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Variabilité des précipitations annuelles du Nord-Ouest de l’Algérie
... Algeria is very vulnerable to potential climate change due to the significant spatial and temporal irregularity of water resources. It has experienced several droughts over the past century, particularly in the 1940s and 1970s (Meddi and Hubert 2003;Meddi and Meddi 2009;Meddi et al. 2010;Zeroual et al. 2017Zeroual et al. , 2019Meddi and Eslamian 2021). This situation has also been observed in the southern Mediterranean area, where Morocco and Tunisia have experienced a decrease in rainfall since the mid-1970s (Longobardi and Villani 2010;Marchane et al. 2017;Cramer et al. 2018;Tramblay et al. 2018;Hadour et al. 2020). ...
... According to the Koppen-Geiger climate classification, the plain has a Mediterranean climate with hot, dry summers and rainy winters (Peel et al. 2007;Zeroual et al. 2019). The average annual rainfall ranges between 500 and 700 mm, while the average temperature varies from 6 °C in winter to 33 °C in summer (Meddi and Meddi 2009;Boufekane et al. 2020). The Mitidja plain is formed by the juxtaposition of sub-basins drained from south to north by a dense hydrographic network (Fig. 1). ...
The scarcity of surface water resources has a significant impact on Mediterranean basin. This study aims to assess the climate change impacts on surface water resources in the Mitidja plain in Algeria. Two pre-calibrated monthly water balance models, namely, the GR2M model and the abcd model, were used. These models were driven by bias-corrected datasets from the fifth and sixth phases of the Coupled Model Intercomparison Project (CMIP5 and CMIP6) under two Representative Concentration Pathway scenarios (RCP4.5 and RCP8.5) and two Shared Socioeconomic Pathways (SSP2 and SSP5). The combined Box–Cox transformation and bootstrapping procedure was used to aggregate the multiple runoff projections generated. The results revealed significant variations in the runoff patterns across the different sub-basins. In addition, all scenarios indicated a reduction in projected runoff across all sub-basins of the Mitidja plain, spanning from 26 to 74.32%. Furthermore, CMIP6 simulations showed more intense changes over the Mitidja basin.
... In recent decades, the North African region has experienced a decrease in rainfall resulting in acute drought (Ghenim & Megnounif, 2011;Medjerab & Henia, 2011). In Algeria, rainfall deficits are estimated at between 20 and 50% (Aït Mouhoub, 1998;Meddi & Meddi, 2009). These not only induce a decrease in flows of up to 70% (Ghenim et al., 2010;Meddi & Hubert, 2003), but also an increase in soil susceptibility to erosion (Barthès & Roose, 2002;Megnounif & Ghenim, 2013;Scott, 2006). ...
... Strong El Niño events were observed in 1957-1958, 1965-1966, 1972-1973, 1987-1988, and 1991-1992, with 1982-1983, 1997-1998, and 2015-2016 being among the strongest ever recorded. Since 2000, weak El Niño events have been observed in 2002-2007, 2009-2010, 2018-2020(Null, 2020. In contrast, the La Niña phenomenon recorded strong events during the years 1973-1974, 1975-1976, 1988-1989-2000, 2007-2008-2011, and moderate events during 1955-1956, 1979-1981, 1995-1996(Null, 2020. ...
Rainfall erosivity is a critical factor affecting soil erosion and agricultural productivity. This study aims to analyze rainfall erosivity in the northern region of Algeria using a hybrid approach that combines empirical and modeling techniques. The primary objectives are to identify homogeneous regions, assess their susceptibility to climate change, and determine the wet and dry periods impacting the study area. Additionally, the modified Fournier Index (MFI) is calculated over 76-years (1941–2016) using data from 33 pluviometric stations. The results reveal distinct wet and dry periods in the study area, with abundant rainfall occurring in winter/autumn and spring, followed by a summer drought. The northern region exhibits high erosivity levels, ranging from severe to very severe, while the southeast and other regions experience low to moderate erosivity. Region 4 demonstrates the highest rain aggressiveness and moderate to severe erosion throughout the study period. Spatial analysis shows an increasing MFI gradient from west to east and south to north. Furthermore, the study establishes a positive correlation between MFI and the Southern Oscillation Index, indicating that El Niño and La Niña have a significant influence on sedimentary production. Overall, this research provides valuable insights into rainfall erosivity patterns in Northern Algeria, aiding in the identification of high-risk areas and supporting sustainable land management strategies.
... During the 40s and 70s to the present time, some of these droughts have had repercussions, sometimes dramatic, on the living conditions of the population. The most severe and persistent ones are those recorded during the years between 1980and 1990(Agoumi et al. 1999Laborde 1993 ;Haida et al. 1999 ;Meddi 2001 ;El Mahi 2002 ;Meddi and Hubert 2003 ;Bouanani et al. 2003 ;El Mahi et al. 2004 ;Ketrouci et al. 2004 ;Talia and Meddi 2004 ;Khaldi 2005 ;Bekkoussa et al. 2008 ;Meddi and Meddi 2009 ;Ghenim et al. 2010;Nouaceur et al. 2013;Belarbi et al. 2017;Gherissi 2018;Djellouli and Bouanani 2019). The work of Demmak (1982) showed that the magnitude of the rainfall deficit during the period 1974-1992 intensified from East to West, generating drought trends during the study period and showing similar droughts during the years 1913and 1940. ...
... The breaks mentioned above confirmed the evolution towards drought with a deficit ranging from 30 to 80 %. These breaks concern all (Laborde 1993;Meddi and Meddi 2009;Ghenim et al. 2010). The magnitude of the deficit recorded after the break results from the gradual change in the regime. ...
In recent decades, the problem of drought has been recognized as one of the major problems that generate negative impacts on the water resource, it is considered an obvious reality throughout the world. This drought is a natural phenomenon resulting from climatic variability, characterized by a lack of water over a sufficiently long period. The objective of this study is to highlight the existence of this phenomenon at the spatio-temporal scale, and assess its impact on the hydrological regime at the watershed of Oued Lakhdar over a period of 44 years using different statistical methods and drought indices. The application of the drought indices SPI, SSFI, IP and hydraulicity coefficient, over the period extending from 1970 to 2014, allowed to identify the wet and drought periods frequencies, as well as the excess and deficit flow frequencies. The 1980s, 1990s and 2000s appear to be deficient decades, with a noticeable rainfall return trend for the period (2008/2014). Results obtained by application of statistical methods indicate rainfall breaks between the period of 1976 - 1981, which mark a change in the rainfall and hydrological regime. These breaks are accompanied by a 24 % decrease in pluviometry and a 57 % decrease in water flow compared to the previous period (before the break). The occurrence of this climate variability has an impact on water resources. The watershed also experienced a rainfall decrease and a temperature increase over the period extending from 1982-2008.
... Around 13% of Algeria has a Mediterranean climate, and the watersheds of this region contribute to approximately 75% of the annual surface water flow [7] with a situation of water scarcity in dry periods [8]. A reducing trend of rainfall with an order of 20% in the northern center of Algeria was observed in the late 1970s [9], which led to a drastic decrease of stream flow by almost 55% in this region, and fluctuations from 61% to 71% brought a decline in stream flow in the extreme northwest [10] due to a reduction of more than 36% of rainfall [9]. The major cause of this phenomenon is due to the negative correlation between temperature and the North Atlantic oscillation and the tropical South Pacific Ocean oscillation represented by the climate index Nino4 (El Niño Southern Oscillation). ...
... Around 13% of Algeria has a Mediterranean climate, and the watersheds of this region contribute to approximately 75% of the annual surface water flow [7] with a situation of water scarcity in dry periods [8]. A reducing trend of rainfall with an order of 20% in the northern center of Algeria was observed in the late 1970s [9], which led to a drastic decrease of stream flow by almost 55% in this region, and fluctuations from 61% to 71% brought a decline in stream flow in the extreme northwest [10] due to a reduction of more than 36% of rainfall [9]. The major cause of this phenomenon is due to the negative correlation between temperature and the North Atlantic oscillation and the tropical South Pacific Ocean oscillation represented by the climate index Nino4 (El Niño Southern Oscillation). ...
Northwest Algeria has experienced fluctuations in rainfall between the two decades 1940s and 1990s from positive to negative anomalies, which reflected a significant decline in rainfall during the mid-1970s. Therefore, further analyzing rainfall in this region is required for improving the strategies on water resource management. In this study, we complement previous studies by dealing with sub basins that were not previously addressed in Tafna basin (our study area located in Northwest Algeria), and by including additional statistical methods (Kruskal–Wallis test, Jonckheere-Terpstra test, and the Friedman test) that were not earlier reported on the large scale (Northwest Algeria). In order to analyse the homogeneity, trends, and stationarity in rainfall time series for nine rainfall stations over the period 1979–2011, we have used several statistical tests. The results showed an increasing trend for annual rainfall after the break detected in 2007 for Djbel Chouachi, Ouled Mimoun, Sidi Benkhala stations using Hubert, Pettitt, and Buishand tests. The Lee and Heghinian test has detected a break at the same year in 2007 for all stations except Sebdou, Beni Bahdel, and Hennaya stations, which have a break date in 1980. We have confirmed this increasing trend for rainfall with other trend detection methods such as Mann Kendall and Sen’s method that highlighted an upward trend for all the stations in the autumn season, which is mainly due to an increase in rainfall in September and October. On a monthly scale, the date of rupture is different from one station to another because the time series are not homogeneous. In addition, we have applied three tests enabling further results: (i) the Jonckheere-Terpstra test has detected an upward trend for two stations (Khemis and Hennaya), (ii) Friedman test has indicated the difference between the mean rank again with Khemis and Hennaya stations and the Merbeh station, (iii) according to the Kruskal-Wallis test, there have been no variance detected between all the rainfall stations. The increasing trend in rainfall may lead to a rise in stream flow and enhance potential floods risks in low-lying regions of the study area.
