California drought exposes Sierra's weaknesses

The Fresno BeeFebruary 8, 2014 

High-country blizzards usually bury southern Sierra lake basins in late January, leaving lodgepole pine and red fir trees in snow drifts 15 feet deep.

But snow surveyors making their usual visit this year to Kings Canyon National Park found something most had never seen at 10,300 feet in January. Bare ground.

There are few snow measurements done up this high in the Sierra — a failing that this record-setting drought is exposing. So far, the biggest part of this season's snowpack is up high, which means it is out of reach for conventional snow measurement.

Worse yet, the empty basin at Kings Canyon is more evidence that the drought is stomping all over a wounded mountain range, parched for water after three years of drought.

The Sierra has thousands of square miles of overgrown forests, a potentially catastrophic problem set in motion decades ago by an ill-informed government policy of snuffing all fires.

The unnaturally thick forests are soaking in snow moisture from any new storms now, depriving reservoirs of runoff. Even with some good storms, the stage is set to fill the sky with wildfire smoke this summer.

"If you had a healthier, lower-density forest, you would not be facing the same risks," said Malcolm North, research scientist for the U.S. Forest Service and forest ecology professor at University of California at Davis. "It's a mountain range way out of whack."

Many ecologists say the Sierra is too important to neglect. It is the 400-mile-long guardian of the state's water and air, pouring pure snowmelt into reservoirs each summer and removing carbon dioxide and pollution.

In the best of times, Sierra snowmelt begins at 5,000 or 6,000 feet in spring, slowly moving to higher elevation snow in summer months, providing one-third of the water used by farms, cities and industries.

This year, there's not much of a snowpack below 9,000 feet, and hydrologists are not sure how much snow is above that elevation.

Researchers from NASA and the California Institute of Technology's Jet Propulsion Laboratory last year flew over the high Sierra, experimenting with sophisticated instruments to measure the snow's depth and area. But at the moment, the state does not have a system to adequately measure snow up high, hydrologists say.

It's an issue, particularly in the southern Sierra, the highest part of the range where peaks range above 14,000 feet. The southern Sierra runs from the San Joaquin River south to the Kern River.

With the climate warming and snow levels climbing higher, at least $100 million needs to be invested in more precise snow measurement, said engineering professor Roger Bales of the University of California at Merced.

Bales is director of the university's Sierra Nevada Research Institute, which has been experimenting on better snow measurement for years.

He and his colleagues have laced experimental Sierra plots with sensors to log details about the snowpack. They hope to answer many questions, including: How much water sinks into the ground? How much evaporates? How do trees, shrubs and slopes affect the water?

Conventional measurement right now focuses only on the snowpack. Crews take samples at flat, open meadows across the Sierra. The results are combined with historical records and data from remote sensors called snow pillows, which weigh snow.

"At the moment, the measurements done every year are only getting data in meadows," Bales said. "What about forested areas?"

The Sierra's tree canopy covered 30% to 40% of the forest many decades ago, North said. Now it is 65% to 85%. Researchers are trying to figure out how much water is being lost because of that canopy.

"It's not just a matter of how much moisture is making it to the ground," North said. "How much moisture is getting caught in the canopy and evaporating into the air?"

The fixes for overgrown forests are logging and burning, neither of which alone could accomplish the goal, many experts say.

Both come with political baggage. Logging has been vilified by environmentalists as destroying habitat for sensitive species. Burning has become a target for downwind residents who say their health is compromised by smoke.

Sooner or later, though, destructive fires are bound to happen, North said.

During this drought, there is another immediate concern. The dried, weakened forest also is susceptible to infestation by bark beetles that can turn acres of green into brown. North mentioned the San Bernardino Mountains where drought and beetles devastated a wide swath of trees in the 1990s.

The drought afflicting California now is intense enough to create those situations, North said. The snowpack is a little more than 15% of average for early February.

Is it the worst snowpack on record in California? State chief hydrologist Maury Roos, whose career began in 1957, says he does not remember a year this bad.

"I don't want to jump to conclusions," he said. "There's still 40% of the wet season left, and we're seeing some good signs of a change in the weather pattern. But it is pretty grim at this point."

 

The reporter can be reached at (559) 441-6316, mgrossi@fresnobee.com or @markgrossi on Twitter.

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