Spatial and temporal variability of rainfall erosivity factor for Switzerland

摘要

Rainfall erosivity, considering rainfall amount and intensity, is animportant parameter for soil erosion risk assessment under future land useand climate change. Despite its importance, rainfall erosivity is usuallyimplemented in models with a low spatial and temporal resolution. The purposeof this study is to assess the temporal- and spatial distribution of rainfallerosivity in form of the (Revised) Universal Soil Loss Equation R-factor forSwitzerland. Time series of 22 yr for rainfall (10 min resolution) andtemperature (1 h resolution) data were analysed for 71 automatic gaugingstations distributed throughout Switzerland. Regression-kriging was used tointerpolate the rainfall erosivity values of single stations and to generate a map forSwitzerland. Latitude, longitude, average annual precipitation, biogeographicunits (Jura, Midland, etc.), aspect and elevation were used as covariates, ofwhich average annual precipitation, elevation and the biographic unit(Western Central Alps) were significant (p<0.01) predictors. The mean value oflong-term rainfall erosivity is 1330 MJ mm ha−1 h−1 yr−1 with a range oflowest values of 124 MJ mm ha−1 h−1 yr−1 at an elevated station in Grisons tohighest values of 5611 MJ mm ha−1 h−1 yr−1 in Ticino. All stations havehighest erosivity values from July to August and lowest values in the wintermonths. Swiss-wide the month May to October show significantly increasingtrends of rainfall erosivity for the observed period (p<0.005). Only in February a significantly decreasingtrend of rainfall erosivity is found (p<0.01). The increasing trends ofrainfall erosivity in May, September and October when vegetation cover is scarce arelikely to enhance soil erosion risk for certain agricultural crops and alpinegrasslands in Switzerland.