Quantitative analysis and mapping of morphometric characteristics and water erosion in the watersheds of the Mediterranean region: application to the case of northern Algeria.

RESEARCH PAPER

Abstract

Water erosion, a complex and frequent phenomenon in the Mediterranean zone, particularly in northern Algeria, is the leading cause of soil degradation and affects water quality. A semi-arid climate threatens agricultural lands, increases sediment transport, and leads to the silting of dams. This study is based on data provided by the National Agency for Hydraulic Resources, covering 132 hydrometric stations. The analysis of liquid and solid discharges showed that the power model is the most suitable for assessing water erosion at different temporal scales. The average annual specific erosion varies from one watershed to another, generally ranging between 11.75 and 5978.34 t km^-2 yr^-1. The monthly distribution of solid inputs reveals that autumn is the season when solid transport reaches its peak in the majority of the studied watersheds, accounting for 38.93% of the total volume. Winter follows with a notable contribution of 28.27%, while spring records 25.26%. In contrast, summer is marked by the lowest flows, accounting for only 7.54% of the total transport. Principal component analysis (PCA) made it possible to distinguish four hydrologically homogeneous groups. Multiple regression was then performed on these groups to highlight a log-linear (Poisson) relationship between specific erosion and various explanatory variables, mainly the morphometric characteristics of the watersheds. The mapping of specific erosion in northern Algeria will be an essential tool for identifying the area’s most vulnerable to erosion. By providing a detailed assessment of the at-risk areas, this mapping will offer a clear vision of the sectors requiring priority interventions