Assessing rainfall erosion risk in southern Saskatchewan from daily rainfall records
de Jong, E.
A mean annual rainfall erosion index (R1daily) calculated from daily rainfall records satisfactorily compared with the mean annual erosion index (R) calculated using the more accepted method with hourly rainfall records. An R1daily contour map of Southern Saskatchewan was constructed from a greater number of weather stations keeping daily rainfall records compared to the R contour map constructed from very few stations that keep hourly rainfall records. It was concluded that the R1daily contour map provided a more reliable assessment of rainfall erosion potential than the R contour map because the former distinguished local areas with high values and interpolation of rainfall risk involved much shorter distances between point measurements. Since significant erosion requires a combination of rainfall detachment as well as runoff, a runoff model that operated from daily climatic records was used to determine which days with rainfall also produced runoff. The runoff model was run for 62 stations in southern Saskatchewan and only days that produced runoff were included in the annual erosion index total. This effective erosion index (Reff) varied from 3.4 to 83.9 % of R1daily and was particularly sensitive to soil texture. Heavy-textured soils were, on average, more than four times as susceptible to water erosion than light-textured soils. It should be noted that the analysis does not include the effects of slope length and steepness, the crop canopy nor soil erodibility.
Soils and Crops Workshop