Temporal distribution of runoff and soil erosion at a site in northeastern Oregon

ABSTRACT:

Average annual erosion predictions have marginal success in the Pacific Northwest perhaps because of variability of natural features related to runoff and soil erosion. Hydrologic frequency analysis and probability theory were used to analyze 12 years of runoff and erosion data from continuous fallow, fall-seeded winter wheat, and fall-plowed wheat stubble at a site in eastern Oregon. Relatively rare events are the major contributors to long-term soil losses for both discrete erosion events and seasonal erosion volumes, the soil loss tolerance for this soil type was never exceeded for discrete events on either the fall-seeded winter wheat or fall-plowed wheat stubble. Seasonal soil loss exceeded the soil loss tolerance in only one of twelve years for winter wheat and was never exceeded for the fall-plowed treatment. Soil losses over the long-term should not exceed soil loss tolerance values at this site under the soil management conditions used during this experiment.