Continental Intercalary Research Articles

Characterization study of the Albian reservoir of southern Algeria

Deep oil and hydraulic drillings that have reached the Albian aquifer also called the Intercalary Continental aquifer testify that this is an important reserve of thermal water that constitutes the main geothermal resource in southern Algeria. The main purpose of this study is to define the structural characteristics of the Albian reservoir of southern Algeria such as localisation and structure, depth, thickness, and piezometric level. For this purpose, we have realized characterization maps using data from petroleum drillings of Sonatrach (National Society for the Research, Production, Transportation, Processing and Marketing of Hydrocarbons) and hydraulic boreholes of ANRH (National Agency for Water Resources) of Algeria.

GROUNDWATER OVEREXPLOITATION OF THE CONTINENTAL INTERCALACRY AQUIFER. A CASE STUDY FROM GHARDAIA, ALGERIA

Since the late 1999, extensive groundwater extraction within the Sahara aquifer system has been investigated. In this study we analyze the overexploitation of the thermal groundwater stored in the Continental Intercalary aquifer in the Algerian province of Ghardaia. The Saharan aquifer system is recognized by a large number of over 8800 boreholes and springs, on which 3500 operate the Continental Intercalary series and 5300 operate the Terminal complex. This work describes the groundwater order problem of overexploitation and the flows that exploit this hydrothermal system to be identified and analyzed. We have negative impacts on groundwater in that region due to the practice of certain activities which directly affect the quantity causing the water level of the aquifer to be lowered. Using theoretical context, water quality status can be assessed and recommendations suggested. Results show that we have 387.86 million m3/yr of flow today which is determined 30 m drawdowns. Measures need to be taken until the effects of the appeal become irreversible and the legal system instruments need practical applicability to prevent this context from extending to other areas.

Use of Hydro-chemical Tools to Improve Definitions of the North-Western Sahara Aquifer System, Case of Ouargla Groundwater, Algeria

The North-Western Sahara Aquifer System (NWSAS) is a complex multi-layered aquifer system with extraordinary continental groundwater reserves. This largest aquifer in the world straddles three countries: Algeria, Libya, and Tunisia. It contains more than 50,000 billion cubic meters of water; of which, 70% is in Algerian territory in the southeast of the country. This water is the result of accumulation over 1 million years. In the Wadi Mya basin (Algeria), this system is characterized by two overlaid aquifer systems: the complex terminal (CT), a shallow aquifer housed in the Senonian-Eocene and Mio-Pliocene formations, and the continental intercalary (CI), a deep aquifer hosted in the Albian, Aptian and Barremian formations. The main purpose of this study is to carry out a correlation between the geochemical composition of the water and the facies of the aquifer formation. The adopted approach will allow deciphering the hydro-chemical relationships between the different levels of the two aquifer systems in the Wadi Mya basin. To acquire the chemical composition of water, the study method goes through a targeted sampling and physicochemical analysis of water followed by a statistical analysis as well as correlation and geochemical modelling: the interpretation of specific diagrams (Piper), correlations between chemical elements in binary graphs, and principal component analysis (PCA). The performed geochemical modelling by examining the saturation index and chemical balance of water helps to better understand the origin of mineralization, elucidate the mixing of waters originating from different aquifers, as well as highlight the relationship between deep and shallow aquifers in the Wadi Mya Basin hydrodynamic conversion. The obtained results indicate that the overall mineralization occurring within the study area is dominated by sodium chloride and calcium chloride-sulfate facies. This can be explained by the dissolution of halite, gypsum, and anhydrite evaporitic rocks, intercalated in the aquifer matrix besides the effects of the extended stay of fossil waters with low recharging and cation exchange reactions resulting from water-rock interactions. The interference recorded between the geochemical signatures of the two aquifers favors the hypothesis of interconnection between aquifers through fractures. Through the implementation of such academic research, this invaluable source of life will stay sustainable for future generations.

