Monthly Rainfall in Moroccan Arid Oasis Regions (1940-2017): Homogenization and Trends

Abstract

Reliable, high-quality climatic time series are essential for assessing climate change and its potential impacts, particularly in arid environments characterized by fragile natural resources, especially water resources. This study aims to perform quality control, reconstruction, and homogenization of monthly rainfall data for arid oasis basins in Morocco over the period 1940-2017. The Climatol homogenization algorithm was applied to data from local meteorological stations in order to construct a long-term, homogeneous, and coherent rainfall database suitable for climatic, hydrological, and environmental studies. Monthly rainfall trends were subsequently analysed using the non-parametric Mann-Kendall test. The results reveal contrasting trends depending on the month of the year, geographical location, and altitude. Stations located on the south-western flanks of the study area at low altitudes, exhibited increasing rainfall trends during certain months, whereas stations situated on the north-eastern flanks at higher elevations, were characterized by decreasing rainfall trends. This spatial opposition in rainfall trends is much more pronounced during the warm months, from May to August. These findings highlight the complexity of rainfall dynamics in Morocco’s arid oasis regions and provide essential insights into recent precipitation variability. They constitute an important scientific basis for decision-makers and water resource managers in developing appropriate strategies for sustainable water management in the study area.