The daily rainfall dataset of 35 weather stations covering the north of Algeria was studied for a period up to 43 years, recorded after 1970s. The variability and trends in annual maximum daily rainfall (AMDR) time series and their contributions in annual rainfall (AR) were investigated. The analysis of the series was based on statistical characteristics, Burn’s seasonality procedure, Mann-Kendall test, and linear regression technique. The contribution of the AMDR to AR analysis was subjected to both the Buishand test and the double mass curve technique. The AMDR characteristics reveal a strong temporal irregularity and have a wide frequency of occurrence in the months of November and December while the maximum intensity occurred in October. The observed phenomenon was so irregular that there was no dominant season and the occurrence of extreme event can arrive at any time of the year. The AMDR trends showed that only six of 35 stations have significant trend. For other stations, no clear trend was highlighted. This result was confirmed by the linear regression procedure. On the contrary, the contribution of AMDR in annual totals exhibited a significant increasing trend for 57% of the sites studied with a growth rate of up to 50%.

Les résultats d'analyse graphique des valeurs instantanées des débits solides en suspension dans le cours d'eau de l'Oued Mouilah et leurs relations avec les débits liquides, durant les compagnes de prélèvements de 1977 à 1993, ont permis de montrer l'existence de deux périodes d'érosion actives. Le flux des matières solides en suspension dans le cours d'eau est très variable d'une année à une autre et la dégradation spécifique moyenne annuelle sur les 16 années d'étude est estimée à 126 tonnes par km². Cette valeur est relativement faible par rapport à celles trouvées pour d'autres régions à régime hydrologique similaire.

In this study, the spatial variation of daily and monthly concentration precipitation index and its aggressiveness were used in 23 rainfall stations in the extreme north-east of Algeria over the period 1970–2010. The trend was analysed by the Mann–Kendall (MK) test. The results show that daily precipitation concentration index (CI) values are noticeably higher in places where the amount of total precipitation is low, the results of MK test show that areas of high precipitation concentration tend to increase. The seasonality and aggressiveness of precipitation are high in the eastern and western parts of the study region (eastern and central coastal of Constantine catchments), whereas a moderately seasonal distribution with low aggressiveness is found in the middle of the study area (plains and central Seybouse catchment). As a result, the modified Fournier index (MFI) has a significant correlation with annual precipitation, whereas theCIand monthly precipitation concentration index (PCI) show an opposite correlation in relation to annual precipitation.

The Maghreb is a mountainous region subjected to a contrasting climate with wind storms in summer and unpredictable rainfall fluctuation both throughout the year and from year-to-year. Rainfall in the area is often intense on dry soils with poor vegetation. Intense rainfall events rapidly generate strong surface runoff that removes large quantities of soil. However, few studies have examined the processes controlling soil erosion in the Maghreb area and it is in this context that this study was done. The research presented is based on a detailed analysis of suspended sediment loads and water flow at the outlet of the Upper Tafna basin (256 km²) in northwest Algeria, based on a monitoring programme from September 1988 to August 1993. The results show that the increased aridity leads to an increase in the erosive potential. Marked hysteresis is observed between suspended sediment loads and water flow. The nature of the hysteresis is variable and the various types of hysteresis are used to characterise the various mechanisms of erosion and transport that operate in the area and show the importance of the storage of previous sediment deposits in the river. Résumé Le Maghreb est une région montagneuse o[ugrave] règne un climat contrasté avec des orages en été et une variabilité imprévisible de la pluie à la fois intra- et inter-annuelle. La pluie dans la région est souvent intense, sur des sols secs et une végétation pauvre. Les événements pluvieux intenses génèrent rapidement un important ruissellement qui emporte de grandes quantités de sol. Cependant, peu d'études ont examiné les processus qui contrôlent l'érosion des sols au Maghreb et c'est dans ce contexte que s'inscrit notre contribution. La recherche présentée s'appuie sur une analyse détaillée des débits liquides et des charges solides en suspension mesurés à l'exutoire du bassin versant de la Haute Tafna (256 km²) situé dans le nord ouest de l'Algérie, lors d'un programme de suivi qui a couvert la période Septembre 1988–AoÛt 1993. L'étude révèle que l'accroissement de l'aridité augmente le potentiel érosif. Une nette hystérésis est observée entre la charge solide et le débit liquide. La nature de l'hystérésis est variable. Les différents types d'hystérésis sont utilisés pour caractériser les différents mécanismes d'érosion et de transport qui opèrent dans la région, et mettent en évidence l'importance de la remise en suspension des dépôts sédimentaires antérieurs dans le cours d'eau.

This study aims to provide a brief overview of four regional climate model (RCM) estimations for (Daily, Monthly, Seasonal, and Annual) averaged precipitation over the Wadi Chemora Basin in northeastern Algeria for the historical period (1970–2005) and future forecasts (2006–2100). Data from seven ground stations were compared to data from four RCMs: RCA4 driven by ICHEC-EC-EARTH and NOAA-GFDL-GFDL-ESM2M from MENA-CORDEX domain with intermediate resolution (25 km, 0.22°) and ALADIN and RegCM4 from MED-CORDEX domain with high resolution (12 km, 0.11°). In most time steps (Annual, Seasonal, Monthly, and Daily), the raw RCMs overestimated precipitation, but their performance improved significantly after applying gamma quantile mapping (GQM) bias correction method. The bias-corrected projections indicate decreases of seasonal rainfall for the near future (2010–2039), mid-century (2040–2069), and end of century (2070–2100) periods. Overall decreases in all seasons lead to the projected decrease in annual rainfall of an average of 66% by the end of the 21st century.