Stratigraphy, palaeontology and sedimentology of the Upper Cretaceous of northern Tademait (Sahara, Algeria)

Thorough sedimentological and palaeontological analyses of four expanded Upper Cretaceous sections in northern Tademait had allowed us to address and reconsider the stratigraphical framework of the so-called ‘Continental Intercalary’ and ‘Hamada series’ in this remote Saharan area. These four sections (i.e., Meguidene, Gara Samani, Oued El Mezaourou-Gour Louazouaza, and El Menia) document Upper Cretaceous strata overlying post-Palaeozoic substrata and ranging from the clastic Gara Samani Formation (of supposed early Cenomanian age), through the El Golea Clays (lower–middle Cenomanian), the Gour Louazouaza Formation (lowermost upper Cenomanian, with the Oued El Mezaourou Limestone Member ranging from the Neolobites vibrayeanus to the Vascoceras gamai ammonite zones of the uppermost Cenomanian, and the Marls of Gara Mta El Mar Member of the Choffaticeras sinaiticum ammonite Zone in the lower, but not lowermost, Turonian), to the Ain El-Hadjaj Formation (of alleged Campanian age). Most efforts have concentrated on the ‘mid’-Cretaceous deposits that yield vertebrates and diversified ammonite and macrofossil assemblages. In spite of these improved correlations, further bio-chronostratigraphical data are needed in order to constrain the stratigraphical gap within the Gour Louazouaza Formation at the Cenomanian–Turonian boundary (C/TB) better. The succession studied can be correlated with other similar-aged sections in North Africa and illustrates the development of braided fluvial and aeolian dune-interdune environments followed by a ramp depositional system in response to the early Late Cretaceous second-order sea level rise along the southern margin of the Tethys.

Groundwater Geochemical and Quality of the Continental Intercalary Aquifer in Béni Ounif (Southwest Algeria)

Groundwater Geochemical and Quality of the Continental Intercalary Aquifer in Béni Ounif (Southwest Algeria)

The Continental Intercalary in Algeria: Analysis, Survey and Perspectives for Green Agriculture Development

The Northern Sahara Aquifer System (NSAS) is a complex system that includes several aquifers overlying most areas. The Continental Intercalary, also known as the "Albian groundwater" is an aquifer with impressive characteristics. It extends over three countries: Algeria, Tunisia and Libya. Intended for crop irrigation, the boreholes drilled in this Algerian aquifer, the boreholes carried out on this aquifer are artesian in their totality, with flows and pressures reaching in some places considerable values, of the order of 0,4 m3.s-1 for the flow and 3.106 Pa for the pressure. These two parameters are necessary to appreciate the energy potential of the Albian groundwater. A survey of the Continental Intercalary was carried out to study its energy potential. We were able to gather all possible data concerning the boreholes in the Algerian aquifer part. The study covered 295 boreholes that were identified and well documented, spread over 3 regions in southern Algeria. The water from the artesian boreholes in the Albian groundwater is transported to storage basins (for drinking water supply, irrigation and industry) for later use, or distributed directly to users after lowering the temperature of the water in the cooling towers. In these operations, all the hydraulic energy is lost and external energy is required from the electricity grid to meet the needs. The cumulative energy potential of all the boreholes identified has reached the theoretical value of 168GWh/year, the equivalent of 14520 toe (ton of oil equivalent) that are lost annually. Best management of this natural resource will not only enable resilient and sustainable management of the production systems and the environment, but also the energy needed to cool the water, as well as the energy needed for the maintenance of the boreholes and the facilities in the direct neighbourhood.

Assessment of Spatial Distribution and Temporal Variations of the Phreatic Groundwater Level Using Geostatistical Modelling: The Case of Oued Souf Valley—Southern East of Algeria

