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The FRIEND-Water program (FWP) is the oldest and the most transverse program (i.e. Flagship Initiative) within the Hydrological Intergovernmental Program (IHP) from UNESCO. FRIEND means “Flow Regimes from International and Experimental Network Data”. The FWP is dedicated to allow large communities of hydrologists and associated disciplines to collaborate across borders on common shared data and scientific topics which are addressed through large world regions. The program has evolved in its 35 years of existence. There are 8 large regions in the world which gather tenths of hundreds of researchers, and organize events following several research topics defined according to each region priorities. The FWP is chaired by a scientific committee gathering regional coordinators and thematic experts. Each region gives its research priorities which evolve according to the projections given by the member States during the IHP council every year. The future activities of the FWP are defined by the upcoming IHP IX program and with the support of the newly created Montpellier UNESCO Category II Center ICIREWARD, acting as FWP Secretariat.

The vulnerability of the climate change in the South of the Mediterranean’s south regions varies depending on the part of their climate which is sensitive to the economy. In Tunisia, agriculture represents 16% of the workforce and 12% of GDP in 2006. In Algeria, agriculture represents 20% of the workforce and 8% of GDP in 2009. In Morocco, agriculture accounts for 40% of the workforce and 17.7% of GDP in 2006. The agriculture is directly related to the availability of water which in turn is directly related to rainfall. The drought has affected all countries of the Maghreb. It is considered the most severe in the history of these countries. The drought has forced the agricultural sector in Morocco to the limitation of annual crops which are not needed, the prohibition of any new tree planting and the ban on vegetable crops in dry years. During the years 1987, 1988, and 1989, Tunisia has experienced the most critical drought. It led to a water deficit of around 30%. For Morocco the rainfall shows a negative trend at national and regional scales, and spring rainfall has declined by over 40% since the 1960s. For Algeria, the western region has recorded a considerable reduction in rainfall. The winter rains have decreased between 40% and 70%. Contributions to dams have decreased between 30% and 50%. These changes had a negative influence on the water resource and crop yield. Many programs have been initiated since then to meet the growing demand.

The northeastern of Algeria is the rainiest region of the country, where regional catchments are often subject to devastating floods. To improve the management of water resources, there is a need to develop rainfall–runoff models. This study was conducted to propose an event‐based flood prediction model adapted to the region. Thereby, available rainfall–runoff data were used in several models to find the best one able to reproduce the flood hydrographs in three catchments. These models are based on the coupling of both production and transfer functions. For this purpose, five production functions were tested: the Soil Conservation Service–Curve Number (SCS‐CN) model, including three antecedent moisture conditions, and four modified Mishra and Singh models, incorporating antecedent moisture amounts. Three transfer functions were also tested: the Nash, Clark, and Weibull models. The tested models were all calibrated through a multi‐objective optimisation using the genetic algorithms method. It was found that the MMS models were better than the SCS‐CN method according to the performance criteria. Moreover, the proposed modified empirical equation (M4) improved runoff prediction. Furthermore, combined with the Nash model as a transfer function, the coupled model was found to be the best performing model, giving satisfactory results.

In last decades, the impact of climate change started to appear in the semi-arid regions of the Mediterranean Basin. The severity and frequency of drought events in Northwestern Algeria have affected water resources availability and agriculture. This study aims to evaluate the temporal evolution of drought events characteristics, such as drought duration, frequency and severity, of the Beni Bahdel Dam catchment, Northwestern Algeria. Drought characteristics have been derived from the Standardized precipitation index (SPI) computed for the period from 1941 to 2100 using precipitation data from observations and simulations of the regional climate model RCA4 (Rossby Centre Atmosphere model, version 4). The RCA4 model was forced by the global circulation model MPI-ESM-LR under two Representative Concentration Pathways (RCPs) scenarios. The ability of the model simulations was firstly assessed to reproduce the drought characteristics from observed data (1951–2005). Then, future changes in drought characteristics over the twenty-first century were investigated under the two scenarios (RCP4.5 and RCP8.5). Results show an amplification of drought frequencies and durations in the future under the RCP8.5 scenario.

An analysis of rainfall and hydrometric regimes was carried out over the period from 1968 to 2013 on the Cheliff basin situated in the west and the Medjerda basin in the east of Algeria. The Mann-Kendal and Pettitt tests have shown significant downward trends for rainfall, about 30% for the Cheliff basin, and 36% for the Medjerda basin, and about 61% and 43% for the flows at the level of the Cheliff and Medjerda basins, respectively. The continuous wavelet method, used during the study period, has shown three major discontinuities from the wavelet spectrum for the decades 1970s, 1980s and 1990s. Several modes of variability for different stations have been observed: annual (1 yr), interannual (2, 2-4 and 4-8 yrs), and multi-decadal (8-16) yrs. The different scales of precipitation and runoff variability seem to be clearly related to the NAO with different degrees of correlation. Continuous wavelet coherence indicates a strong correlation between the NAO climate index and precipitation with correlations ranging from 60 to 84%, and a strong relationship between the NAO and the runoff with correlations ranging from 67 to 74% for both watersheds.

Extreme hydrologic events are commonly described by several dependent characteristics, such as duration, volume and peak flow for floods. Traditionally in Algeria and North Africa, flood frequency analysis (FFA) is conducted as a univariate approach focusing separately on each single of flood characteristics. On the other hand, elsewhere, multivariate FFA studies have been conducted focusing on some FFA steps (especially modelling). The current study aims to consider complete multivariate FFA at‐site case studies in northern Algeria using 11 hydrometric stations. It is also among the first studies dealing with multivariate FFA in a complete way by considering all the required steps of the analysis (multivariate outliers detection, multivariate assumptions testing and copula fitting) and on datasets from Algeria. Multivariate stationarity, homogeneity and independence assumptions have been well verified before modelling. The Weibull distribution is mostly selected as margin distribution for the duration, volume and peak flow series. Frank, Clayton and Gumbel copulas are commonly selected to describe the dependence structure on the three flood pairs of variables. These findings should be interesting in water management and flood risk assessment in these regions. Combining these flood characteristics enables the design of more efficient hydraulic structures.

