Peering down on California’s water problems

10/08/2010 12:15:48 PM
Don Schrack

A coalition of some of the nation’s best scientific and agricultural minds is designed to give California grower-shippers a boost of irrigation water.

The coalition is looking at the issue from a variety of viewpoints, including from space.

The coalition’s project is funded by the U.S. National Aeronautics and Space Administration, which is teamed with its Ames Research Center, Jet Propulsion Laboratory and the Marshall Space Flight Center.

Other partners include Western Growers, the California Department of Water Resources (DWR), the Agricultural Research Service and Natural Resources Conservation Service of the U.S. Department of Agriculture, plus a handful of California State University researchers, water districts, irrigation consultants and growers.

“Our primary goal is to develop tools for the agricultural community to increase the accessibility and usefulness of satellite data for making irrigation management decisions,” said Forest Melton, a scientist with NASA.

The agency’s satellites regularly fly over California’s crop-producing regions, gathering images and data that can be used for a variety of agricultural applications.

The proposed system is designed to integrate weekly satellite-derived data, Melton said.

“Results to date indicate that weekly observations of crop canopy conditions are adequate to characterize changes in crop coefficients,” Melton said. “However, one of the strengths of this approach is that observations can be obtained from multiple satellites, and we’re evaluating integration of observations from other satellites to increase the frequency at which crop conditions could be mapped.”

The core of the project is determining crop specific evapotranspiration (ET) rates, which is the process by which water evaporates from the soil surface and is transpired by plants.

A program that could provide crop specific ET rates would not solve the state’s water woes, but would be another tool, grower-shippers said.

“It has the potential to be very helpful and to provide more precise information for growers,” said Sonia Salas, science and technology manager for Western Growers. “That’s the beauty of it.”

The California Irrigation Management Information System — CIMIS — already provides regional ET rates, said Kent Frame, senior land and water use scientist and CIMIS program manager for the integrated water management division of DWR. Under development, he said, is computer software that could interpret satellite imagery, insert remotely sensed surface data and then combine ET with a crop coefficient to come up with crop specific information.

A successful result may not be limited to water conservation.

“The end product is hopefully an irrigation tool that will help water use efficiency — and produce better quality produce,” Frame said.

There is the possibility overall water use will not be reduced, he said.

“Growers might actually increase tonnage,” Frame said. “Even utilizing water use efficiency tools could increase water use, but on a per tonnage basis, it would be less.”

If all the pieces of the puzzle come together, the project will be able to project crop specific ET rates on plots of land as small as 100 feet by 100 feet, less than one-quarter of an acre.

“In practice, the information will be most useful for farms of five acres in size or larger,” Melton said.

With the exception of some wine vineyards, nearly all California farms are a minimum of 20 acres.

A limited pilot project is under way this year. A more aggressive project is planned for 2011 and will focus on the San Joaquin Valley.

“We’re currently working with Western Growers, the USDA, and partner-growers to identify specific locations for deployment of wireless sensor networks designed to support evaluation of satellite-based estimates for different crop types,” Melton said. “The crop coefficient and ET maps for the San Joaquin Valley region will be available for all growers to review and evaluate.”

Key to the project’s success will be the participation of some non-coalition members, Salas said.

“If growers actively participate, they can actually see the advantages of the technology,” she said. “Their involvement will be critical.”

Mapping of crop coefficients and estimation of crop ET can be done directly from satellite information in combination with ET estimates from CIMIS, Melton said.

“However, grower participation is critical to evaluating these estimates,” he said.

Where the growers enter the picture is when scientists and the computer program attempt to translate estimates of crop ET into irrigation system run times, Melton said. That requires additional input from growers.

“We also believe that working closely with growers is the best approach for transitioning this work from a successful research effort to a system that provides useful information to growers, and that can assist growers in getting the most value out of the water they have available,” he said.

Grower participation will be as easy at accessing CIMIS online and providing the requested data about crops, soils and irrigation.

Many California growers are already familiar with CIMIS, Salas said.

“Inputting their data will take very little time,” she said. “CIMIS can even be accessed by smart cell phones.”

None of the coalition members is anticipating an immediate decrease in irrigation water use or increased crop yields.

“We’re at the embryonic stage,” Frame said. “We’re just beginning to look into this.”

Nonetheless, there is optimism at Western Growers.

“The idea is efficiency, getting the most you can from every drop of water,” Salas said. “We’ll know much more after we get the results of the pilot projects."



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