Since the beginning of the 1980s, several regions in the northern Sahara of Algeria have been confronting the rising groundwater. Among all these regions, Oued Souf Valley represented one of the most acute affected by this phenomenon. Due to the natural topography and the insufficient/weakness of water management and miscoordination between different sectors that are represented by intensive exploitation of deep groundwater reservoirs which returns to the shallow aquifer, absence of sewage and drainage network, leakage from drinking water supply system, the groundwater has raised to the surface or near to the surface, affecting the traditional cultural environment and urban areas and degrading all socio-economic aspects of the Oued Souf habitants. To preserve the Oued Souf environment, a vertical drainage system has been constructed. Consequently, in this research, an evaluation of the vertical drainage system performance and its impact on groundwater level stabilization has been performed by mapping the water table of the phreatic groundwater level using geostatistical modeling using ordinary kriging (OK) interpolation method, which has been applied to analyze the spatial and temporal structure of groundwater level fluctuation. Meanwhile, hierarchical cluster analysis (HCA) was applied for grouping the wells based on the groundwater fluctuations for 2008, 2009, 2014, 2016, 2018, and 2021. However, the vertical drainage system reflected a significant decline of groundwater from 2009 to 2018 due to the important drained volumes through it but another rising phenomenon might be threatening the region in the near future and this is what was indicated in the 2021 groundwater level data. Cluster analysis has generated four groups based on their fluctuation means that are increasing from the first group to the fourth group ascendingly. The first cluster grouped the drains that have a shallow depth (average mean of 5.91 mbgl) and declined over the clusters. The clusters are spatially combined with significant separation of the fourth cluster which represents the deepest group (12.89 mbgl). Based on this research, several factors are influencing the stability of the phreatic groundwater level and even the performance of the drainage system, the most important of which is the overexploitation from deep groundwater reservoirs such as complex terminal and continental intercalary (in drinking and irrigation) and even the illegal use of the phreatic groundwater with important quantities for irrigation and illegal industries.

The Lower Cretaceous “Continental Intercalaire” around Tidikelt (Central Sahara, Algeria): Sedimentology, palaeontology and ichnology

The Lower Cretaceous strata are exposed over a large surface in the northern part of the Ahnet basin. They consist of transgressive, horizontal formations overlying the folded Palaeozoic formations by angular unconformity across the Tidikelt region. The present study addresses the respective lithostratigraphical units of the “Continental Intercalaire” succession and their subsequent palaeo-environment in the Tidikelt area using a trace fossil analysis combined with sedimentological and palaeontologic data. The lithological and sedimentological features of the study sections recognised eleven sub-units organised within four lithological units: the Lower Clay Unit of Barremian-Neocomian age consisting of three Sub-units (Akablie Sandstone, Sidi Mahmoud Clays and Pebbly Sands); the Quartzite Sandstones Unit referred to a Late Barremian-Early Aptian age; the Middle Clay-Sandstone Unit consisting of a thick deposit of Early Aptian-Albian age, divided into five Sub-units (Tit Sandstones, In Salah Sand-Clay, In Salah Sandstone, Foum El Bouib Sandstone, and Sandstone-Clay); and the Upper Clay Unit comprising the Oued Taleh Sand and the El-Golea Clays Sub-units. Vertebrate remains all evidence a Late Albian-Early Cenomanian age for the top part of the Continental Intercalary. Ichnologic data analysis documents lower diversity of the invertebrate trace fossils: only ten ichnotaxa are recorded so far and grouped in five ichnoassemblages. Fuvial-lacustrine ichnoassemblage represents a continental ichnofacies of a fluvial-lacustrine environment: Mermia, Scoyenia and Skolithos ichnofacies. Fluvial Ichnoassemblage of the Quartzite Sandstone Unit is represented by insect trace fossils typical of the Coprinisphaera ichnofacies. Fluvio-marginal ichnoassemblage corresponds to a tidal-influenced, fluvial deposit transgressive on Unit B, represented by Skolithos and Psilonichnus ichnofacies. Lower shoreface ichnoassemblage shows the upper part of Unit C, documented by horizontal trace fossils such as Thalassinoides and vertical root traces, all supporting a lower shoreface environment in a semi-arid climate interlined by well-oxygenated episode with nutrient-rich conditions and vegetation dominance. Near to shoreface ichnoassemblage coincides with the upper unit D of coastal deposits with fluvial-tidal influence at the base (Oued Taleh Sands) associated with Scoyenia and Skolithos trace fossils and lagoon deposit of the El-Golea Clays Sub-units.

