ASSESSING SOIL EROSION SUSCEPTIBILITY FOR PAST AND FUTURE SCENARIOS IN
SEMI-ARID MEDITERRANEAN AGRO-ECOSYSTEMS
Abstract
The assessment of soil erosion rate, especially in agricultural lands,
represents a fundamental tool for land management planning in the
long-term period. In this study, the SWAT model was utilized to simulate
soil erosion within a semi-arid watershed in South Portugal. The model
was successfully calibrated and validated using real data of streamflow
and river sediment transport in four hydrometric stations. Soil erosion
susceptibility maps (historical and future) were realized to highlight
the evolution of the phenomenon through time. The historical period was
confirmed to be the worst one in terms of average soil erosion for each
land use, followed by the Representative Concentration Pathways (RCPs)
8.5 and 4.5 scenarios. The main differences in soil loss among the two
RCPs will be influenced by the slightly increasing trend of extreme
events which will characterize the RCP 8.5, leading to a higher maximum
value of soil erosion. Results highlighted the tendency to erosion of
Leptosols and of the agro-forestry system (“montado”), which
influenced the soil erosion susceptibility distribution of the whole
basin. The study confirmed that Leptosols are the most subject to
sediment loss due to their intrinsic characteristics, and that
“montado” and farmed systems will negatively influence soil erosion
rate if anti-erosion actions will not be adopted, stressing the need to
identify all aspects responsible for land degradation in Mediterranean
watersheds.