... These mountain ranges play a crucial role in shaping the region's climate diversity, contributing to the variability observed in precipitation patterns (Meddi and Meddi, 2009;Ghenim and Megnounif, 2016). The climate of northern Algeria varies across different regions. ...
This paper examines the characteristics associated with the spatiotemporal evolution of extreme precipitation, assesses its recurrence frequency, and predicts future return levels over northern Algeria. The study employs extreme precipitation indices in conjunction with the application of extreme value theory to a rainfall dataset spanning from 1982 to 2022. The study focused on modeling the index that demonstrated the highest percentage of significant positive trends at the α = 0.05 significance level. This was accomplished through the utilization of the Mann-Kendall test and the generalized extreme value distribution. Subsequently, the model was validated using the Kolmogorov-Smirnov fit test. The results revealed that the northeastern region of the study area experienced a more pronounced increase in rainfall intensity compared to the southern and western regions. Significant trends in precipitation intensity were observed over time. Notably, the index of days with rainfall exceeding 20 mm demonstrated the highest percentage of positive trends, with 88% of meteorological stations exhibiting an upward trend. Furthermore, a strong correlation was identified between the index of days with rainfall exceeding 20 mm and the very wet days index, particularly in the high plateaus and western region. This finding supports the hypothesis that extreme rainfall patterns are becoming more frequent in the region.
... Overall, the RCA4-CNRM-CM5 and RCA4-MPI-ESM-LR models reproduce correctly the seasonality of temperature over the Chiffa basin during the reference period, which was confirmed by several previous studies that found that temperature does not have a significant spatial variability, and climate models are generally able to reproduce it correctly over the study area and over Algeria (Meddi and Meddi, 2009;Taibi et al., 2013;Bessaklia et al., 2018;Drouiche et al., 2019;Taibi et al., 2019). ...
Introduction: This study aims to assess the efficacy of Quantile mapping (QM) and Delta change (DC) bias correction methods to improve hydrological simulations of the Chiffa basin in northern Algeria. The main issue addressed is the need for corrected climate data to provide reliable hydrological projections in semi-arid climates. Methods: Hydrological simulations were conducted using the GR2M conceptual rainfall-runoff model, recognized for its robustness in Mediterranean climates. This model was coupled with precipitation simulations from the Rossby Centre regional atmospheric model RCA4 of the Coordinated Regional Climate Downscaling Experiment (Cordex-Africa) forced by two global circulation models (MPI-ESM-LR and CRNM-CM5). Hydrological projections were produced for the future period 20702099 under RCP 4.5 and RCP 8.5 scenarios, comparing raw and bias-corrected data. Results and discussion: The findings indicate that raw precipitation data are inadequate for reflecting future rainfall trends and simulating future flows. Bias correction methods significantly improved the models performance, with the coefficient of determination (R 2) increasing from 0.440.53 to 0.830.97. Additionally, regional climate models project a 5 to 8% decrease in annual flows by the end of the 21 st century under RCP 4.5 and RCP 8.5 scenarios. These results highlight the importance of bias correction methods for hydrological impact studies, and we recommend implementing specific adaptation measures, such as improved irrigation efficiency, development of water storage infrastructure, and adoption of drought-resistant agricultural practices. Future research should focus on employing multivariate bias correction methods, utilizing higher-resolution climate data (≤10 km), and implementing ensemble modeling approaches to better characterize uncertainties.
... Two future scenarios have been proposed and considered: (i) deterioration of groundwater quality due to climate change (resulting in a decrease in recharge) (Meddi H & Meddi M 2009), anthropogenic pollution, and overexploitation situations and (ii) implementation of artificial recharge method and modern irrigation systems to improve the groundwater quality status. The two scenarios are projected to span approximately the next 10 (up to 2030). ...
The primary goal of this study is to predict the current and future water quality index for irrigation (WQII) of the western Mitidja alluvial aquifer in northern Algeria. The modified WQII was used to evaluate groundwater suitability for irrigation through geographic information system (GIS) techniques. Additionally, a long short-term memory (LSTM) model was employed to calculate the WQII and map future groundwater quality, considering factors like overexploitation, anthropogenic pollution, and climate change. Two scenarios were analyzed for the year 2030. Results from applying the modified WQII model to 2020 data showed that about 83% of the study area has medium to high groundwater suitability for irrigation. The LSTM model exhibited strong predictive accuracy with determination coefficients (R²) of 0.992 and 0.987, and root mean square error (RMSE) values of 0.061 and 0.084 for the training and testing phases, respectively. For the first 2030 scenario, the area with low and medium groundwater suitability is expected to increase by 4% and 7% compared to the 2020 map. Conversely, under the second scenario, groundwater quality is predicted to improve, with a decrease of 14% and 11% in the low and medium suitability areas. The combination of the modified WQII and LSTM model proves to be an effective tool for estimating and predicting water quality indices in similar regions globally, offering valuable insights for water resource management and decision-making processes.
... The SPI, developed by [10], is designed to quantify precipitation deficits and enhance the detection and monitoring of droughts over a specified period. It is a straightforward, powerful, and user-friendly index based solely on precipitation data [11,12,13]. Furthermore, the SPI is equally effective for analyzing both wet and dry periods. ...
In recent decades, drought has become a significant phenomenon attributed to climate change variability. Its long-term repercussions can lead to substantial agricultural, hydrological, social, and economic consequences. This study uses the Standardized Precipitation Index (SPI) to assess drought in Morocco’s SoussMassa watershed, revealing a significant decline in annual precipitation and highlighting the region’s increased drought susceptibility. Specifically, we analyzed data from five weather stations: Amaghouz (1978-2016), Amsoul (1979-2016), Immerguen (1971-2016), Lamded (1982-2016), and Taroudant (1967-2016) using statistical methods recommended by the World Meteorological Organization (WMO) for annual rainfall records. Additionally, we applied the SPI over a 12-month period to identify dry and wet years. Our analysis reveals alternating dry and wet phases, characterized by an overall decline in annual precipitation.
... Au cours du XX e siècle, l'Algérie du Nord a connu une alternance de périodes sèches et humides. La tendance à la hausse de la pluviométrie apparaît aux années 1930 et 1950, puis en revanche la baisse du régime pluvial s'est marquée au début des années 1940 et au milieu des années 1970 (Meddi et Meddi, 2009). ...
Cet article met en évidence la répartition saisonnière des précipitations dans le bassin versant de Beni-Bahdel, et son impact sur les écoulements de surface et les transports solides en suspension. Pour ce faire, nous avons exploité les données météorologiques, les débits liquides et les concentrations de matières en suspension fournies par l’Agence Nationale des Ressources Hydriques (ANRH) sur une période de 46 ans (1972-2018). En considérant uniquement les écoulements de surface, nous avons établi les relations directes entre les précipitations et les débits liquides et entre les précipitations et les transports solides pour mettre en évidence l’impact saisonnier des précipitations sur l’érosion et les ruissellements de surface. Les résultats obtenus dans ce travail montrent que les pluies automnales et estivales provoquent directement l’érosion des versants induisant des concentrations en MES importantes à l’exutoire du bassin versant. En hiver et au printemps, elles contribuent aux écoulements de surface tout en apportant des flux d’eau significatifs au barrage. Les calculs basés sur une modélisation linéaire montrent qu’en moyenne 1 mm de pluie génère 0,031 Hm3 d’écoulement à l’exutoire du bassin et 14 x 103 tonnes de transports solides en automne, alors qu’au printemps, il provoque 0,063 Hm3 d’écoulement et 1,64 x 103 tonnes de matières en suspension.
... Algeria is one of the countries, which has experienced several drought years, with high variability in annual rainfall [HABIBI et al. 2018] with a reduction of 10% since the end of the 1970s [SAHNOUNE 2013] this may affect the water mobilized in dams and groundwater. Particularly affected is the western north region [MEDDI, HUBERT 2003;MEDDI, MEDDI 2009], where experienced deficits in rainfall from 12% to 20% [MEDJERAB, HENIA 2005]. This region suffered by drought years [MEDDI et al. 2013] with the return of rising in rainfall between 2001. ...
The drought ranked first in terms the natural hazard characteristics and impacts followed by tropical cyclones, regional floods, earthquakes, and volcanoes. Drought monitoring is an important aspect of drought risk management and the assessment of drought is usually done through using various drought indices. The western region in Algeria is the most affected by the drought since the middle of the 70s.The current research focuses on the analysis and comparison of four meteorological drought indices (standardized precipitation index – SPI, percent of normal index – PN, decile index – DI, and rainfall anomaly index – RAI) in the Tafna basin for different time scales (annual, seasonal, and monthly) during 1979–2011. The results showed that the SPI and DI have similar frequencies for dry and wet categories. The RAI and PN were able to detect more drought categories. Meanwhile, all indices have strong positive correlations between each other, especially with Spearman correlation tests (0.99; 1.0), the meteorological drought indices almost showed consistent and similar results in the study area. It was determined in 1982 as the driest year and 2008 as the wettest year in the period of the study. The analysis of the trend was based on the test of Mann– Kendall (MK), a positive trend of the indices were detected on a monthly scale, this increasing of indices trend represent the increasing of the wet categories which explains the increasing trend of the rainfall in the last 2000s. These results overview of the understanding of drought trends in the region is crucial for making strategies and assist in decision making for water resources management and reducing vulnerability to drought.
