Rainfall erosivity and soil crusting effects on large water erosion events in Central Chile

Rocío Céspedes, Carlos Bonilla

Wednesday 1 july 2015

11:15 - 11:30h at Oceania Foyer (level 0)

Themes: (T) Hydro-environment, (ST) Impacts of pollutants on the water environment

Parallel session: 9H. Water resources - Catchment

Soil erosion by water is a discrete process that is mainly controlled by a small number of extreme events. This process is also affected by soil properties and land use. The aim of this study was to characterize the largest soil loss events in Central Chile and the effects of soil crusting in the occurrence of these events. The Water Erosion Prediction Project (WEPP) model was used with actual data of rainfall, temperature and soil properties measured at six sites. Two scenarios of land use management were modelled: One with soil surface crusting over the time and one with soil tillage every month to prevent the crusting. In both scenarios the top 5% of total erosive events produced more than 30% of total eroded soil in each site. These events were high in storm erosivity and runoff. Results showed that soil crusting reduces the number of erosive events as well as the amount of eroded soil. Under this condition, the size of the extreme events was mainly controlled by storm erosivity. When crusting was not allowed, runoff and soil erodibility must be considered in addition to storm erosivity in order to predict sediment delivery. These results reveal the impact of tillage operation on soil erosion and the convenience of using the extreme erosion events information when designing soil and water conservation practices.