Researchers, engineers, extension
specialists, and students worldwide can now better understand how water and
chemicals move through soil, thanks to one of ARS' most successful cooperative research
and development agreements (CRADAs).
This CRADAbetween the George E. Brown, Jr., Salinity Laboratory (of
ARS) in Riverside, California, and the Colorado School of Mines' International
Ground Water Modeling Center (IGWMC) in Goldenallows for distribution and
continuous improvement of a state-of-the-art computer model named HYDRUS.
ARS scientists and collaborators developed the model at the laboratory over
the last two decades. The model allows users to simulate, in one or two
dimensions, water moving from the soil surface to and into groundwater. They
can also use it to visualize how chemicals such as pesticides would be
transported in different soils.
ARS soil scientist Rien van Genuchten and University of California civil
engineer Jirka Simunek are lead authors of the computer program. IGWMC
distributes the model, provides hands-on help to users, runs short courses on
its use, and gives feedback to ARS so the researchers can improve it.
So far, IGWMC has sold more than 500 copies. Four substantial revisions to
the programas well as dozens of minor improvementshave resulted
from user feedback.
HYDRUS allows agricultural engineers to design irrigation and drainage
systems that provide optimal water to crops, while minimizing the transport of
fertilizers and pesticides to groundwater.
"Rather than doing costly field experiments by trial and error,
researchers can use HYDRUS first to find out which scenarios work best,"
says van Genuchten. Once the program calculates the most realistic situations,
a limited number of field experiments can be run to test the results. Too, he
says, scientists could use the model to improve the analysis of experiments
that have already been carried out and then extrapolate their findings to other
locations, crops, or irrigation methods.
HYDRUS provides an easy-to-use, Windows-based format. While most groundwater
models display results as columns of numbers that can be difficult to interpret
and manipulate, HYDRUS displays results visually with graphs or contour lines.
It can even use animation to illustrate how a fertilizer, for example, would
move through the soil.
"The program makes it very easy to model complex systems," says
John Selker, an associate professor of bioresource engineering at Oregon State
University in Corvallis. Farmers, consultants, and students use it to visualize
how different flow processes work in the soil. "It's really quite a
remarkable achievement," he says.
HYDRUS has also found widespread nonagricultural use. For example,
researchers at former nuclear testing facilities in Nevada are using the model
to make sure their landfill covers work adequately. These soil covers prevent
rainfall and runoff from leaching through the landfill and carrying low-level
radionuclides to groundwater.
"We're very pleased that many groups outside of agriculture are using
HYDRUS," says van Genuchten.
For a demonstration version of the model, contact van Genuchten or visit
http://www.mines.edu/research/igwmc/zipfiles/
on the World Wide Web.By Kathryn Barry Stelljes,
Agricultural Research Service Information Staff.
This research is part of Water Quality and Management, an ARS National
Program (#201) described on the World Wide Web at
http://www.nps.ars.usda.gov/programs/nrsas.htm.
Rien van Genuchten is in the
USDA-ARS Soil Physics and Pesticide Research Unit,
George E. Brown, Jr.,
Salinity Laboratory, 450 W. Big Springs Rd., Riverside, CA 92507-4617;
phone (909) 369-4847, fax (909) 342-4964.
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