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The main objective of this work is to select the most reliable machine learning model to predict the generated solid flow in the Tafna basin (North-West of Algeria). It is about the artificial neural networks (ANN) and long short-term memory (LSTM). The sediment load is recorded through three hydrometric stations. The efficiency and performance of the two models is verified using the correlation coefficient (R²), the Nash-Sutcliffe coefficient (NSC) and the root mean square error (RMSE). The obtained simulated solids load shows a very good correlation in terms of precision although the ANN model gave relatively better results compared to the LSTM model where low RMSE values were recorded, which confirms that the artificial intelligence models remain also effective for the treatment and the prediction of hydrological phenomena such as the estimation of the solid load in a such watershed. [ABSTRACT FROM AUTHOR]

Climate change is expected to increase in the future in the Mediterranean region, including Algeria. The Tafna basin, vulnerable to drought, is one of the most important catchments ensuring water self-sufficiency in northwestern Algeria. The objective of this study is to estimate the evolution of hydrological components of the Tafna basin, throughout 2020–2099, compared to the period 1981–2000. The SWAT model (Soil and Water Assessment Tool), calibrated and validated on the Tafna basin with good Nash at the outlet 0.82, is applied to analyze the spatial and temporal evolution of hydrological components over the basin throughout 2020–2099. The application is produced using a precipitation and temperature minimum/maximum of an ensemble of climate model outputs obtained from a combination of eight global climate models and two regional climate models of the Coordinated Regional Climate Downscaling Experiment project. The results of this study show that the decrease of precipitation in January, on average −25%, ranged between −5% and −44% in the future period. This diminution affects all of the water components and fluxes of a watershed, namely, in descending order of impact: the river discharge causing a decrease −36%, the soil water available −31%, the evapotranspiration −30%, and the lateral flow −29%. HIGHLIGHTS Impact of climate change in northwestern Africa;; Modeling a semi-arid watershed using SWAT model;; Evaluation of the influence of decline rainfall on the hydrological cycle;; The use of RCMs of Cordex project, domain Africa;; Investigation of climatic trends at monthly scale.;

The omnipresence of oysters in Cenozoic sedimentary series and their high preservation potential allowed their consideration as one of the ecological indicators for the reconstitution of the palaeoenvironments of the Neogene basins of Orania. Few researches were interested in the systematics of Messinian oysters of the Lower Chelif and Tafna basins (Freneix et al. 1988), whereas this work is the first to specify the Tortonian-Messinian oyster environments in the three Neogene basins (Lower Chelif, Tafna, M'sirda). This study was made on the basis of shell material collected from eight sections. Only shells with autochthonous character are taken into consideration for the interpretation of paleoenvironments, which is based on several references (Videt et Neraudeau, 2002; Freneix et al. 1988; Satour 2012; Satour et al. 2020). Four oysters have been identified (Neopycnodonte navicularis, Hyotissa hyotis, Crassostrea gryphoides and Ostrea lamellosa offreti), and they are included in ten oyster levels, belonging to three time intervals (C5n, C4r-C4n and C3Ar-C3An). The palaeoenvironmental distribution analysis of late Miocene oyster allowed to define a warm subtropical to cool climate for the late Tortonian stage, which becomes warm again (temperature 16–18 °C) in the Messinian. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The magnitude of the phenomenon is disproportionate in semi-arid or in temperate climates. Thus Algeria is one of the most affected countries by this phenomenon and its consequences. To enable a rapid response to the request of engineers and managers to quantify sediment transport at the outlet of a watershed, a simple, easy tool to implement was developed. The principle adopted is based on hydrometric data sets from gauging stations with seasonal and annual time steps to define a suitable method for estimating sediment production. The sediment study was conducted by analysing the daily flows. Pierre du Chat station at the outlet of the Tafna basin served as an application. The obtained results are entirely satisfactory because the correlation coefficients of model Qss = f(Q) range between 72 and 95%. This method, once refined can be generalized to all watersheds in northern Algeria.