Using GIS and Geostatistical Techniques for Mapping Piezometry and Groundwater Quality of the Albian Aquifer of the M’zab Region, Algerian Sahara

The M’zab region is subject to an arid Saharan climate where surface and sub-surface waters are of little importance. The Albian Aquifer, commonly called Continental Intercalary (CI), main component of North Western Sahara Aquifer System (NWSAS/SASS), constitutes the most extensive aquifer formation of the region. In our study area, the CI is identified, as a regional subset, as the Albian Aquifer of M’zab Region (AAMR). Its groundwater resources are considered the only source available to meet the growing needs of drinking water supply, agriculture and industry. This aquifer is heavily exploited by a very large number of wells (more than 750). Its supply is very low, so it is a very low renewable layer. This requires periodic monitoring and control of its piezometric level and its physico- chemical quality. The objective of our study is to know the current state of this aquifer, while studying the variation of its piezometry for the period 2010-2018, and also the chemical quality of its groundwater by analyzing more than 90 samples over the entire study area. The application of geostatistics by kriging and the steps of analysis, modelling and calculation of semivariogram have enabled us to draw up maps of the various hydrogeological and hydrochemical parameters. As a result, twelve thematic maps were gridded using Geostatistical tools of ArcGIS software. The water-level-change map showed a significant drop in the groundwater level over the entire M’zab region and especially around the major cities (Ghardaïa, Berriane, Metlili and Zelfana) with more than 8 meters. Chemical analyses of the Albian groundwater in the study area show the dominance of evaporite facies (Cl--Na+-Ca2+) with low concentrations than the Algerian Standards for Drinking (ASD). All the water quality indices (WQI) that have been mapped reveal that the groundwater samples were suitable for drinking and irrigation with a high quality of water located in the south of the study area.

Numerical groundwater flow modeling for managing the Gabes Jeffara aquifer system (Tunisia) in relation with oasis ecosystems

The Gabes Jeffara aquifer system, in southeastern Tunisia, is essentially recharged by rainfall infiltration and by groundwater inflow from the Intercalary Continental aquifer in the northwest. The increase in groundwater pumping for irrigation in recent decades has induced a serious decrease in groundwater levels, depletion of springs and degradation of oasis ecosystems. A multidisciplinary study was carried out to better understand the behavior of oasis ecosystems and aquifer systems and to provide tools and recommendations for water resources management. An important part of the study was devoted to developing a hydrodynamic flow model of the Jeffara aquifer system, which can be used as a future groundwater management tool considering different recharge or exploitation scenarios. This model was built with Processing Modflow, gathering data on geology, hydrogeology, hydrology, rainfall, piezometry, withdrawals and spring flow rates. The model was calibrated in steady state with reference to the piezometric levels measured in 1970 and in transient state for the period 1972–2014, using records from more than 200 wells and piezometers. The analysis of current and future water consumption was carried out with existing data, processed satellite images and farmer surveys. This analysis was used to define water demand scenarios combined with scenarios of decreased groundwater withdrawal, reinforced groundwater recharge and use of alternative water resources. The scenarios tested with the model show that the situation will be critical in less than 25 years without radical measures to reduce groundwater withdrawals by at least 60 MCM/year.

The main geothermal reservoirs in the south Algeria and their interest for local economic development

The study area is one of the important geothermal provinces in south Algeria. It is characterized by a hot arid climate with intense dryness and very high evaporation rates. The Albian geothermal system is exploited by the wells mainly for domestic and agricultural purposes. The sandstone Continental Intercalary (CI) formation constitutes the reservoir for the Albian aquifer, covering an area of 600,000 km2. This reservoir is covered by calcareous formations which yield the chemical characteristics of highly mineralized Na-Cl type representing the deep thermal waters and Ca-SO4 type determined the presence of evaporate lithology . For a better understanding of geothermal reservoir characteristic, a multidisciplinary approach was adopted, including hydrogeochemistry and geothermometry. More than fifty samples collected from wells recently in 2017 with a temperature average between 38 and 60° C and conductivities range from 2010 to 3460 μS/cm. Geochemical analysis of those thermal waters exhibits a certain degree of salinity with sodium-chloride type waters domination. The maximal geothermal reservoir temperature estimated using geothermometry is about 120°C.

