What is in this article?:
- Getting to the root of California‚Äôs water cycle
- Wireless sensor grid
- What winter brings to the Sierra Nevada determines, more than anything, how much water can be tapped in summer by California’s communities and businesses, including the state’s $35 billion agricultural industry.
Wireless sensor grid
Bales already has his eye on a much larger effort. He has proposed creating a wireless sensor grid to monitor the entire snow-covered region of the American River basin — more than 3,000 square kilometers.
“When we can measure these features at the large watershed scale, we can really make a major contribution to the state’s water management,” he says. “Such a grid, along with satellite data, advanced hydrologic models and supporting cyber-infrastructure will form the core of a new water information system for California.”
The Merced-Berkeley collaboration is supported by CITRIS, the Center for Information Technology Research in the Interest of Society, which brings together researchers from different UC campuses to create information technology solutions for social, environmental and health care problems.
CITRIS is one of four California Institutes for Science and Innovation, formed in 2000 and funded both by the state and industry to take on large-scale challenges that demand cross-disciplinary expertise.
“Harnessing wireless sensor technology for watershed-scale monitoring has the kind of research reach that the institutes were designed to address,” says Paul Wright, the CITRIS director.
The growing use of wireless sensor networks has its roots in work first started in 2000 at Berkeley by researchers in the electrical engineering and computer science, and civil and environmental engineering departments.
The Sierra project uses sensors developed by Steven Glaser, professor of civil and environmental engineering at Berkeley and co-principal investigator on the project.
“We had this idea 10 years ago to create a network of sensors, which would communicate with each other, and together make a kind of giant array,” Glaser says. “At that time I was thinking about using it for earthquake monitoring. But Roger’s idea of using a sensor array to help predict water availability from an entire watershed seemed like an exciting opportunity.”
In place of the kind of yardstick approach traditionally used to measure snow depth, an acoustic sensor mounted on a pole a known distance above the rock sends out an acoustic chirp that bounces off the rock surface and returns. This two-way travel time is measured. If winter brings, say, a two-foot snowpack, the surface is now that many feet closer to the sensor, so an acoustic signal will bounce off the snow and return more quickly. Since researchers know the speed of sound through air, they can estimate the distance between the sensor and the snow versus bare rock surfaces. Subtracting the first from the second gives the thickness of the snow.
“This is the same technology used by early auto-focusing cameras,” says Glaser. “You can actually hear the short little clicks of the acoustic signal.”
Branko Kerkez, a graduate student in Glaser’s lab, is the principal researcher on the ground trying to make sure the novel sensor network performs as intended. Born in Bosnia and raised in Florida, he was more familiar with the Berkeley coffeehouse environment than the great outdoors when he started the project.
“I thought I was going to grad school to do math, not so much hiking in the snow,” he says. “At first, it was a clash of worlds. It’s a four- or five-hour drive, and then sometimes another hour snowshoeing. But I’ve grown to like it. It’s very exciting to learn and then directly apply what you learn, and it’s aimed at such an important problem.”
Kerkez hopes to apply what he’s learned to improve large-scale water allocation and to mitigate flooding and produce hydropower.
The former coffeehouse habitué now says, “This is the ultimate project for me.”