Sierra's rain-snow zone promises water insight

Scientists' climate research will aid in predictions.

March 20, 2011 

SHAVER LAKE -- In a pounding rain, scientist Matt Meadows skis toward a cluster of snow sensors. The temperature dips, rain turns to sleet, then snow. This is a freezing, soggy, miserable place.

But it's the perfect setting for Meadows and other snowpack researchers. Southeast of Shaver Lake at 6,000 feet in the Sierra, storms switch back and forth between rain and snow -- it's called the rain-snow transition zone.

Scientists say the snowpack and snow melt at these elevations will be the first to change as the climate warms up.

They've laced a one-square-mile area with sensors, logging details about the snowpack, underground water and runoff to help predict changes along the 400-mile Sierra Nevada in the future.

There's a big bonus in this research for California: more accurate spring runoff predictions, which are anxiously awaited each year by the $35 billion farming industry and city officials who deliver water to 20 million residents.

Such precision might not affect delivery allocations that fluctuate each year due to drought and federal protections for dwindling fish. But water managers and state officials would have a clearer idea of how much water will come from the mountain range.

"The research here is very important to everyone," said Meadows, a hydrologist working with a team of researchers checking sensors.

In the project, they're asking these questions: Exactly how much water is in the snowpack in the one-square-mile area? How much water sinks underground, and how much evaporates? How do white fir, ponderosa pine and incense cedar in the forest affect the water?

The traditional approach to snowpack surveying addresses only 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 the snow.

Near Shaver Lake, the so-called Sierra Nevada Critical Zone Observatory takes into account the variations in the landscape, including the slope of the mountain.

"You can see that the snow does not cover the ground uniformly," said hydrologist Peter Hartsough, a postdoctoral scholar from the University of California at Davis, who is helping on the project. "There's almost no snow at the bottom of the trees. It's much deeper when you move into the open areas. There's a great variability."

To guarantee a true picture of the snowpack, researchers must trek through stormy weather and snow-clogged forests to make sure their network of sensors works.

Hartsough last week snowshoed to four sites where snow is measured around trees.

He checked the sensors and confirmed the data by physically measuring the snow at one site.

Then he hiked to the top of a ridge where the wind was howling and rain slanted sideways. Various instruments on the ridgetop track snowfall, temperature, wind speed and chemicals in the rainfall and snowmelt.

A small computer, stashed in a box near a shriveled ponderosa pine, accumulates the information, which Hartsough could have downloaded to a laptop computer for later analysis.

He settled for a quick visual inspection.

"I don't bring the computer up here in this kind of weather," he said. "We come back [with it] at other times of the year."

Throughout the observatory, 57 sensors use sound waves to track the snow's depth. In addition, scientists use satellite images to help them confirm how much snow coverage is actually in the area, says professor Roger Bales, a mountain hydrologist with the University of California at Merced.

Bales, head of the Sierra Nevada Research Institute, leads a team of researchers who installed the clusters of sensors in the Shaver Lake area and the mountains around the American River, above Sacramento.

He said the observatory project could lead to an extensive monitoring of the Sierra, which he estimates would cost about $100 million.

There has been discussion about including some of the funding in a state water bond that would come before voters in 2012. It might take a decade to build the system, Bales said.

"With this kind of information, better decisions would be made about water in the future," he said.

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

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