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United States Department of Agriculture

Agricultural Research Service

Title: Use of Data from An Intensively-Monitored Field Site to Determine Input Parameters for Swat

Authors
item Feyereisen, Gary
item Strickland, Timothy
item Bosch, David
item Truman, Clinton
item Potter, Thomas
item Sullivan, Dana
item Wauchope, R - 6602-05-00 RETIRED
item Hubbard, Robert

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: June 7, 2006
Publication Date: July 12, 2006
Citation: Feyereisen, G.W., Strickland, T.C., Bosch, D.D., Truman, C.C., Potter, T.L., Sullivan, D.G., Wauchope, R.D., Hubbard, R.K. 2006. Use of data from an intensively-monitored field site to determine input parameters for swat. In: Proceedings of the American Society of Agricultural and Biological Engineers International Meeting (ASABE). Portland, OR, USA. Paper No. 062257.

Interpretive Summary: Since the mid 1990’s, a cotton-peanut crop rotation has dominated the agricultural landscape in South Georgia. In support of this cropping system, field research is going on near Tifton, Georgia to study water conservation, soil organic matter levels, and impacts of chemicals an groundwater and stream water quality. The field study has been developed to quantify differences between conventional “bare soil” tillage and conservation strip tillage methods. Once the differences between the treatments are quantified at the field level, there is a need to estimate the impact of the differences over larger areas of land. The estimation can be accomplished by using computer simulation models that estimate the hydrologic cycle – infiltration, evapotranspiration, runoff, percolation – for watershed areas ranging in size from a farm to several counties given local meteorological inputs. This paper reports the effectiveness of a widely-used computer model “SWAT” (Soil Water Assessment Tool) in predicting the components of the hydrologic cycle using soil properties derived from the field study compared to book values taken from other places at other times. The paper also looks at predictions of what happens to field-applied chemicals.

Technical Abstract: The effects of soil and water conservation practices on water quality are being simulated with hydrologic simulation models. Input parameters for physically-based models are commonly taken from generalized property data when field-measured data are unavailable. However, field-measured input parameters provide a higher level of assurance that model output uncertainty will be affected by model structure rather than by input parameter uncertainty. The measured effects of strip tillage on infiltration-runoff characteristics, soil available water capacity, soil organic matter and carbon, and soil bulk density from six 0.2 ha plots located near the Little River Experimental Watershed near Tifton, Georgia were used to determine separate sets of SWAT input parameters for strip and conventional tillage types for a cotton-peanut crop rotation. SWAT model calibration runs were performed for the two tillage types to compare simulated hydrologic and pesticide outputs to measured values. The implications of using generalized input data to estimate impacts of conservation measures in national assessments are discussed.

Last Modified: 8/29/2014