Calibration, validation, and evaluation of the Water Erosion Prediction Project (WEPP) model for hillslopes with natural runoff plot data

Authors: WANG, SHUYUAN - Purdue University; MCGEHEE, RYAN - Purdue University; GUO, TIAN - Purdue University; Flanagan, Dennis; ENGEL, BERNARD - Purdue University

Submitted to: International Soil and Water Conservation Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2022
Publication Date: 10/25/2022
Citation: Wang, S., McGehee, R.P., Guo, T., Flanagan, D.C., Engel, B.A. 2022. Calibration, validation, and evaluation of the Water Erosion Prediction Project (WEPP) model for hillslopes with natural runoff plot data. International Soil and Water Conservation Research. https://doi.org/10.1016/j.iswcr.2022.10.004.
DOI: https://doi.org/10.1016/j.iswcr.2022.10.004

Interpretive Summary: Soil erosion by water is a worldwide problem that decreases productivity of agricultural soils and can contribute sediment and pollutants to off-site water bodies. Management of croplands to control and reduce soil loss is an important priority, but baseline erosion rates and effects of different cropping and conservation management practices need to be determined in order to provide potential alternatives to farmers and landowners. Most commonly, soil erosion prediction models are used to estimate soil loss under different management systems. In this study we tested the performance of a process-based soil erosion tool, the Water Erosion Prediction Project (WEPP) model, at how well it could estimate water runoff and soil erosion compared to measured experimental data. We used data from 21 locations across the U.S. with detailed measurements and also detailed cropping and tillage information. Overall the WEPP model performed well at estimating average annual soil loss, which is the value used by conservation agencies when examining alternative cropping/management systems to control erosion. The model also performed very well at predicting average annual water runoff. Model performance decreased when going to finer time scale simulations. These results impact federal and state conservation agency personnel, landowners, farmers, and others with interest in soil erosion prediction technology performance.

Technical Abstract: The Water Erosion Prediction Project (WEPP) model has been widely used for estimating runoff and soil loss. The evaluation of the latest version (version 2021.133) under a range of environmental conditions can provide confidence to its users. The objectives of this study were to evaluate the WEPP model for runoff and soil loss predictions using 1255 plot years of data from field experimental plots with various climates, soils, topographies, and crops. WEPP runoff and soil loss predictions were compared to the observations before and after input parameter calibration. The results showed good predictions of runoff and soil loss were obtained with both the uncalibrated and calibrated WEPP model, with Nash-Sutcliffe model efficiencies (NSE) over 0.7 for average annual estimates. The calibration of input baseline effective hydraulic conductivity (ke), baseline critical shear stress (TauC), baseline rill erodibility (kr), and baseline interrill erodibility (ki) improved WEPP model performance with the NSE values of 0.94 and 0.81 for average annual runoff and soil loss predictions, respectively. The WEPP model tended to underestimate the runoff and soil loss for large events with runoff over 100 mm and soil loss over 120 t/ha. Good annual runoff and soil loss predictions (NSE greater than 0.4) were obtained for the most common cropping/management systems considered including tilled fallow, corn, wheat, and cotton. This study illustrates the most recent WEPP model’s performance for runoff and soil loss predictions, and provides a comprehensive set of results.