Steps Towards the Validation of Process-based Long-term Soil Redistribution at the Watershed Scale Using QGeoWEPP

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The Water Erosion Prediction Project (WEPP) is a process-based, semi-distributed parameter, one-dimensional, continuous model based on hydrology, erosion mechanics, plant growth, and open channel hydraulics. Due to the extensive requirement for data, the preparation of parameter settings for WEPP is time-consuming. QGeoWEPP is designed to be released as an open-source QGIS-based Geo-spatial Interface for WEPP offering the opportunity for community-based upgrades and user-based customization while having validation data sets to verify the validity of the upgrades. The model construction is shown in Figure 1. <fig><graphic xlink:href=23044_files/23044-05.jpg id=ID_12e6244d-640b-4a79-8627-5b709ff43400></graphic></fig> In this study, QGeoWEPP was used to analyze the spatial and temporal changing patterns of soil redistribution and sediment yield in the time period from 1963 to 2017 at the Lucky Hills site of the Walnut Gulch Experimental Watershed (WGEW), near Tombstone, Arizona (USA). Fifty-five model simulations were conducted in order to obtain detailed spatial distribution of soil redistribution for each year. Single year annual soil redistribution rate was calculated using the simulation results of two adjacent years. Both the spatial distribution of soil loss and deposition were analyzed separately, corresponding with the changing patterns of accumulated event-based sediment yield. The spatial distribution of soil loss and deposition rates could be classified into four types of patterns. Both the soil redistribution rates and the sediment yield were highly dependent on the number of significant rainfall events within each year. The detailed analysis of the spatial and temporal distribution of soil loss/deposition, as well as the event-based sediment yield accumulation can potentially provide an approach and guidance to the study of soil conservation within a relatively small watershed.