Rainfall Variability and Soil Erosivity in Semi-Arid Regions: Case of the Western Algerian Region

Abstract

This study analyzes some rainfall-related indexes in the Macta basin in northwestern Algeria, in the Orano-Mediterranean region, such as the Precipitation Index, Precipitation Concentration Index and Modified Fournier Index. Multi-factorial statistical tests were used to assess relationships between different geographic variables and precipitation parameters, based on the acquisition of monthly rainfall series from 42 stations in the catchment area, and that over 41 years. The objective of this article is to study the influence of rainfall parameters on rain erosivity in a semi-arid region (western Algeria) based on monthly rainfall series from different sites covering Macta watershed. Thus, establishing a relation between the monthly precipitaions and the energy of the rainfall intensities (EI30). The multifactorial analysis showed significant relations between the variables studied by grouping them with the same trends on the factorial axes. It was founded that the longitude-latitude-modified Fournier index group was on the same factorial axis, while the mean annual precipitation and altitude were on the other side. Altitude and latitude are the most important variables that govern the spatial distribution and variation of annual and interannual precipitation. The use of the monthly rainfall enabled to overcome the constraints of the rainfall intensities, the Precipitation-Modified Fournier Index relationship proved to be useful, showing the importance of the monthly average rainfall in the erosivity intensification.