WEPPCLIFF: A command-line tool to process climate inputs for soil loss models

Authors: MCGEHEE, RYAN - Purdue University; Flanagan, Dennis; SRIVASTAVA, PUNEET - Auburn University

Submitted to: Journal of Open Source Software
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2020
Publication Date: 5/11/2020
Citation: McGehee, R.P., Flanagan, D.C., Srivastava, P. 2020. WEPPCLIFF: A command-line tool to process climate inputs for soil loss models. Journal of Open Source Software. 5(49):2029. https://doi.org/10.21105/joss.02029.
DOI: https://doi.org/10.21105/joss.02029

Interpretive Summary: Soil erosion by water is driven by rainfall and runoff processes, which in turn are affected by land management and crops grown, and environmental factors affecting the plant growth (mainly precipitation, temperatures, and solar radiation). Erosion prediction computer simulation models are often used to estimate potential soil loss, and a major input to these is daily weather information including rainfall occurrence, rainfall depth, rainfall intensity, maximum air temperature, and minimum air temperature. The Water Erosion Prediction Project (WEPP) model simulates soil erosion by raindrop impact and overland flow, as well as associated crop growth and biomass production. A stochastic weather generator called CLIGEN (CLImate GENerator) is commonly used with WEPP to generate a string of synthetic daily weather values for erosion model simulations, based upon long-term weather station statistics. Another option for WEPP is to utilize actual observed rain storm inputs, that provide more accurate information on rainfall intensity and storm occurrence, rainfall amount and storm duration. A new software program called WEPPCLIFF (WEPP CLImate File Formatter) provides an easy tool to convert observed recording raingage data and other weather station information into WEPP breakpoint climate input files. This paper and the associated open source software is provided, to assist erosion model users and others that may have a need to process and use observed weather station information for their applications. This work impacts scientists, faculty, students, and others utilizing observed precipitation data in erosion or other modeling applications.

Technical Abstract: A key driver of erosion and arguably the most labor-intensive input to erosion models, especially the Water Erosion Prediction Project (WEPP) model, is climate. Even the simplest erosion models require climate inputs which are not always straightforward in their calculation. The complexity of these inputs dissuades potential users from creating their own inputs from observed data, which are almost always better than their simulated counterparts, especially when used to force erosion models for historical periods. For example, the Revised Universal Soil Loss Equation version 2 (RUSLE2) and WEPP are two of the leading soil erosion prediction models in the world today, but both still rely on climate inputs that are either outdated or simulated. RUSLE2 as currently applied commonly within the United States relies on climate data from 1960-1999, which is not only 20 years out of date, but the years that utilized had fewer observation stations and the stations themselves used a mix of older technologies, some of which have documented quality issues that impact usability and reliability. WEPP on the other hand, just had its database updated to the years 1974-2013, but those observed values are only used to create parameter files for CLIGEN (CLImate GENerator) which is then used to create simulated climate files for WEPP. In short, the erosion modeling community can do better, and our users are in need of software that can at least shoulder most of the burden when preparing climate inputs for popular soil loss models. Hence the need for WEPPCLIFF (WEPP CLImat File Formatter). WEPPCLIFF is an R-based command line tool which was originally designed to prepare climate inputs for WEPP, that has been extended to perform other general functions such as quality checking, gap filling, and erosion index calculations (climate inputs for USLE family of models). The program is provided with accompanying documentation which walks a user through installation and a brief tutorial for application of the tool. A comprehensive section on syntax and accepted inputs is also provided in the documentation.