Estimating snowmelt runoff erosion indices for Canada

ABSTRACT: Rainfall and runoff erosion indices are required for soil water erosion prediction using the Universal Soil Loss Equation. Valid estimates of rainfall erosion indices are widely available for agricultural areas of Canada. Indices based on winter precipitation have been proposed but a better understanding of their relationship to runoff is required. Snowmelt runoff is defined as the runoff that occurs when there is snow cover. It may be more directly related to soil erosion than winter precipitation because little or no erosion is caused by the impact energy of snowfall or rainfall on snow. Previous work has produced a computer model to estimate snowmelt runoff from available climatological data. In this study we review techniques that have been used to estimate a runoff erosion index, and use model estimates of snowmelt runoff to compare the indices and develop a new index more closely related to runoff than winter precipitation. Data from 54 climatological stations across Canada are used to evaluate and compare rainfall and runoff indices. It is found that all the approaches currently used to estimate runoff erosion indices are highly correlated, but require empirical adjustment to select the winter period.