Submitted to: ASABE Annual International Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2006
Publication Date: 3/15/2007
Citation: Dun, S., Wu, J.Q., McCool, D.K. 2007. Improving WEPP Winter Hydrology. ASABE Annual International Meeting.
Technical Abstract: The Palouse area of the Northwestern Wheat and Range Region in southeastern Washington, northern Idaho, and north-eastern Oregon has serious winter erosion problems due to recurring rainfall and snowmelt runoff on freezing and thawing soil. The Water Erosion Prediction Project (WEPP) model has proved its ability in modeling runoff and erosion for many agricultural areas. However, when used for modeling water flow and sediment discharge from the Palouse, WEPP consistently underestimates these quantities, in particular, winter runoff. The goal of this study was to improve the WEPP model version 2006.5 such that it can adequately simulate winter hydrology and erosion. Specific objectives were to: (1) identify and correct apparent coding errors and modify winter sub-routines in WEPP v2006.5 to better represent winter hydrologic processes; and (2) verify the modified model. Changes were made in the codes for modeling snow accumulation and melt, and soil freezing and thawing. The modified codes were subsequently applied to data from runoff and erosion plots at the Palouse Conservation Field Station (PCFS), Pullman, WA, and snow and frost data from plots near Morris, MN, USA. The model results were compared with those obtained using WEPP v2006.5 and the field-observed snow, soil frost, runoff and erosion data. Conclusions of this study include: (1) compared to the WEPP v2006.5, the corrected WEPP more realistically and properly represents the winter hydrologic processes of the Pullman and Morris field plots; and (2) application of the modified model produced satisfactory results, demonstrating the adequacy of the model modifications.