Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 18, 1995
Publication Date: N/A
Interpretive Summary: The WEPP technology is a tool for conservation planning. It is used to help farmers and land managers make appropriate decisions about how to manage the land to reduce soil erosion. It is also used to make erosion assessments and inventory, that is, to determine how much erosion is occurring on the land so that society as a whole can know how much soil is being lost to erosion and to make better decisions as to how land should be managed on a broad geographical scale. This study was undertaken to help the user select certain important data values related to climatic characteristics of the location of interest. We found that using data obtained at individual National Weather Service stations were not adequate. Because of various factors, including extremely localized weather patterns and differences in the length of the measured weather records at a location, variations in the WEPP computed soil loss from station to station were not realistic. Therefore, we developed a method to regionally evaluate trends in the weather data from station to station, which provides a much better picture of the overall trends in erosion across regions and states. This method will give the United States a much better and more consistent tool for conservation planning and erosion assessment.
Technical Abstract: The combination of the weather generator CLIGEN and the Water Erosion Prediction Project model WEPP provides a way to predict runoff and erosion for individual rainfall events for long periods of simulation. The purposes of this study were : 1) to investigate the required simulation period necessary to obtain stable long-term annual averages of soil erosion for various environmental conditions, 2) to investigate the effects of station-to-station variability of CLIGEN input data on the average annual soil loss predictions obtained from WEPP, and 3) to develop methodology for reducing unreasonable and undesirable levels of such variation while maintaining the integrity of the models in representing regional trends in erosion differences due to climate. The results showed high variations of the average annual soil loss results when the only changes in the input were the climate parameter values used by CLIGEN from one weather station to another for period longer than 50 years. For shorter periods (30 years) the annual variability of soil loss was larger than the variability induced by climate parameters and averaging these parameters does not improve the results. A comparison of equal soil loss contours obtained after averaging parameters and isoerodent lines from the RUSLE model shoed that both reveal similar trends. In mountainous regions, this model was not applied because changes in climate of two adjacent stations were sometimes abrupt.