... According to Meddi and Meddi (2009), northwestern Algeria has witnessed, over the past few decades, a significant rainfall decrease ranging from 20 to 30%. Indeed, actually, Algeria ought to meet significant challenges in order to guarantee the availability and quality of its water resources in the face of numerous growing pressures. ...
The present study aims to assess the impact of human activities on the water quality of the Hammam Boughrara dam. It also highlights the crucial importance of sustainable management of water resources in the face of persistent challenges related to various forms of pollution. The study is based on an exhaustive database covering a period spread over 16 years, with monthly measurements of organic pollution indicator parameters, namely BOD5, COD, NO2-,NO3-, PO43-, NH4+, Organic Matter (OM), TDS, Dissolved Oxygen (DO) and pH. The box plots showed an asymmetric distribution of almost all the parameters, with significant seasonal variations in the interquartile (IQR) range. The IQR ranges for NH4+ extends from 0.575 mg/l (summer) to 4.445 mg/l (spring), and for PO43- from 1.3075 mg/l (autumn) to 1.8625 mg/l (spring). This led to the use of the Spearman method for the analysis of correlations between different parameters. The seasonal study of the five categories of water quality, according to the Organic Pollution Index (OPI), revealed considerable organic pollution. At the 1% significance level, the seasonal correlation between OPI and NH4+ varies between -0.71 and -0.85, while that with PO43- fluctuates between -0.69 and -0.86. During the period analyzed, the COD/BOD Ratio (CBR) reveals two dominant categories with seasonal variations, i.e. the Moderately Biodegradable Effluents (MBE), with 96 cases, reaching 29 in autumn and 20 in spring. The Difficult to Biodegrade or Non-Biodegradable Effluents (DBE or NBE) category records 94 cases, with a maximum frequency of 26 in winter and minimum of 21 in autumn. These results therefore show the persistence of organic pollution, which had an impact on water quality over the four seasons and throughout the period studied. The results indicate persistent organic pollution affecting water quality. Therefore, prompt actions and sustainable strategies are deemed necessary to mitigate these harmful impacts and to ensure the sustainability of the water resource.
... The drought recorded during the past four years has had no equivalent, neither in duration nor in intensity over all the northern regions of Algeria. The study of drought persistence, using Markov chains, showed that, to have a non-dry year after a dry year, the probability is greater in the centre of the country than in the west (Meddi & Meddi, 2009 Otherwise, the problem also arises at the distance and spacing of supply sources, in particular with the wave of drought that is hitting northern Algeria. This led us to study the evolution of the remoteness of the sources of water supply in Algiers with a view to remediating the water crisis in this city in full growth. ...
Of all the kinds of relationship, the one that links man with water is considered as profound and serious in geographical surveys. Yet in the past, the greatest threat to agriculture was a major problem, the attention of people is now captured by water in cities. The increasing need of water in Algiers is due to the growth of population and urbanism. On the other hand, there is a rise in water needs per capita. This problem didn't arise during the last decades, but today the situation is no longer the same. It's a considerable challenge for the capital Algiers, especially for the next generations. Using a geo-history method, which consists in studying the evolution of hinterland water space in time, we will direct our research towards the exposure of the influences exerted by the increase of water needs in the zone of study. The finality of the work is to identify the water resources around the Algiers City and that arises from the spacing of evolution hinterland water. We will obtain valuable information about the extension, the distance of the hinterland water supplier from the city of Algiers. The expected result of this work is to determine the hinterland which can be counted on to supply the city of Algiers with drinking water in the medium and long term. Finally, we can think of hydraulic planning and development based on the principles of sustainable development. This with the aim of proposing solutions to current problems and ensuring the needs of future generations.
... 67 Algeria is a country located in North Africa that faces several significant chal-68 lenges. Among these challenges, we can cite drought, particularly during the 1940s 69 and 1970s [5][6][7][8][9][10][11][12][13]. Drivers such as rapid population growth, urbanization, and 70 climate change are significant factors that have profoundly impacted the region's 71 economic and environmental stability. ...
Due to rapid population growth over time, the importance of freshwater is increasing, and the availability of this vital resource is becoming progressively more challenging. Consequently, the exploitation of untapped water sources becomes a necessity. With industrial development, groundwater is increasingly exposed to various contaminants by infiltrating polluted discharges. Water resources in Algeria, especially in the Cheliff and Mitidja plains, are limited, vulnerable, and unevenly distributed spatially. This precarious situation inevitably calls for new measures to be taken to utilize these resources sustainably. Natural factors, such as drought or geological constraints, affect the supply and distribution of drinking water. Therefore, it is imperative to quantify and analyze the quantity and quality of water supplies, and to devise methods for managing this resource to ensure its long-term viability. The water quality in these regions has significantly deteriorated in recent years due to unregulated urban discharges, intensive use of chemical fertilizers, and poorly managed farms. These factors alter the chemical composition of water, rendering it unsuitable for intended purposes. This chapter offers a scientific overview of the current groundwater status in the Cheliff and Mitidja regions, focusing on both qualitative and quantitative aspects.
... Between 1980 and 1990, the region registered some of the most persistent drought seasons while the areas received less than 50% rainfall, especially in the central and western Algerian regions and 30% in the case of eastern Algeria (Berhail and Katipoğlu 2023). Various investigations (Meddi and Hubert 2003;Bekkoussa et al. 2008;Meddi and Meddi 2009;Ghenim et al. 2010;Nouaceur et al. 2013;Belarbi et al. 2017;Achite et al. 2017;Habibi et al. 2018;Djellouli et al. 2019;Hallouz et al. 2020;Mellak and Souag-Gamane 2020;Berhail et al. 2021;Derdous et al. 2021) have been conducted to study this phenomenon, find out the rationale, and determine the drought levels in this region. Furthermore, Merabti et al. (2018) employed the SPI and RDI scales to assess the drought variations in the northeastern part of Algeria for the period spanning between 1979 and 2014. ...
The current research intends to compare the agreement level between the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI), the former’s variant, at different timescales such as 1, 3, 6, 9, 12, and 24 months. This data was compiled from the Mekerra basin with the help of time series of rainfall and temperature data for 42 years from 1970 to 2011. The authors used Cohen’s kappa statistics and the Bland–Altman method to determine the test of agreement between SPI and SPEI. Furthermore, the innovative trend analysis (ITA) method was also employed to analyze the severe and extreme dry trends. The outcomes achieved from the Cohen’s kappa statistic revealed the presence of a significant level of agreement between the SPI and SPEI values across the timescales. Furthermore, the researchers observed a positive linear correlation (r > 0.75, p < 0.0001) between the ratings under study. The existence of a small mean difference between the Bland and Altman analyses confirmed the level of agreement between the analytical tools under consideration. In addition to these, the outcomes also infer that in case of the unavailability of the temperature data to conduct the SPEI. Therefore, it is acceptable to use the SPI as the current study found the presence of an acceptable degree of agreement between these two scales in the study location. The present study suggests utilizing various types of drought indices to evaluate the drought performance in a specific location or geographical area to make knowledge-driven decisions.
... According to Meddi and Meddi (2009), northwestern Algeria has witnessed, over the past few decades, a significant rainfall decrease ranging from 20 to 30%. Indeed, actually, Algeria ought to meet significant challenges in order to guarantee the availability and quality of its water resources in the face of numerous growing pressures. ...
The present study aims to assess the impact of human activities on the water quality of Hammam Boughrara Dam, while highlighting the importance of seasonal variations of the organic pollution indicator parameters. The COD/BOD 5 Ratio (CBR) values, over the period mentioned above, revealed the dominance of two categories, namely Moderately Biodegradable Effluent (MBE) and Difficult to Biodegrade Effluents (DBE) or Non-Biodegradable Effluents (NBE), with significant seasonal variations. The MBE category showed a maximum frequency in autumn (29 occurrences) and a minimum frequency in spring (20 occurrences), while the DBE or NBE category had a maximum frequency of 26 during winter and a minimum frequency of 21 during the autumn season. The analysis of Organic Pollution Index ( OPI) revealed that the water of the dam under study is strongly impacted by organic pollution, with significant seasonal variations. This is confirmed by the predominance of the Organic Pollution (OP) category, with a maximum frequency in autumn and summer seasons (25 occurrences) and minimum in spring (21 occurrences), as well as by the Very Strong Organic Pollution (VSOP) category, with a maximum frequency in winter (23 occurrences) and minimum in summer (11 occurrences). The box-plot graphs showed positive skew, while others exhibited a negative one, with significant seasonal variations in the InterQuartile Range (IQR). It should also be mentioned that the correlation of the Organic Pollution Index (OPI) with the concentrations of NH₄⁺ and PO₄³⁻ ions is higher than that of the OPI with BOD 5 and NO₂⁻. However, it must be recognized that the correlation between the OPI and BOD 5 as well as NO₂⁻ remains significant at 1% threshold level. Moreover, the correlation coefficients showed significant seasonal variations. It is worth noting that the OPI showed a positive correlation with the dam’s water volume, during all four seasons, with correlation coefficients varying significantly for each season. On the other hand, the OPI exhibited negative correlation with COD, TDS and concentrations in some seasons. In addition, positive correlations were observed between the concentrations of and ions, as well as between the concentrations of and ions, throughout the four seasons.
