Thirty years of data from
many U.S. watersheds went
into constructing the computer
model called SWAT, used to
predict the effects of farming
practices on water quality.
Water samples are still being
collected weekly to validate
the model. Here, technician
Jeff Nichols collects a sample
from the Walnut Creek watershed
in Ames, Iowa, for analysis.
When SWAT talks, the State of Texas listens. In fact, much of the world
SWAT is a computer model that tells where in a watershed a water pollution
problem is coming from and what to do about it. SWAT stands for Soil
and Water Assessment Tool, a name that belies its practical use to farmers,
ranchers, water quality managers, and legislators. The model points
to solutions, which in turn leads to adoption of conservation practices
around the world.
In Texas alone, where SWAT was developed by a team of ARS
researchers, many people who have never heard of a computer model are
benefiting from it. People in the Fort Worth metropolitan area, for
example, will have a longer lasting and less costly water supply because
of reduced sedimentation in reservoirs. Lake Aquilla, a drinking-water
reservoir in central Texas, will not die prematurely. And in parts of
west Texas, the drought's effects have been eased a bit.
In most of these cases, Texas legislators, water districts, and river
authorities were impressed enough by SWAT numbers to pay part of the
costs for farmers in these areas to apply conservation measures that
SWAT showed would work. These included terracing and other erosion-control
measures to hold soil in place and slow its journey into reservoirs;
better nutrient management on agricultural land and on confined animal-feeding
operations to prevent algal blooms that impart off-flavors to water;
and removal of juniper and mesquite brush to increase stream flow in
drought-stricken areas of Texas.
All these examples came about because an ARS teamagricultural
engineers Jeffrey G. Arnold and Kevin W. King and agronomist James R.
Kiniry, all with the Grassland Soil and Water Research Laboratory in
Temple, Texasdeveloped SWAT and handed it over to scientists and
engineers with USDA's Natural Resources Conservation Service (NRCS)
and the Texas Agricultural Experiment Station (TAES). They use the model
to analyze watersheds.
Examples of success multiply with each userand this ARS team
has shared the model with thousands of users all over the world.
The team used 30 years of ARS research data to construct the model
and then worked closely with people from TAES and NRCS to make sure
their product would be useful.
"It had to result in cleaner water, longer lived reservoirs, and
healthier farms and landscapes, or it would have been nothing more than
an academic exercise," Arnold says. He can visit many watersheds
in central and west Texas alone and see the tangible benefits of the
model's calculations.By Don
Comis, 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.uda.gov.
Jeffrey G. Arnold, Kevin
W. King, and James R. Kiniry
are with the USDA-ARS Grassland
Soil and Water Research Laboratory, 808 E. Blackland Rd., Temple,
TX 76502; phone (254) 770-6500, fax (254) 770-6561.