Origine de la salinité et des principaux éléments majeurs des eaux de la nappe phréatique de la plaine de Ghriss,Nord-Ouest algérien

Résumé

L'origine de la salinité dans les eaux de la nappe Plio-Quaternaire de la plaine de Ghriss (Nord-Ouest de l'Algérie) et la compréhension de ses comportements hydrodynamiques et géochimiques, en réponse à certains forçages naturels et anthropiques, ont été approchées par l’étude combinée des rapports ioniques et d'analyses statistiques des données hydrochimiques. Cette étude a identifié l'alimentation latérale de l'aquifère Plio-Quaternaire par les deux principaux aquifères de la région. La salinisation des eaux de la nappe Plio-Quaternaire résulte essentiellement de la dissolution des évaporites (halite et gypse), de l'infiltration des eaux de ruissellement, et du retour à la nappe des eaux d'irrigation qui sont chargées en sels initialement reconcentrés dans le sol ou dans la zone non saturée. Les concentrations élevées 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 Bekkoussa, B., Jourde, H., Batiot-Guilhe, C., Meddi, M., Khaldi, A., et Azzaz, H., 2013. Origine de la salinité et des principaux éléments majeurs des eaux de la nappe phréatique de la plaine de Ghriss, Nord-Ouest Algérien. Hydrological Sciences Journal, 58 (5), 1111–1127.

Editeur Z.W. Kundzewicz; Editeur associé S. Faye     

Life Cycle and Population Dynamics of the Polychaete Perinereis cultrifera from the Algerian Mediterranean Coast

Abstract. The polychaete Perinereis cultrifera ( Grube, 1840 ) (Nereididae) is common along Algerian coasts in algal‐covered hard bottoms. An intensive study was conducted from June 2000 to June 2001 to characterise the life cycle of an intertidal and upper subtidal population of P. cultrifera in Algeria near the Tunisian border (30 km). P. cultrifera has a 3‐year life span and reproduces exclusively by epitoky. The reproductive season is short, and spawning occurs in late April/early May when the sea‐water surface temperature starts rising. Female sexual differentiation starts in February in the second year of life; thus, the oocytes take 16 months to mature and their diameter at maturity is approximately 250 μm.     

Assessment of climate change and associated impact on selected sectors in Poland

The present paper offers a brief assessment of climate change and associated impact in Poland, based on selected results of the Polish–Norwegian CHASE-PL project. Impacts are examined in selected sectors, such as water resources, natural hazard risk reduction, environment, agriculture and health. Results of change detection in long time series of observed climate and climate impact variables in Poland are presented. Also, projections of climate variability and change are provided for time horizons of 2021–2050 and 2071–2100 for two emission scenarios, RCP4.5 and RCP8.5 in comparison with control period, 1971–2000. Based on climate projections, examination of future impacts on sectors is also carried out. Selected uncertainty issues relevant to observations, understanding and projections are tackled as well.     

Changes in low and high flows in the Vistula and the Odra basins: Model projections in the European‐scale context

A number of extensive droughts and destructive floods have occurred in Poland in the last 25 years; hence, projections of low and high river flows are of considerable interest and importance. In the first part of this paper, projections of low and high flows in the rivers of the Vistula and the Odra basins (VOB region), for two future time horizons, are presented. Projections are based on the Soil and Water Assessment Tool (SWAT) hydrological model simulations driven by results of the EURO‐CORDEX experiment under Representative Concentration Pathways 4.5 and 8.5. The VOB region covers most of Poland and parts of five neighboring countries, giving this study an international relevance. In the second part of the paper, a review of projections of low and high flows in rivers in Central and Eastern Europe is presented. Despite a substantial spread of flow projections, the main message of the modelling part is that increases of both low and high flows are dominating. The magnitude of increase of low flow is considerably higher than that of high flow. In other words, future streamflow droughts are projected to be less severe, whereas, in contrast, river floods are projected to increase, which is a challenge for flood risk reduction, water management, and climate change adaptation. There is an overall agreement of our findings for the VOB region with projections of hydrological extremes from large‐scale models forced by EURO‐CORDEX results in the European‐scale studies.     

Evaluation of Combined Base Soil Erodibility and Granular Filter Efficiency

Filters managed in zoned dams are designed according to criteria based on the grain size distribution of both filter and eroded soil. However, the constriction size distribution of the filter is the key parameter which governs the filter retention process of flowing eroded particles. To assess the filter efficiency regarding eroded particles, several filters and base soils are tested in a vertical cell with a configuration coupling erosion and filtration processes. For setting the boundary condition of eroded particles at the filter inlet, hole erosion test (HET) was performed on the base soil. The investigation of the evolution of filter behavior shows that the void ratio and the grain shape are of a great influence on filter efficiency. A new approach of filter clogging was proposed by evaluating a damage index which is affected by various parameters such as the ratio D₁₅/d₈₅ and the size of eroded particles. An approach linking the geometrical parameters (damage index) to the hydraulic conductivity leads to an estimation of the filter performance which provides a more quantifiable and realistic criterion. The results indicate that even existing criteria were not met; the tested filters remain efficient as regards to experimental data. An analytical approach based on constrictions size distribution was used and pore reduction was matched with experimental results.