... Algeria, like other semiarid countries, has been affected by severe droughts since the mid-1970s (Tardy and Probst 1992;Laborde 1993;Ait Mouhoub 1998;Khaldi 2005;Ed-Daoudi 2014). This water stress, which lasted until the early 2000s, intensified from east to west of the country (Matari et al.1999;Meddi and Meddi 2009). This climate variability has had a significant impact on the hydrological cycle and water resources; indeed, the research established in this direction has shown that the basins of the northwest were much more affected and that this disruption of hydro-climatic behavior led to a reduction in runoff of around 70% (Meddi and Hubert 2003;Ghenim et al. 2010). ...
Rainfall-flow modeling remains necessary, even essential, to understand the dynamics of a watershed and to solve problems related to the disruption of hydrological regimes. It has been proven effective by providing solutions to many water-related problems, such as sizing and management of structures, and flood forecasting. Global hydrological models can simulate the transformation of rainfall data into flows on natural basins for many practical applications in the field of water resource management. Our study aims to evaluate the reliability of one of these models, that of Rural Engineering 'GR' at three time steps: annual (GR1A), monthly (GR2M), and daily (GR4J), which will be applied to the Beni Bahdel watershed with an area of 1040 km², one of the sub-basins of Northwestern Algeria. The input parameters are precipitation and potential evapotranspiration (PET), and the output parameters are flows. The results obtained, both in calibration and validations, are encouraging, where the evaluation criteria taken into consideration, namely the Nash criterion and the correlation coefficient, exceeded 70% and 0.80 respectively. The study could be a decision-making tool for the simulation of flows, and be very useful for future hydraulic developments in the study area.
... Drought is one of the primary random natural disasters in terms of cost and impact worldwide (Hewitt, 1997;Wilhite, 2000). Like the rest of the world, Algeria was affected by a severe and persistent climatic drought characterized by a significant lack of rainfall (Meddi & Hubert, 2003;Meddi & Meddi, 2009;Ghenim et al., 2010). This drought has particularly affected the north-western part of Algeria, where annual rainfall is less than 100 mm (Khaldi, 2005;Medejerab & Henia, 2011). ...
Drought is a consequence of climate change in many parts of the world. Furthermore, it became more complicated in the areas of rain-fed agriculture, so this study came to assess the meteorological drought temporally and spatially and to count the wet and dry years that passed over the Ain Defla region in northwestern Algeria. as it is an agricultural region most of its production depends on rain. It was negatively affected by the drought that lasted for many years. Thirteen stations within the study area were selected to obtain precipitation data to calculate the Standardized Precipitation Index (SPI) on an annual scale for 38 years from 1981 to 2019. Using Geographic Information Systems (GIS) and following the Kriging approach, digital maps have been created to determine drought distribution. The results showed that the region was exposed to droughts of varying severity and impact towards the east over the years (81-83-89-93-94-00), interspersed with wet periods that prevailed during the years (84-86-96-11-13-18). Two types of arid regions were counted within the region, the first in the west of Ain Defla, less arid than the second in the east. So in the future, agriculture in the region should prioritize crops less sensitive to drought.
... For instance, groundwater quantity is caused by modifications of the rainfall regime, which have worsened over the years due to climate change (Sappa et al., 2018;Lentini, 2021). In the regions of northern Algeria, several authors have proven a significant drop in precipitation from the mid-1970s especially in the west regions where the rainfall deficit varies between 16% and 43% (Meddi, H. & Meddi, M., 2009;Bouguera, 2020;Gherissi et al., 2021). ...
The aim of this study is to assess the main climatic characteristics and their impact on the hydrological regime at the watershed and the hydrodynamic functioning of the aquifer in the Eastern Mitidja plain (Algeria, 2,382 millions km2). In detail, specific objectives are to determine the recharge mode of the aquifer, to propose solutions for the groundwater overexploitation and to remedy the seawater problem in its northeastern part. The application of three statistical methods (Pettitt’s, Buishand’s U statistic and, Lee and Heghinian’s tests) and two drought indices (SPI and Ipmc) allowed identifying the wet and dry periods for the time interval 1906-2018. In addition, the piezometric maps analysis for the years 1973, 1981, 2015 and 2020 was carried out to investigate the hydrodynamic behavior of the study area and to determine the effect of the hydrological regime on the hydrogeological functioning of the aquifer. Results obtained by the application of the three statistical methods and two drought indices indicate two distinct periods. The first period is wet and it extends from 1906 to 1973, while the second period is dry and it goes from 1974 to 2018. It is characterised by a rainfall deficit between 15% and 19% compared to the previous period (1906-1973). Furthermore, a significant drawdown in the piezometric levels is observed from 1973 to 2020, varying between 10 and 80 m, that indicates a negative trend of piezometric levels. This drawdown coincides with the rainfall deficit noticed during the period 1973-2018. Also, seawater intrusion was observed in the northeastern part of the plain. To enhance groundwater management, an effective remediation strategy is to use an artificial recharge technique from the existing wastewater treatment plants in the region, complemented by stopping the pumping of wells in coastal zones that are affected by seawater intrusion supplemented by a hydro-chemical monitoring of the groundwater.
... The area is characterized by a Mediterranean climate, with annual average values of ~530 mm for precipitation, 18.5 °C for temperature, 348 mm for evaporation and 80 mm for runoff (Meddi and Meddi 2009). It also features erosion-sensitive soil that is dominated by silty-clayey minerals. ...
Algerian soil is exposed to intense soil erosion due to several factors, mainly natural and human. In the present work, the assessment of soil erosion–deposition processes in a forest area using the fallout radionuclide cesium-137 is proposed. The Cs-137 technique, which is used for investigating rates and patterns of soil erosion, has been successfully applied in a wide range of environments. This radionuclide is known to strongly adhere to soil particles and therefore can be used as a tracer in soil movement investigations. Three different sites were selected for this study, namely a forest site, a burnt forest site and an agricultural one, all located in a Mediterranean area near Ténès (North-Central Algeria). The results showed that the agricultural site is characterized by the highest decrease in cesium-137 activity and is then the most exposed to soil erosion. Cesium-137 activity in the reference site is about 2842 Bq·m−2. It varies from 2288 to 4464 Bq·m−2 in the burnt site, from 1951 to 3440 Bq·m−2 in the forest site, and from 1359 to 2448 Bq·m−2 in the agricultural site. Results showed that the erosion rate reaches a maximum value of 39 t·ha−1·yr−1 in the agricultural site, 9.92 t·ha−1·yr−1 in the forest site, and 5.63 t·ha-1·yr−1 in the burnt site, whereas the highest deposition rate is about ~16 t·ha−1·yr−1 both in the burnt site and in the forest site. Such results contribute to a better understanding of land degradation processes and are of great assistance to rural engineers and local authorities in charge of the implementation of soil conservation measures, especially in such a semi-arid environment where combating desertification is a crucial issue.
... This finding is also reinforced by a comparison with previous studies on a regional scale, notably with some studies conducted in neighboring countries. In Algeria, a previous study showed a decrease in the annual rainfall exceeding 36% in the Mascara region and in the extreme west around 1980 (Meddi and Meddi, 2009). Research studies conducted in the north-western part of Algeria demonstrated that since the 1980s, aquifer output has decreased by more than 50% (Khaldi, 2005;Nekkache and Megnounif, 2013). ...
This study aims to analyze rainfall data series of four hydrometric stations in a mountainous context in Morocco, over the period 1970–2017. Periods of disruption were identified through statistical approaches based on rupture detection: the Pettitt test, the Bayesian procedure of Lee and Heghinian, and the Buishand test. The results show that the studied series are characterized by several breaks which indicate a variation in the overall trend of the rainfall regime during 1980, 1995, 2000, and around 2010. In addition, a diagnostic of dry and wet years is carried out by applying the Standardized Precipitation Index (SPI); a prolonged period of drought was observed from 1980 to 2010, with the exception of several short-term rainy events, such as in 1994–1996 and the early 2000s. The variability of spring discharge indicates an evolution consistent with that of rainfall; the largest decrease in flow rates was recorded during the period from 1980 to 1993. In addition, periods of abrupt increases were identified, with a maximum recorded in 1994–1996. The phase opposition showed a marked consistency between the North Atlantic Oscillation (NAO), the SPI, and the variability of spring discharge, which provides an overview of the influence of atmospheric circulation on the evolution of precipitation and, consequently, on the availability of water resources in the area.
... En fait, la pénurie en eau dans ce bassin n'est pas récente et était toujours liée aux précipitations. Cette liaison entre les ressources en eau et les précipitations a suscité plusieurs études scientifiques, particulièrement, dans les zones arides et semi-arides (Abdou et al., 2008 ;Amraoui et al., 2004 ;Meddi H et Meddi M, 2009 ;Khomsi, 2014). Au Maroc, la sécheresse climatique a touché l'ensemble du Royaume avec des conséquences dramatiques sur les ressources en eau et les systèmes humains et naturels (GIEC, 2007) dans plusieurs régions, notamment les plaines à forte productivité agricole. ...
L’objectif de la présente étude est de déterminer l’influence de la lithologie,
comme variable géo-écologique, sur la répartition des principales espèces arborées et
arbustives du Moyen Atlas Central, ainsi que sur les caractéristiques dendrométriques des
arbres. La superposition de la carte de végétation et la carte géologique a permis de
déterminer la répartition des espèces en fonction de la nature lithologique des terrains.
Cette relation est testée par la comparaison des caractéristiques de deux peuplements de
cèdre de l’Atlas qui se développent sur deux facies lithologiques différents. Les facteurs
testés sont la densité, la croissance radiale des arbres, la surface terrière et la croissance
en volume. Afin de mieux comprendre cet impact, une étude de caractérisation des sols des
deux sites a été effectuée, et les potentiels de séquestration du carbone et de minéralisation
de l’azote ont été déterminés. Les résultats obtenus montrent que la répartition spatiale de
la végétation ainsi que sa dynamique de croissance sont largement influencées par le
facteur lithologique.
