Impacts of rainfall variability in Gharb plain: Morocco

Abstract

The Mediterranean climate is characterized by irregular rainfall, leading to both severe droughts and occasional flooding. This research aims to examine the changes occurring in the rainfall regime of the Gharb plain over thirty-three years, with specific attention given to three sites: El Menasra, Bel Ksiri, and Sidi Slimane. A range of methods were employed to understand the dimensions and impacts of rainfall in the study area. These methods include trend detection, testing for breaks, analysis of reduced annual anomalies, utilization of the Hyrfan Plus software, calculation of the Martone aridity index, assessment of the standardized rainfall index, and mapping flood zones. The findings of this study revealed that the Gharb Plain experienced periods of rainfall deficits, resulting in drought conditions during years with below-average rainfall. Conversely, years with above-average rainfall exhibited severe flooding, indicating the occurrence of two extreme phenomena that necessitate effective hydraulic management strategies. The main results showed that the rainfall trend is regressing, as the Nicholson, Martone, Emberger, and standardized precipitation indexes justify this regression. In addition, the plain has received an immense quantity of water from the Rif and Atlas Mountains, with the result that the study area has from time to time experienced severe flooding, as shown by the return periods detected, The Gharb plain has therefore experienced a rainfall deficit (drought) in years with below-average rainfall, while years with above-average rainfall have seen severe flooding, putting the country under two extreme phenomena requiring hydraulic management.