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UC Berkeley Press Release

Keck funds project to track life cycle of water

– For most people, it's enough to know that when you turn on the tap, water comes out.

But with the rapid pace of global warming, that may not always be the case.

Diagram of life cycle of water
Aside from periodic measurements of rainfall and stream flow, and images from satellite tracking of storms and snow cover, little is known about the complex life cycle of water. View full-size illustration (Graphic courtesy of NASA)

In an effort to understand the complete life cycle of water and, some day, to predict droughts, floods and water supplies, a team of geologists, biologists and chemists at University of California, Berkeley, is embarking on an ambitious project to track the fate of water through the atmosphere, the trees, the soil, the streams and oceans, and back again into the skies.

"Satellites only show you the clouds. We want to track the invisible water vapor and the water hidden in trees and the soil," said project leader Inez Fung, professor of earth and planetary science and of environmental science, policy and management at UC Berkeley and co-director of the new Berkeley Institute of the Environment.

Fung readily admits that while the data will no doubt help improve current climate models, no one can predict how valuable this information may be until someone collects it. This is why she is grateful to the W. M. Keck Foundation for its new four-year, $1.6 million grant to seed the research.

"This is a very risky project, but an important project," she said. Fung and her colleagues hope to leverage the Keck grant to obtain further funding for their research.

As an example of the complexity of the water cycle, Fung noted that researchers recently discovered that only 30 to 50 percent of the rain that falls on the Amazon comes directly from the ocean. The rest comes from rain that fell earlier in the season and has been recycled through trees and soil and streams back into the atmosphere.

Studies by another project investigator, James Kirchner, professor of earth and planetary science and director of Berkeley's Central Sierra Field Research Stations, have shown that stream flow in the Sierra Nevada fluctuates over a 24-hour period, reflecting the water sucked up by plants in the daytime - even in the dead of winter.

Through a new HydroWatch Center in the Berkeley Institute for the Environment, Fung and her colleagues will take advantage of two "wired" watersheds within the UC Natural Reserve System to set out water monitors that will send researchers real-time data on rain, air moisture, soil water content and stream flow via a wireless network and satellite uplink.

Some of this information, combined with data on temperature, pressure and humidity, will come from wireless sensor motes, originally developed at UC Berkeley's College of Engineering, that will be placed in the tops of trees, embedded in the ground or scattered by the thousands around the water shed. These motes self-assemble into a wireless network that will send data to a central computer in the watershed that then will relay it via satellite to UC Berkeley laboratories. The two California watersheds are along Elder Creek in the Angelo Coast Range Reserve on the South Fork of the Eel River near Branscomb and at Sagehen Creek Field Station, about 20 miles north of Lake Tahoe.

Other information will come from specially designed rain monitors that don't merely measure total rainfall, but collect samples throughout a rainstorm that can be chemically analyzed to determine where water that fell in a particular area originated.

Meanwhile, Kirchner said he plans to place small automated chemical laboratories beside the streams to send back chemical and isotopic measurements "around the clock, around the year." The presence of chloride from sea-salt, for example, indicates the water came from the ocean. A high concentration of carbon, nitrogen or iron indicates the water came from surface soil, while other elements indicate a long residence time in the rock. Water that has evaporated from a plant, on the other hand, has an altered oxygen isotope ratio.

"If we are able to relate the pattern through time as these chemical fingerprints change, we will be able to answer questions like whether stream flow during storms is coming from recent rainfall flowing into the stream quickly, or if it's coming from shallow runoff moving down hillsides and into the channel through the subsurface, or whether the new rainfall is pushing out old water from deep in the fissures between the rocks," Kirchner said.

One goal of the project is to understand how long water resides in shallow soil as opposed to deeper rock, which is important in understanding the spread of pollution and the effectiveness of bioremediation. The team also hopes to uncover the distribution of water vapor in the lowest half-mile of the atmosphere and the distribution of soil moisture, which can help in understanding evaporation rates and, ultimately, the formation of clouds.

All the data will be integrated into a computer model of the life cycle of water, incorporating atmospheric, surface and below-ground variations of water that would serve as a benchmark for broader studies worldwide.

"We have to plan for change in the water supply because of climate change and human actions, such as development," Fung said.

The Keck HydroWatch Center builds on several research centers on campus and is one of the first multi-disciplinary projects of the new Berkeley Institute of the Environment. Besides Fung and Kirchner, the principal members of the HydroWatch Center are Ronald C. Cohen, associate professor of chemistry and director of the UC Berkeley Atmospheric Sciences Center; David Culler, a professor of electrical engineering and computer science now on leave at the Intel Research Network of Labs in Berkeley; William E. Dietrich, professor of earth and planetary science, co-leader of the National Center for Surface Dynamics, and a founder of the National Center for Airborne Laser Mapping; and Donald DePaolo, professor of earth and planetary science and director of the Center for Isotope Geochemistry, a joint facility between UC Berkeley and Lawrence Berkeley National Laboratory.