... En fait, la pénurie en eau dans ce bassin n'est pas récente et était toujours liée aux précipitations. Cette liaison entre les ressources en eau et les précipitations a suscité plusieurs études scientifiques, particulièrement, dans les zones arides et semi-arides (Abdou et al., 2008 ;Amraoui et al., 2004 ;Meddi H et Meddi M, 2009 ;Khomsi, 2014). Au Maroc, la sécheresse climatique a touché l'ensemble du Royaume avec des conséquences dramatiques sur les ressources en eau et les systèmes humains et naturels (GIEC, 2007) dans plusieurs régions, notamment les plaines à forte productivité agricole. ...
CHANGEMENT CLIMATIQUE, POTENTIALITES TERRITORIALES ET JUSTICE ENVIRONNEMENTALE
Coordination: Hanchane Mohamed et El Khazzan Bouchta
... Algeria, which is one of the countries on the southern shore of the Mediterranean, has been affected by the consequences of this decrease in rainfall in several northern regions, particularly the northwestern zone (Meddi and Meddi 2009;Meddi and Toumi 2013;Ghenim and Megnounif 2013;Taibi et al. 2015;Elouissi et al. 2017;Drouiche et al. 2019;Khedimallah et al. 2020). ...
Wadi Isser watershed (4149 km2), located in the North of Algeria, has experienced a significant rainfall variability during the last four decades. In order to characterize this variability and determine its spatial extension, by means of the analysis of the rainfall data measured in twenty-seven (27) stations, the following study was conducted. The analysis of the long rainfall series of the reference stations of Bni Slimane (1920–2014) and Djebahia (1923–2014) through the application of three statistical tests (Pettitt, Buishand and Lee and Heghinian) revealed an episode of low rainfall from 1973 to 2001 for the Djebahia station and from 1975 to 2001 for the Bni Slimane station. This period was characterized by a decrease in annual rainfall varying between 14 and 43%, followed by a rainy phase in the watershed with an increase in annual rainfall (35.8%) at the Khebouzia station. The analysis of the kriged maps, developed by geostatistical modeling of the spatial structure of precipitation (1975–2014), supported and corroborated the results of the statistical tests. Indeed, the spatial interpolation based on decadal averages of rainfall from 1975 to 2014 illustrates a well-contrasted spatial variability for the four decades. The northern part of the watershed is characterized by a higher rainfall than the central and southern parts of the watershed. In the light of the results obtained by applying the two approaches mentioned above, a decreasing trend in rainfall is clearly evident from the beginning of the decade 1985–1994. A double rainfall gradient is highlighted with an increase in rainfall from east to west and from north to south. At the same time, there was a surplus towards the end of the third decade and the fourth decade. A return of precipitation is thus highlighted as well as the different breaks in the series. Through this research, the statistical study and the geostatistical mapping have enabled the elaboration of a relevant tool for decision support to the managers in the field of environment and hydraulics, in a general way, and in a context of global warming. In fact, it will allow them to better understand the developments of wadis, the integrated management of water resources in order to guarantee current and future needs for drinking, industrial, and agricultural water in this semi-arid region.
... ne superficie de 21035 Km 2 . Elle est limitée au Nord par les monts du Zaccar, au Sud par les contreforts de l'Ouarsenis, à l'Ouest par le massif de Doui et à l'Est par Djebel Gountas. Elle a une pente relativement faible (15%). Elle est bordée au Nord par des cônes de déjection qui constituent la zone de transition entre la vallée et la montagne.(Meddi,H et Meddi, M, 2009).La plaine du Moyen Cheliff se situe au centre du bassin du Chellif à 200 km à l'Ouest d'Alger et 35 km à vol d'oiseau de la méditerranée. Elle est limitée au Nord par les monts de Medjadja, à l'Est par le seuil d'Oum Drou (Pontéba), au Sud par les monts de l'Ouersenis et à l'Ouest par le seuil de Boukadir. . 3.2. Carte de situation de l ...
L’objectif principal de cette thèse est de diagnostiquer le fonctionnement hydrologique du
bassin versant du Haut et Moyen Cheliff. Afin d’atteindre cet objectif, cette étude est
organisée autour de deux grands axes. Le premier axe est consacré à la variabilité hydro
pluviométrique sur la période 1972/73-2013/14 (soit 42 ans). Le bassin versant du Haut et Moyen Cheliff connait une variabilité pluviométrique marquée par une longue période sèche amorcée depuis la fin des années 1970 qui s’est amplifiée pendant les années 1980 et les années 1990. Le déficit pluviométrique évalué fluctue entre 16% et 29%. La variabilité pluviométrique se manifeste également par une baisse importante de la pluviométrie mensuelle. Les mois de la saison humide sont plus affectés, dans l’ensemble, que ceux de la saison sèche. Les mois de juin et juillet sont généralement déficitaires. L’évolution des débits dans le bassin du Haut et Moyen Cheliff a montré de fortes fluctuations de débits d’une année à une autre, ainsi qu’une abondance de l’écoulement durant la période 1973 à 1986 et une indigence de 1987 à 2005. Le deuxième axe consiste à identifier des tendances au sein de la relation pluie-débit et d’étudier ses impacts sur les ressources en eau du bassin versant du
Haut et Moyen Cheliff. L’étude de la modélisation de la relation pluie-débit en utilisant les
modèles GR1A et GR2M a montré leur performance et leur robustesse à simuler les
écoulements. Ainsi, ces deux modèles ont identifié l’existence de deux tendances opposées, la première tendance est à la baisse (diminution des débits) aux seins du comportement hydrologique de trois sous-bassins (Oued Cheliff Harraza, Oued Rouina Zeddine et Oued Cheliff Tickezal). La seconde est à la hausse (augmentation des débits) dans le comportement hydrologique du sous bassin d’Oued Ras Ouahrane. Quant au cinquième sous bassin d’Oued Sly, les tests statistiques n’ont pas pu identifier avec les modèles, une tendance dans son comportement hydrologique. Une étude comparative a été effectuée entre trois modèles globaux et conceptuels et/ou semi-distribués : GR4J, HBV Light et GARDÉNIA. Sur les trois modèles utilisés, GR4J et HBV Light, présentent de très bonnes performances à la fois en calage et en validation, Quant à GARDÉNIA, il présente des performances assez acceptables.
Mots clés : Variabilité hydro-pluviométrique, modélisation, relation pluie-débit, ressources en eau, Haut et Moyen Cheliff.
... L'Algérie fait partie des pays semi-aride et aride les plus exposés au phénomène de changement climatique. Ainsi, l'Algérie est passée depuis les 30 dernières années à un déficit hydrique sévère et persistant sur plusieurs années, issu d'un déficit pluviométrique évalué à 30% [6]. Cette sécheresse a pour conséquence de graves baisses des précipitations, des niveaux piézométriques et la chute des débits des cours d'eau [3]. ...
Résumé :
En Afrique du Nord, les changements climatiques ont été mis en évidence par la dernière période de sécheresse depuis le début des années 1970 [1]. La sécheresse affecte de nombreuses régions, comme ça été le cas dans l’Afrique où la grande sécheresse a touché 16 pays entre 1968 et 1973 (la Mauritanie, le Sénégal, le Mali, le Burkina-Faso, le Tchad, le Niger, la Libye, le Soudan). Les études sur le changement climatique montrent qu’au Maghreb le réchauffement climatique est plus important que la moyenne. Si au niveau mondial, la hausse a été évaluée à 0,74°C (0.56 °C ± 0.9°C) au 20ème siècle, elle a été située entre 1°C-2°C dans le bassin méditerranéen et la région de l'Afrique du Nord [2-3]. La sécheresse a toujours été présente dans l’histoire du Maroc, elle s’est imposée avec force ces dernières décennies en tant qu’élément structurel du climat du pays. La caractérisation de la sécheresse climatique au cours de la période 1961-2004 a montré une augmentation significative de la fréquence des sécheresses, de leur sévérité et de leur champ de couverture spatiale [4]. L’étude de la pluviométrie annuelle de la Tunisie centrale par la méthode de la variable centrée réduite a mis en évidence une certaine baisse de la pluviométrie entre 1976 et 1989[5]. Cependant en utilisant des tests statistiques, il n’a pas été montré de rupture de stationnarité dans les séries chronologiques considérées. Par contre, l’étude de la persistance temporelle des classes de pluies a montré une baisse très significative des pluies supérieures à 30 mm après 1976.
Au Liban, d’après des experts, le réchauffement climatique et le manque de pluie menace les cèdres millénaires du Liban, cèdre qui est l'arbre symbole du pays, ce cèdre arboré sur la monnaie et le drapeau libanais.
La Mauritanie est située dans l’une des six régions du monde qui seront les plus affectées par les impacts du réchauffement climatique d’après le dernier rapport du « Groupe Intergouvernemental d’Experts sur l’Evolution du Climat (GIEC) ». Par ailleurs les précipitations annuelles, et leurs variations sont de plus en plus incertaines d’après le modèle global des météorologues.
L’Algérie fait partie des pays semi-aride et aride les plus exposés au phénomène de changement climatique. Ainsi, l’Algérie est passée depuis les 30 dernières années à un déficit hydrique sévère et persistant sur plusieurs années, issu d’un déficit pluviométrique évalué à 30% [6]. Cette sécheresse a pour conséquence de graves baisses des précipitations, des niveaux piézométriques et la chute des débits des cours d'eau [3]. Elle a sévit particulièrement dans les régions steppiques et en particulier, le bassin versant des Zahrez, caractérisé par son climat semi-aride. Dans cette région la demande en eau et la sécheresse associée ont causé une diminution des ressources en eau souterraine, qui jouent un rôle important dans l’alimentation en eau potable, ainsi que l’irrigation des terres agricole [9-10].