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 north-west 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 artificial 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 affected 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 effect 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 coefficient of determination ( $$ R_{\text{adj}}^{2} $$ ) higher than 0.81 and the root-mean-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.

Extreme hydrological events, such as floods and droughts, are some of the natural disasters that occur in several parts of the world. They are regarded as being the most costly natural risks in terms of the disastrous consequences in human lives and in property damages. The main objective of the present study is to estimate flood events in Cheliff watershed in giving return periods at the gauged stations, which is located in a semiarid region in the northwest of Algeria. The choice of this area is due to the significant floods observed in this watershed, which are occurring mainly from 1960 and 2006. A study is carried out to know the temporal variability and the place occupied by peak flows for both annual and monthly levels, which can finally determine the peak output of flood. We will try to understand the evolution of average and extreme flows according to rainfalls that are temporally associated with them. Frequency analysis is performed on different series of observed annual and monthly average discharges, including classical statistical tools as well as recent techniques. The obtained results show that the annual maximum approach is more appropriate in this case. This study also indicates the importance of continuous data monitoring in these stations.

The decrease in rainfall and the decrease in rainy days are also accompanied by a poor distribution of rainfall especially during the period of growth of the rain crops which usually extends from October to May. The Cheliff is under the influence of a semi-arid climate with precipitation that ranges from about 600 mm year(-1) to the northeast and 300 mm year(-1) to the west and south of the basin. The daily rainfall data used in this study concern eleven stations covering varying periods representative of different rainfall regimes in the Cheliff basin. The results obtained showed that the monthly dry sequences encountered during the rainy season decrease when the number of dry days increases, and the maximum values have been observed for the number of 1 to 7 consecutive dry days and the values were observed for a number greater than or equal to 21 consecutive dry days. It is important to say that the month of February recorded the lowest value of consecutive dry days for all stations. Also, the western stations of the study area display the largest values of the lengths of the dry sequences. Most of the stations are more correlated with the MO and AMO climatic indices than the other indices. These are the stations located west of the study area that are strongly correlated with AMO. It also appears that the total number of dry days of the stations located west of the study area is negatively correlated with SOI.

Significant changes in regional climates have been observed at the end of the twentieth century, taking place at unprecedented rates. These changes, in turn, lead to changes in global climate zones with pace and amplitude varying from one region to another. Algeria, a country characterized by climate conditions ranging from relatively wet to very dry (desert-like), has also experienced changes in its climate regions, notably in the country’s wet region, which represents about 7% of its total surface area, but is home to 75% of its population. In this study, the pace of climate zone changes as it is defined by Koppen–Geiger was analyzed for the period from 1951 to 2098 using climate data from observation and regional climate simulations over Algeria. The ability of the CORDEX-Africa regional climate models simulations to reproduce the current observed climate zones and their shifts was first assessed. Future changes over the whole of the twenty-first century were then estimated based on two Representative Concentration Pathway (RCP4.5 and RCP8.5) scenarios. Analysis of the shift rate of climate zones from 1951 to 2005 found a gradual but significant expansion of the surface area of the desert zone at an approximate rate of 650 ± 160 km2/year along with the abrupt shrinking, by approximately 30%, at a rate of 1086 ± 270 km2/year, of the warm temperate climate zone surface area. According to projections for the RCP8.5 scenario, the rate of expansion of desert climate will increase in the future (twenty-first century), particularly during the period from 2045 to 2098.

Drought and wetness events were studied in the Northeast Algeria with SPI and RDI. The study area includes a variety of climatic conditions, ranging from humid in the North, close to the Mediterranean Sea, to arid in the South, near the Sahara Desert. SPI only uses precipitation data while RDI uses a ratio between precipitation and potential evapotranspiration (PET). The latter was computed with the Thornthwaite equation, thus using temperature data only. Monthly precipitation data were obtained from 123 rainfall stations and monthly temperature data were obtained from CFSR reanalysis gridded temperature data. Both data sets cover the period 1979–80 to 2013–14. Using ordinary kriging, the gridded temperature data was interpolated to all the locations having precipitation data, thus providing to compute SPI and RDI with the same observed rainfall data for the 3-, 6- and 12-month time scales. SPI and RDI were therefore compared at station level and results and have shown that both indices revealed more sensitive to drought when applied in the semi-arid and arid zones. Differently, more wetness events were detected by RDI in the more humid locations. Comparing both indices, they show a coherent and similar behavior, however RDI shows smaller differences among climate zones and time-scales, which is an advantage relative to the SPI and is likely due to including PET in RDI.

The spatial and temporal variability of droughts were studied for the Northeast Algeria using SPI and RDI computed with monthly precipitation data from 123 rainfall stations and CFSR reanalysis monthly temperature data covering the period 1979–80 to 2013–14. The gridded temperature data was interpolated to all the locations having precipitation data, thus providing to compute SPI and RDI with the time scales of 3-, 6- and 12-month with the same observed rainfall data. Spatial and temporal patterns of droughts were obtained using Principal Component Analysis in S-Mode with Varimax rotation applied to both SPI and RDI. For all time scales of both indices, two principal components were retained identifying two sub-regions that are similar and coherent for all SPI and RDI time scales. Both components explained more than 70% and 74% of drought spatial variability of SPI and RDI, respectively. The identified sub-regions are similar and coherent for all SPI and RDI time scales. The Modified Mann-Kendall test was used to assess trends of the RPC scores, which have shown non-significant trends for decreasing drought occurrence and severity in both identified drought sub-regions and all time scales. Both indices have shown a coherent and similar behavior, however with RDI likely showing to identify more severe and moderate droughts in the southern and more arid sub-region which may be due to its ability to consider influences of global warming. Results for RDI are quite uniform relative to time scales and show smaller differences among the various climates when compared with SPI. Further assessments covering the NW and NE of Algeria using longer time series should be performed to better understand the behavior of both indices.

