Comment on calibration, validation, and evaluation of WEPP with natural runoff plot data
Abstract
15 16 Wang et al (2022) undertook an evaluation of the Water Erosion Prediction Project (WEPP) 17 model on 134 USLE runoff and soil loss plots. Wang et al did not compare the capacities of 18 WEPP and USLE based models to predict soil loss. The importance of doing that on bare 19 fallow plots is illustrated here. Data from comparisons of WEPP, RUSLE2, and the USLE-M 20 undertaken by Kinnell (2017) demonstrated that both RUSLE2 and the USLE-M predicted 21 event soil losses on 4 historic bare fallow USLE plots in the USA better than WEPP. It is 22 apparent that because WEPP is a steady state model designed to model event soil loss for 23 ridged tillage cultivation, WEPP is in not well suited to predicting event soil losses from bare 24 fallow plots that are planar with rills occurring in some storms but not all storms.. Given that 25 calibrated WEPP does not model event soil losses on bare fallow USLE plots better than 26 either RUSLE2 or the USLE-M, the fundamental ability of WEPP to model event erosion 27 under natural rainfall must be questioned at this time. 28 29 30 Keywords: WEPP; RUSLE2; USLE-M; calibration; natural rainfall 31 32 33 2