La zone étudiée fait partie des Hauts plateaux centre de l’Algérie, caractérisée par un climat semi-aride. Elle occupe la partie centrale de l’Atlas saharien. Situé à 300 Km au Sud d’Alger, Entre 3°.4’ et 34° 90’de l’altitude Nord et 3°.21’ et 3° 70’de Longitude Est. Cette région est caractérisée par un climat semi‑aride avec une pluviosité moyenne annuelle inférieure à 300 mm, Le climat qui règne dans ce bassin est de type semi-aride méditerranéen marqué par des précipitations faibles et irrégulières, avec une moyenne annuelle qui ne dépasse guère les 300 mm, une évapotranspiration annuelle de 1382 mm et une température moyenne annuelle de 15.5°C [9]. La caractérisation de la variabilité climatique dans le bassin versant des Zahrez et son influence sur les ressources en eaux à l'aide de méthodes statistiques constituent les objectifs majeurs de cette étude. L’approche adoptée dans cette étude est basée sur la détection de ruptures au sein des séries pluviométriques dans le bassin versant des Zahrez entre 1974 et 2007, en appliquant la méthode de l'indice pluviométrique de Nicholson et des tests statistiques : la procédure de segmentation de Hubert, test de Buishand et l’ellipse de contrôle de Bois [10, 12,13 et 14].
L’ensemble des résultats montre que pendant la période 1974–2007, plus de 60 % des postes pluviométriques retenus sont caractérisés par une succession de périodes d’excédents et de déficits pluviométriques. La première période de 1974 à 1982 et la deuxième période de 1983 à 2007. L’utilisation de la méthode de l’ellipse de contrôle montre que 56% des postes pluviométriques étudiés, présentent une rupture dans les séries chronologiques des précipitations annuelles aux seuils de confiance de 90 et 95 %.
Les résultats de cette étude peuvent être utilisés comme une base pour la mise en point d’une stratégie d’exploitation rationnelle des ressources en eau, pour faire face aux impacts des changements climatiques.
... Historically, the precipitation deBcit has been registering since 1973 aAecting differently the north of Algeria (Meddi et al. 2010). The duration and the severity of this deBcit varies across north-western part of the country causing severe impacts on agricultural and socio-economic features for the strong dependence of the country's economy on rain-fed agriculture in the large fertile farmland (Meddi and Meddi 2009). For the period 1970-2013, the continuous decrease in precipitations in areas previously considered temperate climate, caused very dry environment conditions (Meddi et al. 2010;Zeroual et al. 2017) with reservoir levels dropped up to 25% of their normal level and piezometric levels decreased below 40 m for some aquifers (Demmak 2008). ...
Drought is the most frequent natural disaster in Algeria during the last century, with a severity ranging over the territory and causing enormous damages to agriculture and economy, especially in the northwest region of Algeria. The above issue motivated this study, which is aimed to analyse and predict droughts using the Standardized Precipitation Index (SPI). The analysis is based on monthly rainfall data collected during the period from 1960 to 2010 in seven plains located in the north-western Algeria. While
a drought forecast with 2 months lead-time is addressed using an artiBcial neural network (ANN) model. Based on SPI values at different time scales (3-, 6-, 9-, and 12-months), the seven plains of north-western Algeria are severely aAected by drought, conversely of the eastern part of the country, wherein drought phenomena are decreased in both duration and severity. The analysis also shows that the drought frequency changes according to the time scale. Moreover, the temporal analysis, without considering the autocorrelation eAect on change point and monotonic trends of SPI series, depicts a negative trend with asynchronous in change-point timing. However, this becomes less significant at 3 and 6 months’ time scales if time series are modelled using the corrected and unbiased trend-free-pre-whitening (TFPWcu) approach. As regards the ANN-based drought forecast in the seven plains with 2 months of lead time, the multi-layer perceptron networks architecture with Levenberg–Marquardt calibration algorithm provides satisfactory results with the adjusted coefBcient of determination (R2 adj) higher than 0.81 and the rootmean-square-error (RMSE) and the mean absolute error (MAE) less than 0.41 and 0.23, respectively.
Therefore, the proposed ANN-based drought forecast model can be conveniently adopted to establish with 2 months ahead adequate irrigation schedules in case of water stress and for optimizing agricultural production.
Recent climate change has altered global precipitation patterns, resulting in a variety of natural hazards, including flash floods, exacerbated by intensive land use and urbanization. This paper examines the spatiotemporal evolution of flooding in the Department of Algiers, focusing on two major causes: land cover and precipitation regimes and patterns. It investigates changes in land cover distribution between 1984 and 2022 using supervised classification techniques. The National Agency of Hydraulic Resources (ANRH) provided daily precipitation data from three meteorological stations over a 50-year period. Our findings show a significant increase in flood occurrences, from an average of two floods per year prior to 2006 to ten floods per year. This intensification can be attributed to the significant expansion of the urbanized area in Algiers, which increased from 18.89% in 1984 to 43.2% in 2022, with an annual growth rate of 2.92 km² to 9.68 km². Despite a decrease in annual precipitation totals and a reduction in heavy rainfall episodes due to climate change, flooding is becoming more common. Variations in rainfall patterns, particularly the intensity and duration of wet periods, play a significant role in flooding peaks, as evidenced by the extremely wet period at the end of the 2000s after a long dry spell. These findings can help civil protection and relevant authorities develop future flood risk prevention strategies.
The Rif Mountains extends 31.375 km2, is occupied in the north of Morocco, on the Mediterranean slopes, and the rainfall is relatively abundant in the western part and scarce in the eastern part, and irregular, with strong anthropic pressure. This has affected the use of forest and soil resources. This area has been subject to anthropogenic pressure which is steeped in history as an extensive agricultural- forestry-pastoral production system. This deterioration has resulted in intense erosive dynamics that can be seen in various forms, including, the areal etching, the gully and landslides. This dynamic erosion gradually and inevitably leads to soil degradation, causing serious problems in terms of loss soil and silting up of dams. To evaluate this dynamic, we have integrated of the Erosion Potential Method into a GIS & RS, for soil losses estimation allows to approach the severity of the erosive phenomenon, in order to identify as well as map the sensitive and high-risk areas of water erosion and the regions of intervention urgency in the Rif Mountains. Soil losses range from 17.254 to 0 t/ha/yr, the average rate of losses is 46 t/ha/ yr (Erosion in the plot). Potential total erosion in Rif Mountains in the order of 144.292.972 t/yr. Thus, the average amount delivered per unit area is 8.55 t/ha/yr (total of 26.825.625 t/yr).
In Algeria, prevailing climatic conditions over the past decades have had a negative impact on water resources used for irrigation. The objective of this study is to determine its effect on irrigation water requirements for citrus cultivation in the central and upper parts of the Chlef plain, a region known for its citrus production covering an area of over 64,000 hectares. Three climatological stations (Chlef, Elkhemis INRA, and Harezza Barrage) were selected for a chronology spanning 51 years (September 1968 to August 2019). In this study, we utilized the potential of agro-climatic indices such as the Thornthwaite Aridity Index (TAI), the Standardized Agricultural Precipitation Index (aSPI), the Effective Recognition Drought Index (eRDI), and wavelet analysis to characterize monthly drought at different stages of citrus development. The results show a significant increase in drought since 1980 according to the Standardized Agricultural Precipitation Index (aSPI) on scales of 1, 3, 6, and 12 months. The energy bands of three stations (1 year, 1–2 years, 2–3 years, and 3–4 years) for the months of January, February, March, September, October, November, and December show marked changes after the year 1994. Depending on the annual development stage, citrus water demand during the period 1968–2019 is strongly correlated with the new Effective Recognition Drought Index (eRDI) at various time scales. The determination coefficients are significant over a 5-month scale between the Effective Recognition Drought Index (eRDI) and irrigation water demand anomalies for the three stations (Chlef (0.73), Harezza Barrage (0.62), and Elkhemis INRA (0.62)). Considering these results, the aSPI and eRDI indices can easily be used to monitor and manage citrus irrigation in our region.
The objective of this study was to examine drought using the Streamflow Drought Index (SDI) at various time scales and its temporal evolution using monthly streamflow data from 1973 to 2009. Streamflow records were collected from a network of 14 hydrometric stations distributed throughout the study area. The Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC) were used to assess the quality of the adjustment. According to these criteria, the gamma law better suited the time scales of 3, 6, and 12 months, whereas the log-normal law was better suited to the scale of 9 months. The analysis of the Streamflow Drought Index in the three study basins (Middle and Upper Cheliff, Lower Cheliff, and the Mina) revealed that different classes of drought among 3, 6, 9, and 12-month time scales in the period of 1973 to 2009 had occurred, notably beginning in 1980. The frequency of 19 to 54% was found at all stations and in years marked by a mild drought. The moderate years had a frequency of 6 to 19%, while the severe and extreme years had a lower percentage (about 3 to 6%) in the study area. Two consecutive years of drought (D-D) were more likely in the Middle and Upper Cheliff basins (> 60%) for the 6, 9, and 12-month time scales, according to the transition of probability of first-order non-stationary Markov chain. On a three-month time scale, the transition probabilities (D-D) were greater than 50% in the Coastal basin and Lower Cheliff basin, as well as the Mina basin, and less than 50% in the Middle and Upper Cheliff basins.