Le bassin versant de l'oued Mina, l'un des plus grands sous bassins du Cheliff (Nord-Ouest algerien), est soumis a une forte erosion hydrique, les sediments erodes et transportes par l'oued se deposent a l'aval dans le barrage de Sidi M'Hamed Ben Aouda.Les donnees acquises durant les campagnes de prelevements de 1971 a 2002 aux stations hydrometriques, hauteurs d'eau, concentrations en matieres en suspension_(MES) et debits solides, utilisees pour la quantification du transport solide, ont ete analysees pour decrire les cycles saisonniers et la variabilite interannuelle.L'analyse des ecoulements, a la station d'oued El Abtal, montre que les debits varient de 40,7 m3 .s-1 , en 1974, a 0,48 m3 .s-1 en 1997, soit une variabilite superieure a 95 %.Le taux d'abrasion du bassin de l'oued Mina, pendant la periode d'etude, a ete evalue a 211 t.km2 .an-1 , cette valeur reste relativement faible par rapport a celles trouvees pour d'autres regions a regime hydrologique similaire, et la valeur de concentration moyenne sur la meme periode a ete evaluee a plus de 34 g.l-1 dans le sous bassin controle par la station de Sidi Aek Djilali et de plus de 12 g.l-1 dans le sous bassin controle par la station d'oued El Abtal.

The sediment transport is a complex phenomenon by its intermittent nature, randomness and by its spatiotemporal discontinuity. By reason of its scale, it constitutes a major constraint for development; it decreases storage capacity of dams and degrades state of ancillary structures.The study consists in modelling the transport of sediments by HEC-RAS software in wadi Chemora (Batna, Algeria). In order to do this, we have used hydrometric data (liquid flows, and solid flows) recorded at level of the four hydrometric stations existing in watershed of wadi Chemora, the MNT of the wadi and lithologic characteristics of the wadi.In the analyses of results we used the parameters from two different floods (the first one involved the whole watershed and the second – a part of the basin) along of system of wadi Chemora (wadi Chemora and its tributaries): sediment transport capacity, volume of sediments delivered to and leaving the system and areas sensitive to erosion and sedimentation.

Climate and anthropogenic changes impact on the erosion and sediment transport processes in rivers. Rainfall variability and, in many places, the increase of rainfall intensity have a direct impact on rainfall erosivity. Increasing changes in demography have led to the acceleration of land cover changes from natural areas to cultivated areas, and then from degraded areas to desertification. Such areas, under the effect of anthropogenic activities, are more sensitive to erosion, and are therefore prone to erosion. On the other hand, with an increase in the number of dams in watersheds, a great portion of sediment fluxes is trapped in the reservoirs, which do not reach the sea in the same amount nor at the same quality, and thus have consequences for coastal geomorphodynamics. The Special Issue “Modeling and Practice of Erosion and Sediment Transport under Change” is focused on a number of keywords: erosion and sediment transport, model and practice, and change. The keywords are briefly discussed with respect to the relevant literature. The papers in this Special Issue address observations and models based on laboratory and field data, allowing researchers to make use of such resources in practice under changing conditions.

Rainfall variability of Northern Algeria was analyzed over nine synoptic stations of the National office of meteorology during the period 1950–2017. Statistical tests of Mann-Kendall and Pettitt were applied to detect a significant trend and break over monthly and annual rainfall series. Stations located at the West side of the study area showed a significant decrease of annual rainfall during December, April and May while September and November recorded an increase of rainfall over the study period. Atmospheric circulation patterns affect the rainfall variability, that is why six climate indices were correlated to mean rainfall using spearman coefficient correlation. Annual rainfall series characterized by long period of drought are significantly correlated with El Nino southern oscillation (ENSO) and East Atlantic oscillation (EA). At the seasonal scale, East Atlantic oscillation and Mediterranean oscillation (MO) are the most dominant circulation modes, particularly during wet seasons.

Cette étude porte sur l’analyse de la variabilité spatiale et temporelle des indices de précipitation, température et débit dans le bassin versant de l’oued Mina (6 048 km2) dans le Nord-Ouest algérien pendant la période de 1979 à 2013. L’application du test non paramétrique de Kruskal-Wallis sur les indices de pluies a révélé que le total annuel des pluies et le nombre maximal de jours consécutifs pluvieux présentent une grande variabilité spatiale. Le nombre de jours de forts débits diminue du nord vers le sud du bassin. Quant au test de Mann-Kendall, il a révélé une tendance décroissante du total annuel des pluies. En revanche, les températures maximales et minimales ont significativement augmenté dans le temps. Il en est de même des séquences des jours secs consécutifs, des intensités des pluies et des jours extrêmement pluvieux. Aussi, la fréquence des jours avec des forts débits a diminué alors que celle avec des faibles débits a augmenté dans les trois oueds de Mina, Haddad et El Abd. Enfin, la baisse de pluies et l’augmentation de la température ont généré une diminution des ressources en eau., This study focuses on the analysis of the spatial and temporal variability of precipitation, temperature, and discharge indices in the wadi Mina watershed (6 048 km2) in the Algerian northwest during the period of 1979-2013.The application of the non-parametric test of Kruskal-Wallis on rainfall indices has revealed that the total annual rainfall and the maximum number of consecutive rainy days show a large spatial variability. The number of days with high discharge decreases from the north to the south of the basin. As for the Mann-Kendall test, it revealed a decreasing trend in total annual rainfall. On the other hand, the maximal and minimal temperatures significantly increased with time. It was the same for the sequences of consecutive dry days, rainfall intensities and extremely rainy days. Also, the frequency of days with high discharge has decreased, while that with low discharge has increased in the three wadis Mina, Haddad and El Abd. Finally, the decrease in rainfall and the increase in temperature have generated a decline in water resources.

