WINTER RUNOFF AND EROSION FROM PACIFIC NORTHWEST USA CROPLAND

Authors: McCool, Donald; SAXTON, KEITH - FORMER USDA-ARS; KALITA, PRASANTA - UNIVERSITY OF ILLINOIS

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 3/17/2006
Publication Date: 7/9/2006
Citation: McCool, D.K., K.E. Saxton, and P.K. Kalita. 2006. Winter runoff and erosion on northwestern USA cropland. Pap. 062190. St. Joseph, MI.: ASABE.

Interpretive Summary: Much of the annual runoff and soil loss from non-irrigated cropland in the Inland Pacific Northwest U.S.A. is caused by rain and snowmelt on frozen and thawing soil. Quantifying the effects of these winter processes and their interaction with crop management is important for hydrologic model development, and for designing cropping systems to prevent erosion. Runoff plots under a number of cropping systems were installed at the Palouse Conservation Field Station near Pullman, WA in the fall of 1978. Frost, thaw, and snow depths were measured regularly. Runoff and sediment samples were obtained from collection tanks. This 18-year data set was supplemented with a 43-year data set obtained from monitoring winter erosion on a large number of sample fields in Whitman Co, WA from Water Year (WY) 1941 through WY 1982, to examine historic trends in erosion and corresponding climate conditions. During this 43-year period, the winter wheat/summer fallow rotation was used on much of the area, including the higher precipitation zone more suitable for annual cropping. Erosion was low during several consecutive years in the 43-year period. Weather records for these years indicate reduced freeze/thaw activity with little rain or snowmelt during thaw. Data analysis indicated that soil loss was not correlated with diurnal freeze-thaw cycles, or with annual snowfall, or with snow at the time of thaw. Event soil erosion was positively correlated with precipitation during thaw, as was annual erosion with annual precipitation. Crop management had a substantial effect on infiltration and runoff, and an even greater effect on erosion.

Technical Abstract: Much of the total annual runoff and soil loss from non-irrigated cropland in the Inland Pacific Northwest U.S.A. results from rain and snowmelt on frozen and thawing soil. Quantifying the effects of these winter processes and their interaction with crop management is important for hydrologic model development and calibration, and for designing cropping systems to prevent erosion. Runoff plots under a number of cropping systems were installed at the Palouse Conservation Field Station near Pullman, WA in the fall of 1978. Data was collected on the replicated treatments for 13 years, and from a smaller set of replicated treatments for another five years. Frost, thaw, and snow depths were measured regularly. Runoff and sediment samples were obtained from collection tanks. This 18-year data set was supplemented with a 43-year data set obtained from monitoring winter erosion on a large number of sample fields in Whitman Co, WA from Water Year (WY) 1941 through WY 1982, to examine historic trends in erosion and corresponding climate conditions. During this period, the winter wheat/summer fallow rotation was used on much of the area, including the higher precipitation zone more suitable for annual cropping. Erosion was low during several consecutive years in the 43-year data set. Weather records for these years indicate reduced freeze/thaw activity with little rain or snowmelt during thaw. Data analysis indicated that soil loss was not correlated with diurnal freeze-thaw cycles, or with annual snowfall, or with snow at the time of thaw. Event soil erosion was positively correlated with precipitation during thaw, as was annual erosion with annual precipitation. Crop management had a substantial effect on infiltration and runoff, and an even greater effect on erosion.