The average annual precipitation values in the Cheliff-Zahrez basin range from 80 to 600 mm/an, indicating a semi-arid climate. This work revolves around a new drought exceedance probability index (DEPI), a standardized precipitation index (SPI) and effective drought index (EDI) in different time scales (3, 6, 9, 12 and 24) derived from monthly precipitation series stretching from September 1970 to August 2015. The latter aims to analyze the performance, similarities and differences between the most used drought indices such as SPI and EDI and to compare their results with those obtained using DEPI. The results indicated that the majority of selected stations tend to a decline in annual rainfall, with a dominant break in series between 1970 and 1980. The Mann–Kendall test result showed that the monthly rainfall trend had significantly decreased in the majority of studied stations. Furthermore, the SPI and EDI series showed persistent monthly drought conditions from January 1970 to March 2010 with an extreme drought peak of − 3. However, the DEPI index showed monthly drought events (< 0.5) of different classes beginning from March 1980 to December 2010. In the study area, the coefficient of determination explained a high variation (> 80%) between SPI and EDI at the time scale of 24 months. At the 9- and 12-month scale, the coefficient of determination showed a variance greater than 50% over the entire basin. On the other hand, the coefficients of determination results between SPI and EDI for the time scale of 3 to 6 months are characterized by a gradient from the northeast to southwest or from 10 to 90%. The stations of the Coastline 2 basin have revealed that the relationship between SPI and DEPI as well as EDI and DEPI is not significant, being allowed between 10 and 30% on time scales of 3, 6, 9, 12 and 24 months. The results of this work and information on the severity and persistence of droughts will be essential to enable managers to adopt an integrated and sustainable management of scarce resources and aim at minimizing agricultural production losses in the region.
The average annual precipitation values in the Cheliff-Zahrez basin range from 80 to 600 mm/an, indicating a semi-arid climate. This work revolves around a new drought exceedance probability index (DEPI), a standardized precipitation index (SPI) and effective drought index (EDI) in different time scales (3, 6, 9, 12 and 24) derived from monthly precipitation series stretching from September 1970 to August 2015. The latter aims to analyze the performance, similarities and differences between the most used drought indices such as SPI and EDI and to compare their results with those obtained using DEPI. The results indicated that the majority of selected stations tend to a decline in annual rainfall, with a dominant break in series between 1970 and 1980. The Mann–Kendall test result showed that the monthly rainfall trend had significantly decreased in the majority of studied stations. Furthermore, the SPI and EDI series showed persistent monthly drought conditions from January 1970 to March 2010 with an extreme drought peak of − 3. However, the DEPI index showed monthly drought events (< 0.5) of different classes beginning from March 1980 to December 2010. In the study area, the coefficient of determination explained a high variation (> 80%) between SPI and EDI at the time scale of 24 months. At the 9- and 12-month scale, the coefficient of determination showed a variance greater than 50% over the entire basin. On the other hand, the coefficients of determination results between SPI and EDI for the time scale of 3 to 6 months are characterized by a gradient from the northeast to southwest or from 10 to 90%. The stations of the Coastline 2 basin have revealed that the relationship between SPI and DEPI as well as EDI and DEPI is not significant, being allowed between 10 and 30% on time scales of 3, 6, 9, 12 and 24 months. The results of this work and information on the severity and persistence of droughts will be essential to enable managers to adopt an integrated and sustainable management of scarce resources and aim at minimizing agricultural production losses in the region.
When designing policies and programs, it is important to consider the limitations of adaptive capacity, of the population in certain contexts of extreme events. This may require a transformation of the systems themselves, so as to build resilience. Building resilience to climate change will require the incorporation of climate change adaptation and disaster risk reduction measures into short, medium, and long-term policies, programs, and practices. This chapter aims to propose a conceptual framework for assessing resilience in a socio-hydrological context and provide insights into how resilience can be understood and managed in Algeria in this case. The two most important extreme events are droughts and floods. Thus, the search for resilience goes through actions that act on the population’s response to the effects of climate change. Acting and responding effectively to a disaster before, during, and after depends on the right attitudes and skills of individuals acquired through education, training, and awareness-raising to the effects of climate change. Analysis of the results shows that adequate resilience in any society depends largely on water resources sector planning and water supply infrastructure. Overall, the results of this chapter suggest that several disciplines, such as eco-social management, engineering systems, and institutional management, should play a role in planning disaster resilience strategies.
In the hydrological cycle, runoff precipitation is one of the most significant and complex phenomena. In order to develop and improve predictive models, different perspectives have been presented in its modeling. Hydrological processes can be confidently modeled with the help of artificial intelligence techniques. In this study, the runoff of the Leilanchai watershed was simulated using artificial neural networks (ANNs) and M5 model tree methods and their hybrid with wavelet transform. Seventy percent of the data used in the train state and thirty percent in the test state were collected in this watershed from 2000 to 2021. In addition to daily and monthly scales, simulated and observed results were compared within each scale. Initially, the rainfall and runoff time series were divided into multiple sub-series using the wavelet transform to combat instability. The resultant subheadings were then utilized as input for an ANN and M5 model tree. The results demonstrated that hybrid models with wavelet improved the ANN model's daily accuracy by 4% and its monthly accuracy by 26%. It also improved the M5 model tree's daily and monthly accuracy by 4% and 41%. The wavelet-M5 model's accuracy does not diminish to the same degree as the wavelet-ANN (WANN) model as the forecast horizon lengthens. Consequently, the Leilanchai watershed has a relatively stable behavior pattern. Finally, hybrid models, in conjunction with the wavelet transform, improve forecast accuracy.
Simple Summary
In order to manage important transformations affecting a steppe area, it is necessary to analyze the existing pastoral system by evaluating the sustainability of its subsystems of production. For this reason, in this study, a tool for the evaluation of the sustainability of livestock production in a steppe area was used to identify the most sustainable systems among the various ways that livestock are managed and produced. The study was conducted in the region ranked first in terms of sheep production. Using a grid for evaluating the sustainability of livestock systems in steppe regions, the impact of each system on the environment (environmental, economic, and social) was examined, and the results showed that the feed system was unbalanced, with high pressure on steppe rangelands. Nevertheless, multiple ways of improving these systems emerged from the analysis, such as encouraging the production of fodder and its association with livestock on new spatial, temporal, regional, and national levels.
Abstract
In order to manage important transformations affecting a steppe area, it is necessary to analyze the existing pastoral system by evaluating the sustainability of its subsystems of production. For this reason, in this study, a tool for the evaluation of the sustainability of livestock production in the steppe area was used in order to identify the most sustainable systems. The study was conducted using a survey of 87 livestock farmers (production units) in the region ranked first in terms of sheep production. Principal component analysis (PCA) enabled us to identify two production systems: (i) the pastoral production system, characterized by the mobility of livestock and its high dependence on concentrated feed; (ii) the agropastoral system, combining fodder and livestock production, which is sedentary and semi-extensive. Using a grid for evaluating the sustainability of livestock systems in steppe regions, the impact of each system on the environment (environmental, economic, and social) was examined, and the results showed that the feed system was unbalanced, with high pressure on steppe rangelands. Nevertheless, multiple ways of improving these systems emerged from the analysis, such as encouraging the production of fodder and its association with livestock, on new spatial, temporal, regional, and national levels.
Drought is one of the most widespread and costliest disasters in the world. It is the consequence of a recurrent rainfall deficit linked to the spatio-temporal variability of climatic phenomena and aggravated by climate change. Algeria, an arid to semi-arid country, is highly vulnerable to climate change, particularly extreme phenomena, periodic droughts that are sometimes severe and persistent, which are a major constraint to its economic and social development. In this context, the objective of this work is the study of the characterization and regionalization of drought in the Upper and Middle Cheliff watershed based on rainfall data from nineteen (19) rainfall stations. The series used in this study correspond to the period of 1972-2013. To characterize the drought the analysis covered the deviation from mean index, the number of standard deviation index, the drought index as well as the standardized precipitation index SPI. The results of the drought index analysis indicate that the Upper and Middle Cheliff watershed recorded an alternation of dry and wet sequences over the whole period 1972-2013 whatever the index and the station considered, while the most persistent droughts occurred over the period 1980-2007. The driest droughts are those recorded in the years
The north western Atlas Mountains (Béchar region) act as refugia for relict populations of many species which highlights their interest as priority areas for conservation. Further work since the beginning of the last century has been difficult because of restricted access in a military area with long-standing border conflicts. This paper aims to analyse the temporal dynamics of the vegetation communities, to assess the floristic diversity of one of those isolated djebels, Djebel Antar, and to contribute to the knowledge of the conservation status of the species found. Surveys from 1925,1951 (published data) and 2017 (fieldwork) were interpreted and investigations were carried out on honey harvesting, production, and marketing in the Benzireg area to better understand and contribute to the development of beekeeping. A high proportion of endemic and very rare species was found. A tendency towards the homogenisation of the flora was detected with a decrease in plant diversity. Beekeeping is being tested as a means of enhancing biodiversity and contributing to the fight against vegetation degradation by reducing pastoral pressure. Djebel Antar retains its function as a refuge for biodiversity and may play an important role in conservation measures.
Morocco has been experiencing significant climatic disturbances in recent decades. The climate change issue arises mainly in terms of water deficits induced by the decrease in rainfall received and the increase in temperature. The objective of this study is to characterize the drought temporal and spatial distribution and severity within local agro-climatic zones of Settat Province. The study area extends over a distance of 85 km from North to South and concerns three agro-climatic zones. The Standardized Precipitation Index was used for drought analysis and characterization in the three zones for 107 years of rainfall data. Results show that numbers of normal average years are declining, dry years are increasing and humid years are declining in three zones. However, the SPI changes over time are not similar for the three zones, that is, the rainfall deficit is taking place more in the “Favorable Rain-fed” zone and to a low degree in the “Intermediate Rain-fed” but not in the ‘Less Favorable” zone.