Particular attention has been given in recent years to precipitation and variations in climate change scenarios by modeling these phenomena at different timescales. Regional climate models enable assessing the impact of climate change at the regional and local scales. This study aims, firstly, to analyze the rainfall variability in northern Algeria, and secondly, to evaluate future seasonal rainfall variability using regional climate models of the ENSEMBLE project. A statistical test and the bias method have been used for this study. Analysis of rainfall variability using the Pettitt test during the reference period (1961-1990) reveals a significant decrease of rainfall since the 1970s at the Tenes and Oran stations, located in the northwest of Algeria. This decrease occurs during the months of December and January (in winter), and March and April (in spring), and is associated to a reduction of 10-20 and 20-50 mm of daily rainfall, respectively, while the rainfall increases in the eastern region. Simulated data of 12 regional climate models have been compared to observations carried out during the reference period (1961-1990) using the bias method. Future seasonal rainfall variability was analyzed for two projection periods: 2021-2050 and 2070-2099. Most often, models underestimate the wet seasons and overestimate the dry seasons during the reference period. The models simulated a significant decrease of future rainfall in winter and spring over the two projected periods. Further investigations must be conducted to explain the underestimation of the models. It is also important to reconsider uncertainties that affect the results of this study.

Determining the link between rainfall and flow for a watershed is one of the most imperative problems and challenging tasks faced by hydrologists and engineers. Conceptual and Box-Jenkins hydrological models represent suitable tools for this purpose in circumstance of data Scarce and climate complexity. This research consists in a comparative study between conceptual models and Box-Jenkins model, namely, GR2M, ABCD, and the autoregressive moving average (ARIMA) which has a numerical design. The three models were applied to three catchments located in the north-west of Algeria. Basins have been selected according to the availability of long-time series of hydrological and climatic data (more than 30 years) to calibrate parsimonious models, taking into account the climatic variables and the stochastic behavior of the natural stream flow. Overall, the conceptual models perform similarly; whereas the results show that the GR2M model performed better than the ABCD in the validation stage, the stochastic model shows better results as opposed to conceptual models in the case of the Mellah Wadi which presents high permeability in its behavior. This is due to the simplicity of the model needed for data (only runoff data) and the ability of the stochastic model to produce stream flow in complex catchments. Such circumstance could be caused by different motivations. On the one hand, the diverse number of model parameters that make the ABCD the less parsimonious approach, with four parameters to be calibrated. On the other hand, the inability of the ABCD and the ARIMA model to capture and describe the groundwater processes, important for the cases study. Moreover, the validation period includes a large drought period, started in the late 1980s, which makes difficult model adaptation to different hydrological regimes.

Many studies have highlighted breaks in mean values of temperature and precipitation time series since the 1970s. Given that temperatures have continued to increase following that decade, the first question addressed in this study is whether other breaks in mean values have occurred since that time. The second question is to determine which climate indices influence temperature and rainfall in the coastal region of Northern Algeria. To address these two questions, we analyzed the temporal variability of temperature and annual and seasonal rainfall as they relate to four climate indices at seven coastal stations in Algeria during the 1972–2013 period using the Mann–Kendall, Lombard, and canonical correlation (CC) analysis methods.The annual and seasonal maximum, minimum and mean temperatures increased significantly over that time period. Most of these increases are gradual, implying a slow warming trend. In contrast, total annual and seasonal rainfall did not show any significant change. CC analysis revealed that annual and seasonal temperatures are negatively correlated with the Western Mediterranean Oscillation (WeMOI) climate index that characterizes atmospheric circulation over the Mediterranean basin. On the other hand, rainfall is positively correlated with a large-scale atmospheric index such as the Southern Oscillation Index.

The objective of this study is to estimate the extreme floods corresponding to different recurrence intervals in Trois Rivieres watershed, a large sub-basin of the Macta basin (NW-Algeria). Two regional models are used flow-duration-frequency (Qdf) modelling and gradex method. A methodology for modelling QdF curves based on the so-called continuous converging model has been applied. The second model is gradex method which is a rainfall-runoff probability approach to computing extreme flood discharges in a river. The QdF model gives a complete description of the flood dynamics of Trois Rivieres basin. Nevertheless, it is recommended to use this method with vigilance for the predetermination of severe floods for important return periods. However, the gradex method overestimates the extreme floods for different recurrence intervals. This study highlights that diverse methods should be employed for the regional analysis of extreme hydrological events.

The process of securing water supply is one of the biggest problems in the world. Along with the ever-increasing demand for water for different users, water resource management agencies face many challenges, some of which may be an obstacle to achieving sustainability and guaranteeing water for the various sectors of water supply. To face this dilemma, integrated water resources management is the best approach. The region of Tipaza is facing this problem. Through this work the WEAP model is applied to assess and analyze the current and projected balance of water resource management taking into account the different policies and operational factors that can affect the demand up to the year 2050. The results of the simulation showed that a deficit of 18.936Mm3 will be registered in the year 2042. For the years 2043 and 2044, the demand will be of the same order as the supply. For the period 2045 to 2050 a deficit of (3.44Mm3 to 85.48 Mm3) will be recorded in the case of scenario RCP4.5. On the other hand, in the case of the pessimistic scenario RCP8.5, the deficit will start from the year 2025 and will continue until the horizon of the year 2050 with 130.95 Mm3.

The objective of this study was to follow-up on the evolution of the hydro-pluviometric schemes and particular elements of Wadi Mina (6048 km(2)) to the Sidi M'Hamed Ben Aouda Dam to evaluate the silting origin and status of this dam situated in the northwest of Algeria. The pluviometric study targeted a series of rains during 77 years (1930-2007), the liquid discharge data cover a period of 41 years (1969-2010) and the solids and suspended sediment concentrations data cover very variable periods, starting from 22 to 40 years for the entire catchment area. The statistical tests for ruptures detection on the chronological series of rains and discharges indicate a net reduction of rains of more than 20% on the entire basin since 1970. The evolution of solids inputs was quantified: the maximum values are registered on autumn start and at the end of spring. The Wadi Mina basin brings annually 38 x 106 m(3) of water with a specific degradation of 860 t.km(-2) year(-1). By comparing the results found, we thus observe that the basin upstream of SMBA (1B) Dam is the greatest sediment producer towards the dam because it shows a specific degradation equal to 13.36 t.ha(-1) year(-1).

