By Courtney Swyden
Texas A&M University graduate student Xuesong Zhang is working with his advising professor Raghavan Srinivasan, director of Texas A&M’s Spatial Sciences Laboratory, to evaluate and improve the accuracy and reliability of the SWAT model or Soil and Water Assessment Tool. SWAT, developed by USDA-Agricultural Research Service and Blackland Research and Extension Center in Temple, is a water model used to determine what impacts land management practices have on a watershed.
“The accurate simulation of SWAT can assist the government in making correct decisions about water management practices, which are important for human health, agricultural management, industry development, environmental quality, flood risk assessment and recreation,” said Zhang, a recipient of a $5,000 2004-05 Texas Water Resources Institute research grant.
Zhang, and Srinivasan evaluated the heterogeneity of a watershed through the HRU (Hydrologic Response Unit) concept using the SWAT model. Precipitation, topography, soils, geology and land use, infiltration and evapotranspiration are all highly heterogeneous, or varied, characteristics of a watershed.
Zhang worked to not only improve the accuracy and reliability of SWAT, but also to develop new programs and algorithms to assist the model in describing the hydrologic processes at the HRU scale more realistically.
“In order to facilitate the application of the new algorithms, user friendly interfaces were developed using Visual Basic 6.0 and MatrixVB language,” Zhang said.
The researchers accomplished three major goals. They improved the accuracy of rainfall fields (one of the most important inputs for SWAT) through developing complex geo-statistical algorithm and GIS program and developed a more reliable algorithm using physically based snow routing algorithm to replace the original algorithm. They also developed an advanced automatic parameters calibration program that alleviates the model user from tedious parameters calibration work and provides more objective solutions.
Zhang said he would like to continue to work on the SWAT model, and he hopes to develop a national water quantity and quality system for U.S. EPA’s water management program. Results are expected to be applied in the HUMUS (Hydrologic Unit Model of the United States), CEAP (Conservation Effects Assessment Project) and HAWQS (Hydrologic and Water Quality System), which are supported by EPA.
His research was funded by TWRI through the U.S. Geological Survey as part of the National Institutes for Water Research annual research program. TWRI is the designated institute for water resources research for Texas.
For more information on Zhang’s research, visit “USGS Research Grants”.