This study investigates the effect of autocorrelation on temporal trends and step change on a monthly, seasonal and annual temperatures of six meteorological stations over the North of Algeria. Afterwards, links between the general atmospheric circulation, via six climate indices, and temperature data are examined. The trends in temperatures are analysed using six different versions of the Mann-Kendall approach while, the step changes of the time series are defined using the original Pettitt test and the modified-Pettitt. The Statistical tests have shown an increase in annual temperatures from 0.8 to 0.9°C since the 1980s in the coastal regions and the 1990s on the highlands. This warming most often exceeds 1°C on a seasonal scale, particularly in summer; however, no significant trend is observed in the winter. On a monthly scale, the increase in temperatures is marked between April and October. The analysis of the relationships between six climate indices and average temperatures has shown that the inter-annual temperature variability is most often associated with the East Atlantic oscillation for the entire study area. The winter temperatures are influenced by the Mediterranean oscillation as well as the North Atlantic oscillation. The East Atlantic oscillation is the dominant mode of circulation in spring and summer, whereas in autumn, the temperatures are strongly linked to the West Mediterranean oscillation. However, no significant correlations have been observed between temperatures and the Arctic oscillation and El Nino southern oscillation.
The aim of this work is to study the temporal evolution of the rainfall-runoff relations of four basins in northwestern Algeria: the Tafna Maritime, Isser Sikkak, downstream Mouilah and Upper Tafna basins. The adopted approach consists of analyzing hydroclimatic variables using statistical methods and testing the nonstationarity of the rainfall-runoff relation by the cross-simulation method using the GR2M model. The results of the different statistical methods applied to the series of rainfall and hydrometric variables show a decrease due to a break in stationarity detected since the mid-1970s and the beginning of the 1980s. The annual rainfall deficits reached average values of 34.6% during the period of 1941-2006 and 29.1% during the period of 1970-2010. The average annual wadi flows showed average deficits of 61.1% between 1912 and 2000 and 53.1% between 1973 and 2009. The GR2M conceptual model simulated the observed hydrographs in an acceptable manner by providing calculated runoff values in the calibration and validation periods greater or less than the observed runoff values. The application of the cross-simulation method highlighted the nonstationarity of the rainfall-runoff relations in three of the four studied basins, indicating downward trends of monthly runoff.
The present work aims to study the climate variability as well as the rainfall and temperature trends; it also tries to examine their impact on the annual runoff along with the piezometric level of aquifers in north-western Algeria. The time series that were recorded and analyzed during the period extending from 1927 to 2012 concerned four subwatersheds that belong to the central coastal basin of Oran. Some nonparametric tests (at the 5% level) were carried out; they allowed detecting significant decreasing rainfall and runoff trends and strongly increasing temperature trend, during the period between 1927 and 2012 in the four subbasins. In addition, the breakup dates were detected in 1975 and 1981 for the rainfall time series, with a decrease between 24 and 39 %; the runoff time series were detected 1974 and 1975, in with a drop between 52 % and 70 %; the temperature time series were observed in 1985 with an increase of about 5%. In addition to the agricultural and industrial activities, the rainfall decrease and temperature increase also affected the piezometric level of the aquifers in the western watershed under study. Indeed, this level diminished significantly from 1 to −130m, after the break date (tipping point) in the rainfall time series.
The Cheliff–Zahrez plains in Algeria are known for their fertility and agricultural production. The water deficit of the last decade has had a negative impact on agricultural production due to the scarcity of surface and underground supply resources. This paper sheds light on the weather, drought risk concerning crop irrigation in wheat yield cases. The methodology was the standardized precipitation index, which helps to identify a drought risk assessment model based on moderate frequency maps carried out by the geographic information system. Over the study area, 65 rainfall stations are considered, each with 41-year measurement period (1970/2010). According to the results, this basin has generally periods of humidity and drought with a tendency towards drought. The spatial distribution analyses of drought incidence in the derived Cheliff–Zahrez Basin (standardized precipitation index) and annual rainfall have shown that since 1970, the basin has experienced below-average rainfall, particularly in the central and northern regions. Various maps from 1970 to 2010 show that the basin is characterized by high spatial variability in rainfall from one station to another with the north and northeast sub-basins being much more sensitive to agricultural drought. Generally, the sub-basin in the western zone has a moderate vulnerability. The southern zone is characterized by moderate drought (less frequent in the basin). The drought hazard index map from 1970 to 2010 showed that the moderate and severe drought classes cover an area of 93.34% and 3.66%, respectively, with drought occurrence probabilities of 15 to 22.5% and 22.5 to 30%. The correlation is significant in the order of 70% to 75% between dry spells and wheat production.
This study analyzes the temporal variability of seasonal and annual rainfall in the Tafna watershed (Northwest Algeria),
using a homogeneous monthly rainfall database from 17 stations of 46 years of observation (1970-2015). Possible
trends in seasonal and annual variations in rainfall were detected using the innovative trend analysis (ITA), which identifies trends in the low, medium and high values of a series. The results obtained indicate that seasonal rainfall showed a
decreasing trend in winter and spring, while increasing trend is detected in summer and autumn. Low and high values
categories are the most affected by the decrease in winter, while for spring it is the medium and high values, which are
affected. In addition, spring showed the greatest decrease in arithmetic average and standard deviation. On the other
hand, summer and autumn, present a growing trend affecting the low and high values, while in autumn, these are the
medium and high values. Summer recorded the maximum increase in arithmetic average and standard deviation, and
may present a flooding risk in future. Annually, a decreasing trend dominate. Most stations are marked by a decrease in
their annual arithmetic means and standard deviation.
This study analyzes the temporal variability of seasonal and annual rainfall in the Tafna watershed (Northwest Algeria), using a homogeneous monthly rainfall database from 17 stations of 46 years of observation (1970-2015). Possible trends in seasonal and annual variations in rainfall were detected using the innovative trend analysis (ITA), which identifies trends in the low, medium and high values of a series. The results obtained indicate that seasonal rainfall showed a decreasing trend in winter and spring, while increasing trend is detected in summer and autumn. Low and high values categories are the most affected by the decrease in winter, while for spring it is the medium and high values, which are affected. In addition, spring showed the greatest decrease in arithmetic average and standard deviation. On the other hand, summer and autumn, present a growing trend affecting the low and high values, while in autumn, these are the medium and high values. Summer recorded the maximum increase in arithmetic average and standard deviation, and may present a flooding risk in future. Annually, a decreasing trend dominate. Most stations are marked by a decrease in their annual arithmetic means and standard deviation.
This study aims to estimate hydrological drought risk using probabilistic analysis of bivariate drought characteristics to assess both past and future drought severity and duration in three basins located in the widest karst massif of northern Algeria. The procedures entail: (1) identification of extent of meteorological drought that could trigger corresponding hydrological drought through their characteristics; (2) assessment of future risk of extreme drought according to two emission scenarios of the representative concentration pathway (RCP 4.5 and 8.5); and (3) estimation of drought return periods using bivariate frequency analysis and investigation of their future change rates under climate change. Hydrological droughts were computed by using the bias-corrected future climate projections from nine global climate models downscaled using the Rossby Centre Regional Climate model (RCA4), and GR2M hydrological model. The analysis revealed a connection between meteorological and hydrological droughts occurrences and the response time depends on the memory effect of the considered basin. We also found strong consensus between past drought events return periods, determined by bivariate frequency analysis, and those determined by climate models under RCP8.5 scenario. Finally, in regards to drought return periods (10, 50 and 100-years), the risk of extreme drought recurrence in the future has been projected to be larger than the reference period.
Algeria shares similarities with other countries of the world facing destructive floods. The need to understand changes in the intensity, frequency and severity of floods is critical for reducing significant social, economic, and environmental implications. In this study, flood indicators derived from annual maximum series and peak over threshold series were analyzed using Mann−Kendall trend analysis and linear regression analysis. Several studies in northern Algeria found decreasing trends of annual precipitation. However, precipitation could not explain most flood indicator trends found in our study. A general decreasing annual and seasonal trends of flood indicators were detected in the wadi Cheliff Basin. This result is partly due to decreasing precipitation and partly due to the construction of dams which have significantly altered flood processes. Increasing trends were found in the Mina Basin, which could be explained as the result of increases in urban area and decrease in soil moisture content before the occurrence of floods. Conversely, there was no dependency demonstrated between significant changes and spatial scales for these flood indicators. That is to say, human impacts and climate variability likely constitute the main factors causing increasing or decreasing flood trends.
An original segmentation procedure hydrometeorology series is setailed. From the beginning of this century, the results of rainfall and discharge series analysis exhibit a West African climatological evolution in successive stages. These stages, separated by jumps, come within more and more arid general tendency. The length of the sequences between the jumps are 9 to more than 19 years long. These climatological sequences, computed from various time series are concomitant and then have a regional significance.RésuméUne procédure originale de segmentation des séries hydrométéorologiques est présentée. Elle permet de mettre en évidence, aussi bien pour la pluviométrie que pour le débit de grands fleuves, une évolution climatique de l'Afrique de l'Ouest, depuis le début siècle, en séquence successives qui s'inscrivent dans une tendance générale d'aggravation de l'aridit′e. Ces séquences longues de 9 à plus de 19 ans, déterminées à partir de séries de localisation et de nature variées, sont concomittantes et ont donc une valeur régionale.
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