Une analyse des pluies journalieres extremes du bassin du Cheliff (plus grand bassin du Nord de l’Algerie) a ete etablie sur la periode 1971–2010. Pour cela 13 stations pluviometriques ont ete selectionnees et recueillies aupres de l’Agence Nationale des Ressources hydrauliques (ANRH). Six indices de pluies journalieres ont ete analyses pour caracteriser l’evolution temporelle de la frequence et l’intensite des pluies journalieres sur la periode d’etude. Ces indices correspondent a la pluie totale annuelle des jours de pluies ( 1 mm), aux percentiles 90, 95, 99 et 99.5% et a l’intensite journaliere des jours de pluie (1 mm). Le test de Mann–Kendall indique une tendance generale a la baisse significative pour les pluies totales et l’intensite journaliere de certaines stations. La frequence des fortes pluies ne montre pas de changement significatif de son evolution temporelle pour la majorite des stations. La recherche de relation entre les indices de pluies journalieres et les differents modes de circulation atmospherique a mis en evidence l’influence de l’oscillation mediterraneenne sur la variabilite des precipitations journalieres du Cheliff, particulierement pour les stations qui ont connu une baisse significative de leur indice de pluies journalieres

The increase in drought features in North Africa and Mediterranean regions is one of the most threatening natural hazards related to climate change. The spatial extent of this phenomenon in the North-West of Algeria has caused serious economic, social, and environmental impact with enormous losses. In this study, the return periods of drought events characterized by high severities and the three main droughts characteristics (duration, severity, and intensity) in the future under two Representative Concentration Pathway (RCP4.5 and RCP8.5) over two representative watersheds in North-West Algeria have been estimated In order to plan and manage the water resources under drought conditions.

Proceedings of Euro-Mediterranean Conference for Environmental Integration (EMCEI-1), Tunisia 2017; A great number of rivers of North Africa are equipped with many dams for multiple purposes, mainly potable water, irrigation and energy production. In most of the countries—Morocco, Algeria and Tunisia, the storage capacity exceeds the runoff capacity, which means that water is stored several times in a row during its course to the sea.

Optimal management of water resources requires the use of hydrological modeling, which makes it possible to anticipate the available water resources from a few days to a few months and thus improve their management and consultation between the various actors in the water sector.

Extreme climate events often have serious impacts on society, water resources, health and agriculture. Actually, several scientists tend to characterize these extreme phenomena by the use of extreme climatic indices. However, the analysis of teleconnection between these climate extremes indices and the indices of atmospheric oscillations is very useful for understanding the relationship and impact of these atmospheric oscillations on the occurrence and frequency of extreme climatic phenomena.

The objective of this study is to analyze the hydro-climatic regimes of the watershed of Mitidja West, and then try to evaluate the influence of climate on superficial flows. Rainfall data and databank for monthly discharges come from the National Agency of Hydraulic Resources (ANRH), rainfall are recorded from 23 rainfall stations distributed over the watershed and whose size varies from one station to another, and Time series of discharges data are generally from 1987 to 2012, but vary in duration. However, we noted that flows have been subjected to ruptures of 1975 until the middle of the 1980s. However, this reduction is due to a the climate impact associated with precipitation which decrease significantly since the end of the 75 years; or an anthropogenic impact due to the many hydraulic infrastructure development since 1985. Thus, for the simulation of the discharges from the rains, the efficiency of the model to simulate monthly discharges of the basin is given by the analysis of the criterion of Nash, of which it gave satisfactory values ​​superior to (60%), we can say, afterwards, that the GR2M model has a certain efficiency to simulate the discharges in the monthly time step and to guarantee a better understanding of the hydrological behavior of the basin.

The estimation of precipitation quantileshas always been an area of great importance to meteorologists, hydrologists, planners and managers of hydrotechnical infrastructures. In many cases, it is necessary to estimate the values relating to extreme events for the sites where there is little or no measurement, as well as their return periods. A statistical approach is the most used in such cases. It aims to find the probability distribution that best fitsthe maximum daily rainfall values. In our study, 231 rainfall stations were used to regionalize and find the best distribution for modeling the maximum daily rainfall in Northern Algeria. The L-moments method was used to perform a regionalization based on discordance criteria and homogeneity test. It gave rise to twelve homogeneous regions in terms of L-Coefficient of variation(L-CV), L-Skewness (L-CS)and L-Kurtosis (L-CK). This same technique allowed us to select the regional probability distribution for each group using the Z statistic. The generalized extreme values distribution (GEV) was selected to model the maximum daily rainfall of 10 groups located in the north of the steppe region and the generalized logistic distribution (GLO) for groups representing the steppes of Central and Western Algeria. The study of uncertainty by the bias and RMSE showed that the regional approach is acceptable. We have also developed maximum daily rainfall maps for 2, 5, 10, 20, 50 and 100 years return periods. We relied on a network of 255 rainfall stations. The spatial variability of quantiles was evaluated by semi-variograms. All rainfallfrequencymodelshave a spatial dependence with an exponential model adjusted to the experimental semi-variograms. The parameters of the fitted semi-variogram for different return periods are similar,throughout, while the nugget is more important for high return periods. Maximum daily rainfall increases from South to North and from West to East, andis more significant in the coastal areas of eastern Algeria where it exceeds 170 mm for a return period of 100 years. However,it does not exceed 50 mm in the highlands of the west.