Algeria lies in one of the most vulnerable regions facing climate change impacts during the twenty-first century. Northwestern Algeria has experienced a persistent decline in annual rainfall associated with the significant increase in temperature during the twentieth century. This variability has been accentuated since the 1980s and has had a significant impact on water resources. The primary motto of the current study is to measure the impact of climate change on groundwater resources using time series of rainfall and runoff data measured in the Tafna Basin (7245 km2) of Algeria. The application of meteorological drought indices and statistical test of Pettitt shows that a rainfall regime modification occurred around the seventies. This modification reveals a decrease of rainfall between 8.21 and 38.85% according to the stations, with an average of 17.85%. The average recession coefficients obtained by Maillet's exponential model varies between 8.90.10 and 17.06.10−2 day−1 either side of 1987, with an average increase of 45.45% and highlight a much faster drainage of the aquifers supplying the baseflow after 1987. A shortening of 1 to 11 days with an average of 6 days of the duration of the recession after 1987 was highlighted. The average water volumes mobilized by the aquifers fluctuated between 11.38 and 3.62 hm3 before and after 1987, with an average decrease of − 69.06%. These results show a decrease in the water volumes mobilized by the aquifers after 1987 and suggest a considerable decline of groundwater resources under the influence of climate change. [ABSTRACT FROM AUTHOR]

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.

Abstract A study of the terrestrial gastropods of the Pliocene-Quaternary succession of the Beni Saf sea cliff, NW Algeria, at the Playa Port locality, is presented herein. The sedimentary succession is subdivided into four lithostratigraphic units, on the basis of their lithologic and biogenic contents: the three first units (A, B and C) are of marine origin; the last unit (D) is of continental origin and includes three beds yielding terrestrial gastropod fossils, which form laterally traceable horizons. Herein, we describe the section's lithology, present stratigraphical considerations regarding its age and thoroughly described its terrestrial gastropod fossil fauna. In total, 13 species are reported here from Beni Saf: 2 caenogastropods (family Pomatiidae) and 11 stylommatophorans (family Achatinidae and superfamily Helicoidea). The sedimentological data indicate that the depositional setting at Beni Saf was a dune system flanked by wadi floodplains deposits (snail levels); the ecological preferences of the gastropods largely agrees with this scenario. [ABSTRACT FROM AUTHOR]

Climate variability, non-optimal water resources management and increase of human pressure are three possible factors influencing runoff and water resources in semi-arid Algerian catchments, such as the Tafna catchment (western Algeria). This catchment is subject to a semi-arid climate. In addition to rainfall impact, we examine the influence of other factors, such as geology, topography and human activity, on the runoff variability in the Tafna catchment. For this purpose, to complement the rainfall and discharge series analysis, we considered baseflow and the baseflow index (BFI). The analysis was conducted for five sub-catchments of the Tafna basin, where daily rainfall and discharge series were available for the 1976–2006 period. In the analysis, we distinguished two domains defined from the topography: a high-altitude area and a plain area. According to their geological setting, the hydrological regime is different. High-altitude catchments have a larger baseflow and BFI than catchments in the plain. This may be related to the differences in lithology, as high-altitude catchments have a large area of karstic geological formations. No significant trends or step changes were found in the annual rainfall for the 1976–2006 period. We found a decrease in the mean annual discharge of two high-altitude discharge stations (significant at the 1% and 10% levels, respectively). A decreasing trend was also found for two high-altitude catchments and a plain catchment (significant at both the 1% and 5% level). The BFI decrease is only significant for one high-altitude catchment. This is evidence of a decrease in storage within high-altitude catchments. Runoff change in the Tafna catchment could therefore be related to other factors, such as human impact, rather than to rainfall change. [ABSTRACT FROM AUTHOR]

Since the 1970s, rainfall has declined along the North African coast, while the demographic pressure has increased. Supplementing the rainfall data and water level of the Beni Bahdel dam, water isotopic signature and tree ring analyses were used to better understand the effects of climate change (lower rainfall, higher summer temperature) and the water circulation in the Tafna River basin in north-west Algeria. Changes are recommended in water storage and afforestation policies and irrigation techniques. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]