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United States Department of Agriculture

Agricultural Research Service

Research Project: Mitigating Agricultural Sources of Particulate Matter and Greenhouse Gas Emissions in the Pacific Northwest

Location: Land Management and Water Conservation Research

Title: Seasonal change of WEPP erodibility parameters for two fallow plots on a Palouse silt loam

Authors
item Mccool, Donald -
item Dun, Shuhi -
item Wu, Joan -
item Elliot, William -
item Brooks, Erin -

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 24, 2013
Publication Date: N/A

Interpretive Summary: Major erosion events in the Inland Pacific Northwest can occur as soil frozen during cold periods thaws and loses cohesive strength during warm-up and is easily detached and transported by rainfall or snowmelt. The success of any erosion model used to select crop management systems to provide erosion protection depends on properly estimating the occurrence and magnitude of these freeze/thaw events. Previous application of the WEPP (Water Erosion Prediction Project) model in southeastern Washington State showed that WEPP reproduced the occurrence of the large runoff events, but the sediment yield was not properly estimated. The objective of this study was to evaluate the seasonal changes of rill erosion parameters in southeastern Washington. Observed runoff and erosion events during 1984-1990 were used to estimate WEPP hydraulic and erosion parameters. Soil parameters were best-fit using WEPP single-event simulations to reproduce the observed runoff and sediment yield. The results indicate that modifying the relationships that describe the dynamic changes of detachment and transport factors for erosion of frozen and thawing soils can improve the performance of WEPP for use by federal and state agencies in estimating winter erosion and evaluating alternative crop management systems.

Technical Abstract: In cold regions, frozen soil can have a significant influence on runoff and water erosion. In the Inland Pacific Northwest U.S., major erosion events typically occur during winter as frozen soil thaws and exhibits low cohesion. The success of any erosion model used to select crop management systems to provide erosion protection depends on properly estimating the occurrence and magnitude of these freeze/thaw events. Previous application of the WEPP (Water Erosion Prediction Project) model to a continuous bare tilled fallow (CBF) runoff plot at the Palouse Conservation Field Station (PCFS) in southeastern Washington State showed that WEPP reproduced the occurrence of the large winter runoff events, but the sediment yield was not properly estimated. The inability of WEPP to reproduce the magnitude of field-observed erosion events at the PCFS suggests need to examine the dynamic changes in soil erosion properties due to freeze-thaw and to improve the representation of such dynamics. The objective of this study was to evaluate the seasonal changes of rill erosion parameters for two CBF runoff plots at the PCFS. Field-observed runoff and erosion events during 1984-1990 were used to estimate WEPP hydraulic and erosion parameters, including soil effective hydraulic conductivity, critical shear stress, and rill erodibility. The parameters for each event were best-fit using WEPP single-event simulations to reproduce the observed runoff and sediment yield on both plots. The results indicate that modifying the relationships that describe the dynamic changes of detachment and transport factors for erosion of frozen and thawing soils can improve the performance of WEPP in estimating winter erosion.

Last Modified: 8/19/2014