This work aims, as a first step, to analyze rainfall variability in Northern Algeria, in particular extreme events, during the period from 1940 to 2010. Analysis of annual rainfall shows that stations in the northwest record a significant decrease in rainfall since the 1970s. Frequencies of rainy days for each percentile (5th, 10th, 25th, 50th, 75th, 90th, 95th, and 99th) and each rainfall interval class (1–5, 5–10, 10–20, 20–50, and ≥50 mm) do not show a significant change in the evolution of daily rainfall. The Tenes station is the only one to show a significant decrease in the frequency of rainy days up to the 75th percentile and for the 10–20-mm interval class. There is no significant change in the temporal evolution of extreme events in the 90th, 95th, and 99th percentiles. The relationships between rainfall variability and general atmospheric circulation indices for interannual and extreme event variability are moderately influenced by the El Nino-Southern Oscillation and Mediterranean Oscillation. Significant correlations are observed between the Southern Oscillation Index and annual rainfall in the northwestern part of the study area, which is likely linked with the decrease in rainfall in this region. Seasonal rainfall in Northern Algeria is affected by the Mediterranean Oscillation and North Atlantic Oscillation in the west. The ENSEMBLES regional climate models (RCMs) are assessed using the bias method to test their ability to reproduce rainfall variability at different time scales. The Centre National de Recherches Meteorologiques (CNRM), Czech Hydrometeorological Institute (CHMI), Eidgenossische Technische Hochschule Zurich (ETHZ), and Forschungszentrum Geesthacht (GKSS) models yield the least biased results.

The exposure of the Earth’s surface to the energetic input of rainfall is one of the key factors controlling water erosion. While water erosion is identified as the most serious cause of soil degradation globally, global patterns of rainfall erosivity remain poorly quantified and estimates have large uncertainties. This hampers the implementation of effective soil degradation mitigation and restoration strategies. Quantifying rainfall erosivity is challenging as it requires high temporal resolution(−1 h−1 yr−1, with the highest values in South America and the Caribbean countries, Central east Africa and South east Asia. The lowest values are mainly found in Canada, the Russian Federation, Northern Europe, Northern Africa and the Middle East. The tropical climate zone has the highest mean rainfall erosivity followed by the temperate whereas the lowest mean was estimated in the cold climate zone.

Due to an oversight, Figure 1 image and Figure 4 caption were incorrectly captured in the original publication.

During the past century, Algeria has been subject to frequent periods of drought, which were recorded first in 1944 and then successively in 1981, 1989, 1990, 1992, 1994, 1996 and 1999. The northwestern and central Plains of the country were particularly affected by this phenomenon, resulting in significant decrease of yields and water resources with severe damages to crops. The most important water deficit periods were recorded in 1981 and 1989 at the Chellif Plain (136 %) and in 1990 at the plains of Ghriss, Mitidja and Sidi Bel Abbes. The most common indexes used to evaluate the drought severity are (1) Palmer drought severity index and (2) the standardized precipitation index, which are useful tools in studies concerned with the long-term forecasting of water resources and management of water in agriculture, giving valuable results about the water balance within a specific system. The analysis of the relationship between annual precipitation and these three indices showed that during the period 1930–2007, precipitation was strongly related to AMO and NAO. The ENSO and NAO indices are negatively correlated with precipitations. The period of deficit starting from 1975 corresponds to a phase of increasing AMO index to reach a positive phase. On the seasonal scale, the evolution of this index is similar to that of the annual scale. The use of Markov chains for studying the interdependency of rainfall series through a long-term period showed a strong trend for a dry year to be followed by another dry period. This trend is higher in the western plains than in the centre. The results show also that the probability for a wet year to be succeeded by another wet year exceeds 50 %. These results hold for winter and spring seasons.

ResumeDans cette etude, on a fait appel a la teledetection et aux systemes d’information geographiques (SIG) pour evaluer et cartographier l’erosion hydrique en utilisant l’equation universelle des pertes en sol USLE dans le bassin versant de l’Oued Mina en Algerie. Ce bassin est caracterise par une grande irregularite dans les precipitations, une forte pente, une lithologie essentiellement marneuse et une couverture vegetale tres faible ce qui le rend tres vulnerable a l’erosion. L’USLE est la combinaison de six facteurs specifiques qui decrivent les caracteristiques du bassin versant. Les donnees de teledetection multi-temporelles et les SIG sont utilises pour evaluer et cartographier chaque facteur individuellement. L’integration des cartes thematiques des facteurs du modele USLE dans le SIG permet de cerner l’impact de chaque facteur dans les pertes en sol, de classer par importance relative les zones d’erosion, et de quantifier les pertes en sol dans le bassin.Editeur Z.W. KundzewiczCitation Toumi, S...

Resume L'origine de la salinite dans les eaux de la nappe Plio-Quaternaire de la plaine de Ghriss (Nord-Ouest de l'Algerie) et la comprehension de ses comportements hydrodynamiques et geochimiques, en reponse a certains forcages naturels et anthropiques, ont ete approchees par l’etude combinee des rapports ioniques et d'analyses statistiques des donnees hydrochimiques. Cette etude a identifie l'alimentation laterale de l'aquifere Plio-Quaternaire par les deux principaux aquiferes de la region. La salinisation des eaux de la nappe Plio-Quaternaire resulte essentiellement de la dissolution des evaporites (halite et gypse), de l'infiltration des eaux de ruissellement, et du retour a la nappe des eaux d'irrigation qui sont chargees en sels initialement reconcentres dans le sol ou dans la zone non saturee. Les concentrations elevees en nitrates et en chlorures sont l'indice d'une pollution anthropique d'origine urbaine ou agricole qui affecte toute la plaine de Ghriss en proportions variables. Citation Bekkous...

