Soil Erosion Rates Via 210Pbex, 137Cs and USLE Model in El Rmel Watershed, NE Tunisia

Abstract

Soil erosion is a severe environmental and agricultural phenomenon which can be accelerated with climate change and land use, particularly in the Mediterranean region. In Tunisia, studies on the spatial distribution of erosion and deposition patterns can help to effectively implement soil and water conservation practices. Accordingly, the main objective of this research was to estimate soil erosion rates in two cultivated soils (SE1 and SE2), at El Rmel watershed of northeastern Tunisia. Three different time scales were observed via three tools, the ¹³⁷Cs, the ²¹⁰Pb_ex radioisotopes and the USLE model. The FRN's conversion mass balance model 2 (MBM2) was used to convert activities into erosion rates. Based on the ¹³⁷Cs, ²¹⁰Pb_ex, and USLE model, the mean erosion rates were, respectively, 37, 52, and 33 t ha⁻¹ year⁻¹, at the cereal cultivated SE1 site and 4, 9, and 6 t ha⁻¹ year⁻¹, at the olive tree cultivated SE2 site. It is supposed that the difference in time scale expressed by the three methods (100 years by ²¹⁰Pb_ex, 60 years by ¹³⁷Cs, and 40 years by USLE), may have had a notable impact on the discrepancy in estimated erosion rates. The mean farm slope for SE1 and SE2 were, respectively, 14% and 8% and tillage was through three operations per year. Furthermore, the cereal crops site characterized by steep slopes show much higher erosion rates. Consequently, planting olive trees will be very helpful in reducing soil erosion and will be of great impact either environmentally and/or economically.