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What’s an Albedo? (And Why You Should Care)

Jeff Dozier approaches the instrument tower on Mammoth Mountain.

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).

The snow lab, operated by both UCSB and the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL), uploads information about the snowpack to a website every fifteen minutes. You can see nearly real-time readings on, among other things, snow depth, temperature, humidity, and radiation.

Dozier in the computer lab. Photo: Molly Samuel

Dozier in the computer lab. Photo: Molly Samuel

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

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.

Listen to the radio piece.

Average Sierra Snowpack, More Water Allocated

Gretchen Weber

Photo: Gretchen Weber

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:

View KQED: California Reservoir Watch in a larger map

California Water Update: A Mostly Adequate Year

87760251Almost everywhere you look this week, California is dry. By which we mean the state is experiencing the first truly warm, rainless week since a series of Pacific storms blew through the state in mid-January.

Hydrologists for the state Department of Water Resources and the federal California-Nevada River Forecast Center expect the warm temperatures to trigger the first significant surge of snowmelt for the season. With slightly above-average snowpacks in the Sierra Nevada, that should help continue to raise reservoir levels. Our 2009-2010 rainy season is likely to go down in water history as adequate–short of hopes for a wet year but an improvement on the past three winters, which were much drier than average.

Admittedly, that’s the view from the city, where we get our water out of taps and garden hoses. The picture for agricultural users is not nearly as bright, as we were reminded earlier this week.

On Tuesday, the U.S. Bureau of Reclamation issued an updated allocation for its customers in the Central Valley. The bureau offered a good news-bad news scenario. For CVP customers north of the Sacramento-San Joaquin Delta, the news was mostly good. Agricultural contractors there will get at least 50% of promised deliveries this year; municipal and industrial customers will get 75%. South of the Delta, the news is not so good. Municipal and industrial users will get 75%, but farm customers are guaranteed just a quarter of the water they want.

That 25% zone south of the Delta includes the Westlands Water District and other areas on the west side of the San Joaquin Delta that have suffered severe water shortages, due mostly to the state’s prolonged dry spell and, less directly, to restrictions imposed on Delta pumping to protect Delta smelt and Chinook salmon.

That’s the same area for which Sen. Dianne Feinstein tried to secure extra water this year–even if it meant overriding provisions of the Endangered Species Act. Feinstein’s effort to attach a water amendment to a federal jobs bill failed, but the move apparently prodded the Department of the Interior–the parent agency of the Bureau of Reclamation–to try to find more water for Westlands and its neighbors. This week’s allocation announcement included assurances that the department is still working to secure additional water for west side farmers.

The state Department of Water Resources, which also ships water from the Delta to customers in the San Joaquin Valley and beyond via the California Aqueduct, also issued an updated allocation announcement this week. The department said that for now it’s sticking with its guarantee of 15 percent of requested deliveries this year.

Why such a low figure? The department says it’s because of continuing “poor hydrological conditions” in the Feather River drainage that feeds the State Water Project’s principal reservoir, Lake Oroville. The main symptom of those conditions is the lake’s storage level, now just 57% of average for mid-March. For contrast, look at California’s main federal reservoir, Lake Shasta, less than 100 miles away from Oroville as the crow flies. It’s got 104% of average storage for the date (not to be confused with percent of capacity).

Here’s my amateur, off-the-cuff runoff-watcher’s observation of what’s behind the difference: The Shasta drainage, which captures the upper reaches of the Sacramento, McCloud and Pit rivers as well as lesser streams, has benefited from several storms since mid-January that dumped heavy rains throughout the watershed. Those same storms have dropped lighter amounts of rain further south and east, including over the Feather watershed. The same effect can be seen in the American River basin, which flows into Folsom Lake. A month or so of intense precipitation last year eventually filled the lake; lighter rains this year have led to lower-than-average storage levels in Folsom (84 percent as of this week).

The final word on the water season, of course, will come from the Sierra snowpack and runoff. Stay tuned for the snow melt.

Check recent levels of California’s major reservoirs on the map, below:

View KQED: California Reservoir Watch in a larger map

Latest Snow Survey Offers Hope

Frank Gehrke, left, weighs snow near Echo Summit, to measure water content. Photo: Molly Samuel

Frank Gehrke, left, weighs snow near Echo Summit, to measure water content. Photo: Molly Samuel

His clipboard doesn’t have quite same gravitas as a pair of stone tablets. Nonetheless, Frank Gehrke is sort of the Moses of California water. Once a month he comes down from the mountaintop with a pronouncement on the state of the snowpack in the Sierra Nevada. Today’s message: Whew.

The Department of Water Resources announced today that on average, the water content of California’s Sierra snowpack stands at 107% of “normal” for this date. The figure is derived from a combination of electronic sensors and manual surveys, including Gehrke’s, taken at various points along Highway 50. It’s the first time this season that the statewide average has clocked in above normal.