In this paper, we study the impact of climate change on river regimes in several parts of Africa, and we look at the most probable causes of these changes either climatically or anthropogenically driven. We study time series of updated monthly and annual runoff of rivers of North Africa, West Africa (Sahelian and humid tropical regions) and Central Africa, including the largest river basins: Niger and Volta rivers in West Africa, and Congo and Ogooue rivers in Central Africa. The recent years are studied in the perspective of multi-decadal variability. In West Africa and in a part of Central Africa, the climate has changed since 1970, and rainfall has not returned to previous annual amounts, except in Equatorial Africa. The consequences of the long-lasting drought are, depending on the area concerned, the modification of seasonal regimes (Equatorial area), the groundwater table decrease (Tropical humid area) and the land cover degradation (Sahelian area). The increasing number of dams and of agricultural areas also plays a major role on the modification of river regimes. The population increase will continue to impact on the environment: land cover change, deforestation, agriculture and increasing number of dams will be associated with a reduction of water and sediment discharges to the sea, and major impacts on downstream ecosystems and coastal areas. It seems necessary to share with stakeholders a comprehensive approach of the water cycle from the basin to the sea, to prevent long-lasting damages to ecosystems and infrastructures. Copyright © 2013 John Wiley & Sons, Ltd.

Une modification des pluies va probablement entraîner une modification de la disponibilité des ressources en eau. Les impacts pour la population humaine devraient donc être importants. Les ressources en eau font aussi l’objet d’une pression anthropique qui ne cesse de croître : changement d’occupation des sols, construction de barrages, prélèvements d’eau souterraine. Le bassin versant de l’oued Mina, de 6 000 km2 environ, situé au nord-ouest d’Algérie et affluent de l’oued Cheliff, présente une variabilité spatiale et temporelle importante des pluies et des débits. Une régionalisation de la pluviométrie annuelle de ce bassin a été réalisée à partir des données de 26 stations pluviométriques ayant 77 années d’observation (1930-2007). Grâce aux tests statistiques de détection des ruptures sur les séries chronologiques, nous avons détecté une diminution des pluies annuelles de 19 à 20 % sur le bassin de l’oued Mina, vers 1976 le plus souvent, et une rupture dans les séries de débits mensuels et annuels de cinq postes hydrométriques, à partir du milieu des années 1970 et jusqu’au cours des années 1980. Sur l’ensemble du jeu de données de débits, tous les mois présentent des ruptures, et c’est durant les mois de février, mars et avril, de fin de saison humide, qu’elles sont les plus significatives. Durant les années récentes, aucun changement de tendance ne peut être observé sur les séries étudiées. À cette échelle, les pluies diminuent effectivement de manière importante et abrupte depuis 1960. Les changements climatiques qui affectent actuellement le bassin méditerranéen sont susceptibles d’avoir des conséquences importantes sur les régimes hydrologiques des fleuves côtiers., A change in rainfall will likely cause a change in the availability of water resources, and impacts on the human population should be important. Water resources are also subject to anthropogenic pressure that continues to grow: change of land use, dam construction, and groundwater withdrawals. The catchment basin of Wadi Mina, around 6,000 km2, located in northwest Algeria and tributary of the Wadi Cheliff, experiences a significant spatial and temporal variability of rainfall and discharges. The regionalization of the annual rainfall for this basin was conducted using data from 26 rainfall stations with 77 years of observations (1930-2007). Using statistical tests for detecting breaks in time series, we showed a decrease of 19-20% in annual rainfall over the Wadi Mina basin, mostly around 1976, and a break in time series of monthly and annual discharges at five gauging stations, starting in the mid-1970s and continuing until the 1980s. Over the whole studied discharge time series, we detected a decrease for all months, but it is mainly during the months of February, March and April, i.e., the end of the humid season, that they are the most significant. During recent years, no trend has been observed. At this scale, rainfall actually decreases significantly and steeply since 1960. Climate change currently affecting the Mediterranean is likely to have important consequences on the hydrological regimes of coastal rivers.

Assessment of aquifer vulnerability to contamination is an effective tool for the delineation of groundwater protection zones. Geophysical approach was used to determine vulnerability zones in a study area located at 70 km north part of In Salah region, Southern limits of hydrogeological occidental basin in the outcrops Continental Intercalaire terrains. Ninety vertical electrical soundings (VES) were conducted in the study area. The results from the electrical survey data were used to assess the potential risk of groundwater pollution and define the protective properties of geologic layers as well as identifying suitable areas with poor, moderate, and high aquifer protective capacity rating. The inverted resistivity values and thickness of the layers above the groundwater table were used in order to estimate the integrated electrical conductivity (IEC) that can be also used for the quantification of aquifer vulnerability.

Erosion, sediment transport, and deposition result in agricultural soil degradation, dam siltation, and significant and costly damage. In Algeria, despite a decrease in total rainfall, especially in the central and western parts of the country, dam siltation and erosion are on the rise according to recent studies by the National Agency of Dams and Transfers. Developing a map of the spatial variation of rainfall erosivity will provide a powerful tool for land and dam managers. Erosivity can be quantified using the R factor from the Universal Soil Loss Equation. The purpose of this work is to develop a model for estimating rain erosivity based on the modified Fournier index (MFI), longitude, altitude, and mean maximum daily rainfall, and then to produce a map of the spatial distribution of erosivity in Northern Algeria. The R factor reaches a maximum value of roughly 905 MJ mm ha−1 year−1 in the Jijel area of Mediterranean Eastern Algeria and a minimum value of 37 MJ mm ha−1 year−1 in the southern portion of the study area. The study of the temporal evolution of annual rainfall erosivity index (R) and I max over 30 min showed that R recorded a negative trend and I max recorded no trend.

