Spatial and temporal rainfall variability and erosivity: Case of the Issen watershed, SW-Morocco

Abstract

The Issen basin is a dry area affected by climate variability and desertification. It is located in high spot of Moroccan flora biodiversity that includes argan tree ecosystem as a part of the Western High Atlas (WHA). The objective of this work is to assess rainfall variability and erosivity as determining factors of soil erosion and vegetation cover degradation. The results reveal an arid to superior semi-arid climate where annual rainfall range from 200 mm in the centre of the Argana corridor, to 500 mm in the snow-covered northern foothills. The analysis of the 37 years of rainfall data indicate a coefficient of variation Cvis about67%. The erosivity index presents a high variability range from 34 to more than 81 MJ.mm/ha.h.yr in the wettest areas, indicating considerable soil erosion. In addition, the basin suffering from severe periods of drought due to the occurrence of the continuous decrease of the accumulated precipitation. Eventually, the rainfall variability and erosivity can affect ecosystem function and services (ecosystem degradation, water availability, etc).