     

Spatial distribution of regionalized variables on reservoirs and groundwater resources based on geostatistical analysis using GIS: case of Rmel-Oulad Ogbane aquifers (Larache,NW Morocco)

In many countries of the world, groundwater is the main source of water in arid and semiarid regions. The scarcity of water is one of the main issues in Morocco. The coastal aquifer system of Rmel-Oulad Ogbane is recognized as one of the most important aquifers in Morocco and is very well known for their role in industrial, economic, and social development. However, this role is confronted to climate change impacts and heavy abstraction rates leading to a major decline in the groundwater levels and may eventually cause a deficit water balance of the aquifer as well as a degradation of the freshwater quality by seawater intrusion. The objective of this research is to identify and evaluate the distribution and spatial changes of regionalized variables on reservoirs and groundwater resources using geostatistical analysis in Geographic Information System (GIS) software. The prediction of these variables was performed using an interpolation method: ordinary kriging in a GIS. The normality test and trend analysis were applied to each variable to select the appropriate semivariogram model (SVM) and check the results using cross-validation (CV). Hence, several kriged maps of reservoirs and water resources have been produced to be exploited by the decision maker. The studied variables related to reservoirs and hydrodynamic data have a strong spatial dependence, which show correlations in specific direction, while the hydrochemical data are mainly related to groundwater mechanisms, such as advective-diffusive transport, without any autocorrelation between data.     

Évaluation de la qualité de l'eau par application de la méthode géoélectrique : exemple de la plaine d'El Mida–Gabes nord (Sud tunisien)

The Mida plain, which is part of the North Gabès region (southern Tunisia), is characterized by the deep sandy units of the ‘Continental intercalaire’ (CI) or the limestone of the Lower Senonian. A geophysical survey, by electrical sounding (ES), was undertaken in the studied region to better characterize the deep geological structure of this plain and therefore its aquifer resources potential. The analysis of the results shows that the prospected zone is characterized by the succession of several levels with contrasted resistivities, which are often affected by faults. Among these observed geoelectrical levels, the highly conductor one could host a saline aquifer. Another geoelectrical level corresponding to the resistant bedrock detected at Oudhref horst can contain better-quality water than that of the aquifer detected in the El Mida Graben. In this work, we tried to explain the origin of the salinity of this aquifer. Thus, we hypothesise about a contamination from Jebel Zemlet El Beida through a border fault and another one from the Sebkhet El Hamma. To cite this article: A. Mhamdi et al., C. R. Geoscience 338 (2006).     

Geochemical characterization of groundwater from shallow aquifer surrounding Fetzara Lake N. E. Algeria

Hydrogeochemical investigations were carried out around Fetzara Lake, Northeast Algeria, to assess the quality of groundwater for its suitability for drinking and irrigation purposes. The groundwater chemistry is mainly controlled by the water?Crock interactions, but also influenced by other processes such as evapotranspiration and ion exchange. Groundwater samples collected, during two periods (1993 and 2007) from wells in the area were analyzed for pH, EC, TDS, Ca²⁺, Mg²⁺, Na⁺, K⁺, CO ₃ ^2? , HCO ₃ ^? , Cl^?, SO ₄ ^2? , and NO ₃ ^? . The chemical relationships in Piper??s diagram and Gibbs??s diagram suggest that groundwaters mainly belong to noncarbonate alkali type and Cl^? group and are controlled by evaporation dominance, respectively, due to the sluggish drainage conditions, greater water?Crock interaction, and anthropogenic activities. A comparison of the groundwater quality in relation to drinking water quality standards proves that most of the water samples are not suitable for drinking. US Salinity Laboratory??s and Wilcox??s diagrams and %Na⁺ used for evaluating the water quality for irrigation suggest that the majority of the groundwater samples are not good for irrigation.     

Filtrage par reconnaissance des formes d’un profil sismique vertical Vertical seismic profile filtering through the use of pattern recognition

To improve the signal to noise ratio of the vertical seismic profile recordings, we used a filtering method based on pattern recognition. It consists in recognizing along the seismic trace, corresponding to the arrivals of various events, the shape of the P wavelet considered as the training signal. This recognition is made of projections which retain only the signals similar in shape to the P wavelet, the others being attenuated according to their degree of resemblance to the training wavelet. The study undertaken on synthetic and real data shows that this method acts as an effective filter. However, it still depends on a training signal that must be well defined and identifiable.     

Simulation of water resources management scenarios in western Algeria watersheds using WEAP model

The question of water constitutes a permanent challenge for the countries of North Africa in general and Algeria in particular. For over 20 years, western Algeria region had significant rainfall deficits that resulted in severe droughts, which seriously affected the water resources in terms of quality and quantity. This research presents one of the Water Evaluation and Planning (WEAP) model applications in watersheds of western Algeria. The model is applied to evaluate and analyze the existing balance and expected future water resources management scenarios by taking into account the different operating policies and factors that may affect demand until 2030. The results showed that neither domestic demand nor agricultural demand is met for the basis year 2006. The results also showed that domestic demand can be satisfied for the considered scenarios. Demand management and development of standard of living are the necessary procedures for proper management of the available resources. However, agricultural demand cannot be satisfied for Development of Large Irrigation System scenarios. The results confirmed that WEAP software offers a solid basis to assist planners in developing recommendations for future water resource management by revealing hot spots of action.