Author
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Hagen, Lawrence |
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Submitted to: Soil Erosion for 21st Century Symposium
Publication Type: Proceedings Publication Acceptance Date: 1/3/2001 Publication Date: 10/3/2001 Citation: In: J.C. Ascough II and D.C. Flanagan, Proc. Int. Symp. Soil Erosion Research for the 21st Century, 3-5 January 2001, Honolulu, HI. St. Joseph, MI: pp 479-482. Interpretive Summary: For each storm, total, horizontal soil discharge at a distance of 180 m downwind was estimated from the upwind horizontal soil flux collected in sediment samplers for a selected series of 24 storms that occurred at Big Spring, TX from 1989 to 1997. The downwind soil discharge was divided by field length to estimate average soil loss each storm for a field 180 m in length. Measured wind speed data and both estimated and measured surface conditions were used as inputs to the Wind Erosion Predicition System (WEPS) erosion submodel to simulate the erosion events. Resonable agreement (R 2 = 0.65) was obtained between the estimated and simulated erosion values. Further improvements in agreement can likely be achieved by simulating both surface wetness and aggregate/crust stability as variable inputs to the erosion submodel using other WEPS submodels. Additional quality asssurance checks also need to be conducted on some of the measured dinput data proposed for use in the validation exercise for wind erosion models. Technical Abstract: The Global Change and Terrestrial Ecosytems Soil Erosion Network has conducted a model validation exercise for water erosion models. This paper reports on part of a project to conduct a similar exercise for wind erosion models. Soil loss measurements for selected storm events obtained over several years from and eroding field are compared to predictions from the Wind Erosion Prediciton System (WEPS) erosion submodel for the same events The field data were collected from a small (2.5) hectare), circular, cropland field at Big Spring, TX. with samplers arranged in vertical clusters to sample horizontal soil discharge passing a point. Weather data including wind speed, wind direction, solar radiation, relative humidity, air temperature, and rainfall also were collected onsite. Temporal field site characteristics that were measured periodically included surface roughness, plant/residue cover, and dry aggregate size distribution. A power-law curve was fitted to the measured point-discharged data in each erosion event to estimate soil leaving the field at a downwind distance of 180 m. The WEPS erosion submodel was used to calculate the threshold erosion friction velocity based on surface conditions and then simulate soil loss during periods when the speed exceeded that threshold. Measured and simulated erosion values were in reasonable agreement (R 2 = 0.65). Uncertainties in the input data as well as additional techniques to improve the predictions are discussed. |
