Purdue University, Agricultural & Biological Engineering Department, West Lafayette, IN, USA.
University of Idaho, Soil & Water Systems Department, Moscow, ID, USA.
J Environ Manage. 2021 Aug 1;291:112616. doi: 10.1016/j.jenvman.2021.112616. Epub 2021 May 5.
The Water Erosion Prediction Project (WEPP) model has been widely used to assess the impacts of management practices and climate change on runoff and soil loss at both hillslope and watershed scales. However, the representation of channel erosion processes in WEPP has not been changed significantly since it was released. The current (WEPP v2012.8) and previous WEPP versions assume that channel input erodibility parameters are constant through time, which may lead to erroneous channel detachment predictions, especially for cropland with substantial tillage operations. In this research, the temporally constant values of channel erodibility and critical shear stress were replaced by daily updated values, using the same temporal erodibility and critical shear stress adjustments that are applied in hillslope profile simulations for rill detachment. Observed watershed-scale runoff and soil erosion data from six agricultural watersheds were used to calibrate and compare the WEPP model performance in simulating channel runoff volumes and soil losses before and after the modification. The research showed both WEPP v2012.8 and the modified WEPP model (WEPP_CE) could satisfactorily simulate event-based hydrology and soil erosion at the watershed outlets after calibration. The WEPP_CE model with temporally varying channel erodibility and critical shear stress values demonstrated improved representation of the physical processes in channel soil detachment. Continued improvement in the representation of channel erosion processes in WEPP and other process-based models is needed. The improved WEPP model can be used to evaluate the effectiveness of soil conservation practices on hydrology and erosion in further research.
水蚀预测项目（WEPP）模型已被广泛用于评估管理实践和气候变化对坡面和流域尺度的径流量和土壤流失的影响。然而，WEPP 中渠道侵蚀过程的表示自发布以来并没有发生重大变化。当前（WEPP v2012.8）和以前的 WEPP 版本假设渠道输入可蚀性参数随时间保持不变，这可能导致渠道分离预测错误，特别是对于有大量耕作作业的耕地。在这项研究中，使用与在斜坡剖面模拟中用于沟蚀分离的相同的时间可蚀性和临界剪切应力调整，用每日更新的值代替了渠道可蚀性和临界剪切应力的时间常数值。使用六个农业流域的流域尺度径流量和土壤侵蚀观测数据对 WEPP 模型进行校准和比较，以模拟修改前后渠道径流量和土壤流失的性能。研究表明，WEPP v2012.8 和修改后的 WEPP 模型（WEPP_CE）在经过校准后都可以很好地模拟流域出口处基于事件的水文学和土壤侵蚀。具有时间变化的渠道可蚀性和临界剪切应力值的 WEPP_CE 模型更好地表示了渠道土壤分离的物理过程。需要进一步改进 WEPP 和其他基于过程的模型中渠道侵蚀过程的表示。改进的 WEPP 模型可用于在进一步的研究中评估水土保持措施对水文和侵蚀的有效性。
