ESTIMATING SNOWMELT RUNOFF EROSION INDEXES FOR CANADA

Rainfall and runoff erosion indices are required for soil water erosio n prediction using the Universal Soil Loss Equation. Valid estimates o f rainfall erosion indices are widely available for agricultural areas of Canada. Indices based on winter precipitation have been proposed b ut a better understanding of their relationship to runoff is required. Snowmelt runoff is defined as the runoff that occurs when there is sn ow cover. It may be more directly related to soil erosion than winter precipitation because little or no erosion is caused by the impact ene rgy of snowfall or rainfall on snow. Previous work has produced a comp uter model to estimate snowmelt runoff from available climatological d ata. In this study we review techniques that have been used to estimat e a runoff erosion index, adn use model estimates of snowmelt runoff t o 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 in dices. It is found that all the approaches currently used to estimate runoff erosion indices are highly correlated, but require empirical ad justment to select the winter period.