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Title: Adapting WEPP (Water Erosion Prediction Project) for forest watershed erosion modeling

item DUN, S
item WU, J
item ELLIOT, F
item Flanagan, Dennis

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 10/17/2006
Publication Date: 12/11/2006
Citation: Dun, S., Wu, J.Q., Elliot, F.S., Robichaud, P.R., Flanagan, D.C. 2006. Adapting WEPP (Water Erosion Prediction Project) for forest watershed erosion modeling. American Geophysical Union. December 11-15, 2006, San Francisco, CA.2006 CDROM.

Interpretive Summary:

Technical Abstract: There has been an increasing public concern over forest stream pollution by excessive sedimentation resulting from human activities. Adequate and reliable erosion simulation tools are urgently needed for sound forest resources management. Computer models for predicting watershed runoff and erosion have been developed during the past. These models, however, are often limited in their applications due to inappropriate representation of the hydrological processes involved. The Water Erosion Prediction Project (WEPP) watershed model has proved useful in certain forest applications such as modeling erosion from a segment of insloped or outsloped road, harvested units, and burned units. Nevertheless, when used for modeling water flow and sediment discharge from a forest watershed of complex topography and channel systems, WEPP consistently underestimates these quantities, in particular, the water flow at the watershed outlet. The main purpose of this study was to improve the WEPP watershed model such that it can be applied to adequately simulate forest watershed hydrology and erosion. The specific objectives were to: (1) identify and correct WEPP algorithms and subroutines that inappropriately represent forest watershed hydrologic processes; and (2) assess the performance of the modified model by applying it a real forested watershed in the Pacific Northwest, USA. In modifying the WEPP model, changes were primarily made in the approach to, and algorithms for modeling deep percolation of soil water and subsurface lateral flow. The modified codes were subsequently applied to Hermada watershed, a small watershed located in the Boise National Forest in northern Idaho. The modeling results were compared with those obtained by using the original WEPP and the field-observed runoff and erosion data. Conclusions of this study include: (1) compared to the original model, the modified WEPP more realistically and properly represents the hydrologic processes in a forest setting; and (2) application of the modified model produced satisfactory results, demonstrating the adequacy of the model modifications.