L’Algerie, et en particulier la region Ouest, a connu ces dernieres annees de nombreuses catastrophes liees au phenomene des crues (Alger en 2001, Ghardaia en 2008…). Le choix comme zone d’etude du bassin-versant de la Tafna est lie a la forte recurrence des evenements catastrophiques dans cette region de l’Ouest algerien. Le present article s’interesse a la description et a la caracterisation de la puissance des crues de la Tafna sur la base du calcul du coefficient e de Myer-Coutagne-Parde. Les crues extremes de la Tafna se concentrent generalement en automne et au printemps, avec une occurrence tres marquee des evenements exceptionnels pendant le mois de mars pour pratiquement l’ensemble des stations etudiees. Par ailleurs, l’oued Sebdou a Beni Bahdel et l’oued Mouileh a Sidi Belkheir presentent d’importantes crues estivales. De plus, la classification de Parde sur la base du calcul du coefficient e demontre que les crues du bassin-versant de la Tafna peuvent etre qualifiees de mediocres a fortes, en comparaison des resultats obtenus pour les grands cours d’eau europeens et africains. Bien qu’avec des intensites variables, la majorite des crues dans cette region a ete devastatrice, ce qui laisse a penser que le phenomene meteorologique a ete amplifie par l’activite humaine, notamment par une urbanisation anarchique et un developpement des installations et des activites economiques dans des zones inondables, en plus des crues eclairs qui caracterisent certaines regions de l’Algerie telles que la Mekerra.

Algeria is one of arid and semi-arid areas, which suffer from long-period drought. Of severe rainfall deficits, adverse consequences on the environment, socio-economic development, water resource quality and quantity, increasing soil degradation. The study area is part of the basin of Wadi El Hammam (western Algeria). A wet period between 1943 and 1975 occurred. A second period of drought occurred during the period 1975 to 2004.The average annual flow is 3.52 m 3 / s (19682004). Thus, four different layers were identified: groundwater, ground limestone lake, the water sands and sandstones and dolomitic limestone aquifer.

We analyzed the temporal variability of annual precipitation measured at five stations in the Macta (14,380 km2) and Tafna (4,949 km2) catchments located in northwestern Algeria, in connection with climate indices over the 1950–2004 period. Analysis of the temporal variability using linear regression and Pettitt test revealed a significant decline in annual rainfall in the mid-1970s in both basins. Furthermore, a decrease of at least 20% of total annual rainfall is also observed at all five stations. As for the relationship between climate indices and variability of annual precipitation, canonical correlation analysis shows that, from 1950 to 2004, precipitation at the five stations are negatively correlated with NINO4 and, to a lesser degree, with NAO.

The functioning of karst systems in the Tlemcen Mountains, Algeria, was studied using environmental isotopic and chemical parameters. The weakly enriched values of 18O suggest a fast infiltration of water through the karst systems. The deuterium (2H) excess in groundwater and tritium (3H) in precipitation show that the region is subjected to Mediterranean and Atlantic influences with a predominance of the former. The isotopic gradient, in combination with topographic and geologic criteria, allows the recharge areas of the main karst systems to be estimated. The results of 13C, 14C and 3H analysis show that the majority of present waters come from perched systems and mixture waters influenced by three clusters (“ante-thermonuclear” waters, “thermonuclear” waters, and present waters) that generally emerge from semi-confined systems. The oldest waters are relatively rare and are stored in deeply confined systems. These results are consistent with the hydrochemical and the hydrogeological findings. The results have important implications in groundwater protection.

The quality of the Upper Cheliff groundwater, located in North West Algeria, has in recent years undergone serious deterioration due to uncontrolled discharge of urban wastewaters, intensive use of chemical fertilizers in agriculture as well as to overexploitation. This study aims at analyzing the flow pattern of the Upper Cheliff groundwater, determining its current hydrochemical status and understanding the mineralization processes involved in its chemical quality. Two piezometric and sampling campaigns were carried out in 2008 in high water (April) and low water (October) periods. The major chemical ions (Ca2+, Mg2+, Na+, K+, Cl−, HCO3 −, NO3 −, SO4 2−) were analyzed in all samples. The piezometric data were mapped and allowed to analyze the groundwater flow conditions, in particular at the boundaries of the aquifer. The interpretation of hydrochemical data was made using various methods (Piper diagram, Stabler classification, base exchanges index, bi-elements scatter diagrams, saturation indices, mapping and multivariate principal component analysis). The results provide a better understanding of this aquifer hydrogeology and hydrochemistry. Several hydrochemical types (chloride-calcium, chloride-sodium and bicarbonate-calcium) characterize the groundwater. Mineralization processes and the origin of salinity are determined by the lithology of the aquifer (dissolution, base exchanges), and by climatic (evaporation) and anthropogenic factors (agricultural and urban wastes). The groundwater in the Upper Cheliff is currently of poor quality. This status is worrying, as this groundwater is an important natural resource for the socio-economic development of this region. Urgent measures must be taken to preserve this resource.

Algeria is periodically affected by severe and repeated flooding. Flood hazard studies require the estimation of extreme flood flows. To predict and estimate the characteristics of maximum flows, knowledge of their distribution law is essential. The L-moments method was used to determine homogeneous regions and the appropriate distribution for these regions. Three homogeneous regions were delineated. This technique produced a Pearson type III distribution for the coastal region and the Tell Atlas and a Pareto distribution for the steppe regions and high plateaus of Eastern and Western Algeria. To estimate maximum flow at ungauged sites for different return periods, the 'index-flood' method was used. An empirical formula was developed that uses the average annual maximum flow as a function of catchment area and the average slope of the main channel to estimate maximum flow at any point on the Oued. The coefficient of determination and the Nash criterion, for the three regions, are superiors to 88% and 83% respectively. The root mean squared error, for the three regions, is less than 12%. These values show the robustness of the developed models.

The watershed of the studied region, part of the large basin of Macta situated in the north-west of Algeria, is submitted to flash floods and is particularly dangerous. Facing to the recurring of those catastrophic events, the understanding of hydrologic process constitutes a strategic axis of prevention against floods. Functioning indicators of the basin have been searched for by modelling of the flow on different floods observed at level of the stations established along Mekkera wadi. Among hydrologic models, the Muskingum model has been chosen for floods propagation study and estimations of flows, and the QdF model is used to evaluate the extreme quintiles and build the hydrographs of different return periods. The floods episodes observed at level of stations of Sidi Ali Benyoub and of Sidi Bel Abbes are characterised by importance of damages caused. The town of Sidi Bel Abbes built in the major bed of Mekkera and so the communes situated in the plains are the most exposed to these sudden floods.