In the monthly DWR news release, Director Mark Cowin expressed some relief, while warning that the state is still struggling to overcome three abnormally dry winters prior to this one. DWR reports that Lake Oroville, the primary reservoir for the State Water Project, still stands at just 55% of it’s long-term average level for this date. Shasta Lake, however, the biggest reservoir on the federal Central Valley Project, is now above its normal level.

Cowin says the latest readings offer hope that water managers will be able to increase projected allocations to state water customers, currently set at 15% of requested amounts. DWR estimates that final allocations will be “in the range of 35-45%.” Over the past ten years, customers have averaged about two thirds of requested water. Farms often make up for shortfalls by pumping costlier groundwater.

Our interactive map shows the current status of California’s key reservoirs. We also have a short video that takes you into the field with Frank Gehrke, to see how he does his manual surveys.

Storms Offer Big Boost to Sierra Snowpack

For a more expansive analysis of California’s current water picture, and an interactive map of current reservoir conditions, see Dan Brekke’s drought update, posted earlier this week.

State water officials expressed “cautious optimism” after the season’s second survey of the Sierra snowpack.

After a series of Pacific storms dumped several feet of fresh snow on the mountains, today’s (officially the “February”) survey reveals that the snow’s average water content is 115 percent of “normal” for this date (compared to 61% of normal at this time last year).

Water managers say even so, there’s more catching up to do and they still can’t rule out a fourth consecutive year of relatively dry conditions. Nor have they re-evaluated earlier tight allocations planned for agricultural water this year. With a lot of the recent precipitation still locked up in the state’s “frozen reservoir,” Shasta Lake and Lake Oroville are both still hovering around half of their normal levels for this date.

According to today’s release from the Dept. of Water Resources:

“DWR’s early allocation estimate was that the agency would only be able to deliver 5 percent of requested SWP (State Water Project) water this year, reflecting low storage levels, ongoing drought conditions, and environmental restrictions on water deliveries to protect fish species.  The agency will recalculate the allocation after current snow survey results and other conditions are evaluated.”

By the way, if you’ve never had the chance to see how the “manual” component of the monthly snow surveys are done, take about four minutes and watch this video from 2008, when I joined surveyor Frank Gehrke at the Tamarack Flat survey site, off of Highway 50. This is not the site you usually see on the local news. That’s Phillips Station, chosen for media photo ops because it’s right off the highway. Getting to this site takes a little more doing, as you’ll see.

No Surprises in Season’s First Snow Survey

California’s Department of Water Resources (DWR) today released the first of the season’s surveys of snow conditions, an indicator of how much runoff we can expect to fill reservoirs in the spring.

Snow surveyor Frank Gehrke at the Phillips Station survey site. Photo: Gretchen Weber

Snow surveyor Frank Gehrke at the Phillips Station survey site. Photo: Gretchen Weber

At the Phillips Station survey site, just off U.S. Highway 50, lead surveyor Frank Gehrke found about the conditions he expected; water content of the accumulated snowfall there weighed in at 75% of normal. For the five survey sites in the region defined by DWR as the Central Sierra, and for all Sierra survey sites combined, water content was a slightly healthier 85%. While the average represents a slight improvement over last year at this time, when statewide water content clocked in at 76%, DWR officials emphasized that conditions are still below normal. And with the accumulating effects of three prior relatively dry years, some major reservoirs remain at low levels. A sobering example from today’s DWR release:

“Lake Oroville, the principal storage reservoir for the State Water Project (SWP), is at 29 percent of capacity, and 47 percent of average storage for this time of year.”

With several months remaining in the state’s traditional “wet” season, the January survey is perhaps the least reliable indicator of final runoff. According to Gehrke, the season can “go either way from here.”

In a 110-page California Drought Update just released, DWR wrote that:

“Impacts being experienced in the present three-year drought are relatively more severe than those experienced during prior dry conditions – such as the first three years of the 1987-92 drought.”

As such, the agency says it “will move aggressively forward to plan for a potentially dry 2010…”

In February Governor Schwarzenegger declared a drought state of emergency for nine counties that is technically still in effect, though appeals to the federal government for disaster relief have gone unanswered. The Governor has also called on all urban water consumers to cut back their use by 20%.

Early Runoff More than Theory

This post has been modified based on clarifications by the study’s lead author, which are outlined in her comment, below.

A recent study seems to confirm what many have already surmised: The spring melt from the Sierra snowpack is happening sooner.

To get a handle on the timing of mountain runoff, a team led by Iris Stewart of Santa Clara University pulled together data from 52 stream gauges up and down California. For her study, Stewart says she chose only water courses unaffected by dams and diversions, with at least 20 years of continuous data.

Stewart’s data shows that over the 60 years spanning 1948-2008; 80% of the gauges show the “stream pulse” that accompanies peak runoff, coming consistently sooner in the season–an average of about 10 days sooner, though at least one location had shifted up by more than a month. In fact, combining all of the metrics in the study, Stewart says only one gauge showed a later trend.

The trend seems remarkably consistent. Stewart says that despite a warming trend over the past ten years, she has not seen any acceleration of the trend within that period.

