, and it shouldn’t depend on this week’s outlook. We need to conserve water just as a way of life.”
If you want to explore the state’s water supply picture for yourself, check out our California Reservoir Watch map, below:
Jeff Dozier approaches an instrument tower on Mammoth Mountain. Photo: Molly Samuel
When Jeff Dozier, a hydrologist at UC Santa Barbara, goes to work, he gets to enjoy quite a view. His snow lab is perched halfway up Mammoth Mountain in the central Sierra. We took a gondola to get up there; the other passengers were skiers and snowboarders itching to get out on the freshly fallen snow.
But the instrument platform from which we enjoyed views of the White Mountains is really only half the story. Dozier’s computer lab has much less of a view. In fact, it has no view. It’s buried under the snow, accessible only through what he calls a “Santa Claus entrance” (in the picture above, you can see the entrance–it’s the white tubular “chimney” extending down into the snow from the center of the platform).
Radiation is an important one. Instruments called radiometers are mounted on the tower. Some point up, measuring the radiation coming from the sun; others point down, measuring how much is reflected back to the sky by the snow.
“Albedo” is the measurement of how reflective the snow is. Something completely white that reflects all of the sun’s energy has an albedo of one; something black, that absorbs all the energy, is zero. Bright, freshly fallen snow has a high albedo, typically above 0.8.
Even if the term is new to you, albedo is probably a familiar concept. As I reported for KQED’s The California Report this morning, Hans Moosmuller of the University of Nevada’s Desert Research Institute explains it in terms of outfits: on a sunny day, if you wear a black sweater you’ll be warmer than if wear a white one. You may notice it with roofs, too. I grew up in Atlanta, in a house with a black roof. Before my parents got an air conditioner, the upstairs bedrooms were unbearable in the summer. If we’d had a white
These radiometers measure radiation coming from the sun. Photo: Molly Samuel
roof, it would have been a little more bearable (though I can’t say it would have helped with Atlanta’s other charming summer attributes, humidity and mosquitoes).
The color sweater you wear has no bearing on the earth’s climate. Roof color could have an effect on a large enough scale. What really matters are the huge swaths of dark and light that cover the globe: ocean and snow.
When warming causes sea ice near the poles to melt faster, areas that had a high albedo (ice is very reflective) become areas with a very low albedo (the blue ocean absorbs more radiation than forests or plain dirt). Moosmuller says it creates a feedback loop. The more dark spots there are, the more radiation is absorbed. So melting speeds up, and warming increases, exposing even more dark areas, and so on.
Pollution plays an important role that’s coming under increasing scrutiny. Deposits of soot or dust make the snow darker, so it melts faster, exposes more dark ground, and there’s that feedback loop again. In the Himalayas soot, also known as black carbon, from stoves, tailpipes, factories, and fires is having a measurable impact.
In the Rockies, there’s a similar problem caused by dust kicked up from ranches. Tom Painter of the University of Utah says the snow in the Colorado River Basin melts a full month earlier than normal. The difference the dust makes is so drastic, Painter says, that “We’re in an entirely new regime for snow melt…it would be like if we started measuring climate impacts fifty years from now.”
No one has yet done a long-term study on the effects of dust and soot on the Sierra Nevada snow pack. Moosmuller says he’s beginning to look into it now. In the summer, black carbon drifts into the mountains from California’s cities, ports, highways and farms in the Central Valley. Tony Van Curen, in a research project at UC Davis, has found that soot blows over from Asia, too.
There is good news in all of this: Black carbon, unlike most greenhouse gases, lingers in the atmosphere only for a couple of weeks. So reducing emissions could have a relatively quick impact.
Despite what might feel like an incessant onslaught of storms these past few months, the word from the Department of Water Resources’s fourth snow survey of the season is… average. Manual and electronic survey readings indicate that statewide, the Sierra snowpack water content is 106% of normal for this date. In the northern Sierra it’s higher, at 126% of normal, while the central and southern Sierra are at 92% and 105%, respectively.
The news was good enough for the DWR to increase its State Water Project allocation from 15% to 20%, but agency director Mark Cowin told reporters on a call Thursday that three years of drought and regulatory restrictions on Delta pumping to protect fish species will keep the allocations far below normal. He said the final allocation, which is announced in May, will likely be between 30% and 40%, depending on April’s precipitation. (Last year’s final allotment was 40%.)
“We’ve had a hit and miss nature to storms this winter, and that has left the State Water Project in not as good a position as we would like to be and perhaps worse than you would expect based upon those fairly good numbers regarding snowpack and precipitation,” said Cowin. “Remember that we started this winter with very poor carry over storage in most of our key reservoirs.”
While many reservoirs across the state, such as Lake Shasta, are at above average capacity for this time of year, others still have a ways to go. The State Water Project’s principal reservoir, Lake Oroville, is currently at 47 percent capacity, which is just 60 percent of normal. Cowin said that the difference between the two lies with where the snow fell this year.
“Clearly we’re going to have water shortages this year,” said Cowin. “We’re all going to have to conserve water. Even if we get to 30 or 40% allocation, those are still low numbers. The ethic of using water efficiently in California has got to be the normal course of business and not dependent on the weather forecast.”
Last month, the U.S. Bureau of Reclamation issued an updated allocation for its Central Valley Project customers that ranged from 25% to 75%.
Check recent levels of California’s major reservoirs on the map, below:
