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WEPP-GIS: Detailed Assessment of Soil Erosion, Runoff, and Sedimentation in Farm Fields and Small Watersheds

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Soil Erosion Research Under a Changing Climate, January 8-13, 2023, Aguadilla, Puerto Rico, USA  .(doi:10.13031/soil.23059)
Authors:   Olaf David, Jack R Carlson, Lucas Yaege, Holm Kipka, Dennis C Flanagan, James R Frankenberger
Keywords:   Erosion, Geospatial, Modeling, Web-based GIS, WEPP.

Abstract

The Water Erosion Prediction Project (WEPP) model applies processes for water infiltration, soil water percolation, surface runoff, evapotranspiration, raindrop and shear stress soil detachment, sediment transport and deposition, plant growth, residue management and decomposition, and irrigation in simulations to assess the impact of cropping system management on soil and water resources. Extensive use of WEPP on agricultural land usually involves defining a hillslope representing an entire farm field, often for the most erosive soil in the field, good enough for planning purposes. These assessments do not provide a detailed view of soil detachment and flow of water and sediment within the field, thus not providing sufficient information to support precise design, placement, and application of conservation practices. Further, they do not route water and sediment in water courses through a farm or the farms in a small watershed, thus not providing a more detailed view above the field scale. The WEPP spatial application (WEPP-GIS; Figure 1), deployed as a web model service and integrated with Catena-GIS and the Cloud Services Integration Platform (CSIP), provides two options for simulating soil erosion, runoff, and sediment transport: field-flowpath and watershed-flowpath.

Field mode simulates all flowpaths within a farm field. A CSIP service employs TauDEM (Tarboton, 2014), utilizes the USGS National Elevation Dataset 10-meter DEM, and clipping to create three delineation input layers: sub-watersheds, stream networks, and all flowpaths in the fields of a farm. Other CSIP services fetch parameters from common domain data sources to create soil and climate input layers. Users define the management of each field using CSIP services to fetch data from a common cropping system domain database to create the management input layer and crop rotation object to be used by the model. The WEPP model simulates each flowpath, iterating through each cell to the edge of the field. With watershed-flowpath mode the user specifies an outlet point on a channel cell, and a CSIP service delineates a traditional watershed above the outlet point, creating a network of sub-watersheds and channels not bounded by farm field boundaries. The CSIP delineation service defines all flowpaths within each sub-watershed, and the model simulates all flowpaths, water and sediment reaching the channel network and routing to the outlet. Large farms and small watersheds can involve a very large number of flowpaths, therefore to the maximum extent possible, simulations are run in parallel to reduce total run-time. Model output is aggregated and rendered to a variety of reports, maps, and graphs informing analysis leading to improved field/farm management alternatives.

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