Assessment of Surface Runoff and Soil Loss During Highland Rice Growing in Mae Fah Luang District, Chiang Rai, Using the Water Erosion Prediction Project Model

Abstract

The objective of this research was to study surface runoff and soil loss as predicted by the Water Erosion Prediction Project Model (WEPP) and compare with results for surface runoff and soil loss based on actual measured data for different soils and with consideration of water conservation measures. The field research was conducted on terraced rice fields in the Mae Fah Luang district of Chiang Rai. The experiment used Randomized Complete Block Design (RCBD) with 7 treatments and 3 replications, which were: 1) highland rice planted no soil and water conservation measures (WOSC), 2) highland rice planted with ditches with a vertical interval of 4 meters between ditches (WH4M), 3) highland rice planted with ditches with a vertical interval of 8 meters between ditches (WH8M), 4) highland rice planted with ditches with a vertical interval 4 meters between ditches and with strips of vetiver grass planted outside the ditch (WHV4M), 5) highland rice planted with ditches with a vertical interval of 8 meters between ditches and with strips of vetiver grass planted outside the ditches (WHV8M), 6) highland rice planted with ditches and a vertical interval of 4 meters between the ditches and with strips of Assam tea planted outside the ditches (WHT4M), and 7) highland rice planted with ditches and a vertical interval of 8 meters between the ditches and with strips of Assam tea planted outside the ditches (WHT8M). The results showed that the values for runoff and soil loss as predicted by the model and those obtained from field measurement, when analyzed for difference by Root Mean Square Error (RMSE), were nearly the same. The amount of runoff as predicted by the model was 0.11-0.45 times higher than that actually measured, and the amount of soil loss predicted by the model was about 0.03-0.3 times higher than soil loss measured in the field.