Stewart cautions that there’s more work to do on this and was reluctant to draw broad inferences from the study. Runoff in a particular stream is affected by many factors, including the elevation, slope, aspect (which direction it’s facing), vegetation cover and soil composition. Stewart says further study of these variables will better help identify the most vulnerable streams. But the latest results seem consistent with an earlier study in which Stewart found “earlier runoff on a continental scale.”

Scientists are concerned that as average temperatures rise, California’s mountains will see more rain, less snow–and what snow there is will melt off sooner. Reservoirs can only retain so much runoff at once, so if more of the “frozen reservoir” dissipates earlier in the season, farms and cities stand to be caught short of water before the rains return.

Stewart, an assistant professor at SCU’s Environmental Studies Institute, presented her findings this morning to researchers at the Pacific Climate Workshop (known as PACLIM, the conference does not have a website), a semi-annual gathering of climate scientists doing front-line research around North America. The conference in Pacific Grove is organized by the USGS office in Menlo Park.

Over the course of four days, about 60 researchers will hear findings on the climatic implications for fire, fog, glaciers, the ocean and wildlife, among other topics.

Survey Says: Drought Still On

It’s still “cause for concern.” That’s how California’s water chief summed up the water outlook for this summer, based on the latest survey. The Sierra snowpack stands at 81% of normal for this date, according to today’s measurements by the state Department of Water Resources.

Chopping up the Sierra Nevada into segments, Northern California fared a little better at 87%. The situation deteriorates as you move southward, with Southern Sierra stations clocking in at 77% of normal.

In most years, the April survey marks the peak of the season’s snow water content.

Ultimately what matters is runoff, or the total amount of water that actually comes off the mountains with the spring melt. And snowpack isn’t necessarily a good predictor of that, as we heard in David Gorn’s story on The California Report and in his blog notes from today.

Just yesterday the Governor’s Climate Action Team released its 2009 assessment of likely climate change effects in California. One  predicted outcome is that ripple effects from water shortages could run up a tab of $3 billion per year. And that’s the rosy scenario, based on being able to quickly move 5 million acre-feet of water to where it’s needed. Eileen Tutt of Cal-EPA cautions that the actual capacity of the current system to quickly redistribute water is closer to 1 million acre-feet. An acre-foot is about the amount of water that a typical household uses in one year.

Handicapping the Snowpack Derby

shasta_0759

On the eve of the season’s fourth Sierra snow survey, David Gorn files a report that poses the question: “Is it time for Californians to redefine the term “drought?” His report airs on The California Report Thursday morning and some additional thoughts appear here:

Anybody who’s lived in California for a while has been trained to watch the snow. When the monthly snow surveys come around, we handicap them like they’re the Triple Crown. We all know what’s at stake: when it doesn’t snow, our reservoirs don’t get enough runoff, and we dive deeper into drought.

The snowpack gives us a sneak preview of the coming summer, when our other water sources dry up. The last big snow measurement of the season happens on Thursday. State officials are hoping for the best but preparing for something less than a miracle.

We get about a third of our water from snowpack runoff. But the biggest number in water circles is not the number of inches of snow. It’s the amount of runoff that snowmelt produces. And that can be deceiving, which may explain the caution that always seems to pervade official post-survey pronouncements.

Case in point: Last year at this time, the snowpack measurement was 100% of normal and state officials were breathing easier. And yet the amount of runoff that snow produced last year was only 58 percent of normal, and that’s frighteningly low.

What accounts for the difference? Department of Water Resources meteorologist Elissa Lynn says that the wind can disperse snow, which happened last year (maybe Nevada had a “windfall”). Also, a hot spring can melt snow before its time, resulting in too much runoff being released too early, leaving too little for the summer months.

A deceptively full Stafford Lake reservoir in northern Marin County. Photo by David Gorn.

A deceptively full Stafford Lake reservoir in northern Marin County. Photo by David Gorn.

A little rainy weather can be deceiving, too. Even though some local reservoirs around the state topped off–or nearly so–with the late-season storms of February and March, some of the people served by those same reservoirs may still face rationing this summer. That’s because many communities draw their water from multiple sources, which may include mountain runoff.

Projections this year are for snowpack runoff to clock in at about 70% of normal. That beats than the 52% and 58% of the previous two years but is still cause for concern.

Water Allocations Tweaked Slightly Upward

A few drops of good news for farmers and cities this week: a heftier late-spring snowpack means there will be slightly more water headed their way this summer.

Earlier this week, the State Department of Water Resources said it will increase water from state reservoirs from 15% of what cities and farms had hoped for, to 20%.  Today the federal Bureau of Reclamation (Central Valley Project) followed suit and nudged some of its projected allocations up, too.

The five-percentage-point bump is mildly good news for some northern California farmers.  But farmers in the southern San Joaquin Valley are still slated to get zero gallons from federal reservoirs. For that to change would require an April of historically soggy proportions.

The previous nadir for State Water Project deliveries was set in 1991, when urban and industrial customers got 30% of their requested water and farms got zero.