The Ghout of Souf: An Original Hydroagricultural System

Abstract This article deals with the subject of the Ghouts; an old hydro agricultural system of origin of the valley of Souf which, today is in distress. Hundreds of Ghouts were flooded by the waters of the lift and backfilled. Work missions were carried out in the oases of Souf during the period 2007-2017 to try to understand the decline of this heritage. Unfortunately, it is the waters from the Albian aquifer of the Continental Intercalary and the sanitation that is the main cause of the decline of the Souf Ghouts.

Albian drilling's and its hydropower potential in Algeria: Study and exploitation

The Continental intercalary groundwater is highly sought for its water as resources hugely mobilized in Northern Sahara. A very high flow rate and output pressure characterizes this underground water. It amounts from 50 to 400 l.s-1 for the flow, and from 5 to 40 bar for pressure. A survey of the Northern Sahara Aquifer System was essential to prove the existence of this potential. This energy appears into the artesian form, which remains very considerable for a very long time in most drilling. We have realised that this energy is immense, as well as the expanded volume of the groundwater, and the importance of its use in agriculture. Unfortunately, this potential remains untapped to this day and the energy of this water is completely neglected. Several turbo generator and/or inverted pump (PATs) integration tests were undergone. The new concept of reflection with respect to the environment and sustainable development has led us to structure our work towards the extension of this potential in order to extract the exploitable energy.

Contribution to the study of the quality physicochemical of the waters of the water of the complex terminal in the valley of Oued Souf (South-East Algerian)

The area of Oued-Souf consists of a good amount of underground water resources. These resources consist of two big aquifers: the Terminal Complex and the Continental Intercalary. The Chemical quality of these waters creates big problems like: the high mineralization and the concentration of some elements that surpass the recommended norms stated by the OMS. The objectives of the present study relate to quality of the waters within this area and their effects on the environment. According to the results obtained from the different methods utilized, diagram and statistical tool, it could be said that the mineralization of these waters is geologic in origin. The mineralization relate to the composition of the strata that make the two layers. The problem of the Oued-Souf area waters is in essence a problem of quality, for this we believe there must be some rigorous research to develop the chemical quality of these waters and to guarantee their accountability to the international norms before mobilizing them to the consumers.

The use of multivariat statistical methode to study the aquifer system of terminal complex water in the Wadi Righ Valley Area (Southern Algeria)

Groundwater resources in the wadi Righ valley are presented by two major aquifers: Intercalary Continental and Terminal Complex. From a qualitative point of view, various studies have highlighted that the waters of this region showed excessive mineralization, including the waters of the Terminal Complex (EC = 5854.61µS / cm) .The present article is a statistical approach by two multi methods various complementary (ACP, CAH), applied to the analytical data of multilayered aquifer waters Terminal Complex of the Wadi Righ valley. The approach is to establish a correlation between the chemical composition of water and the lithological nature of different aquifer levels formations, and predict possible connection between groundwater’s layers. The results show that the mineralization of water is from geological origin. It concerns the composition of the layers that make up the Terminal Complex. Keywords: Terminal Complex (CT); Mineralization; Statistical Approaches; wadi Righ: Algeria

Spatial variation of the water rising and water table salinity in the Basin of Ouargla (Algerian Sahara)

The increase of waters requirements for both the needs of drinking water supply that the needs of industries and agriculture has pushed the services concerned of the hydraulics to develop a number of drilling capturing the aquifers of terminal complex (CT) and the continental intercalary (CI). This exploitation of groundwater has proved to be excessive which has created an imbalance of the water table and subsequently this situation has led and contributes in a direct way to the water table rising in Ouargla basin.The study shows that the problem of water rising has had serious effects on the physical degradation of soils by the congestion that it causes and the formation of gypseous crusts, compact, as well as the chemical degradation by the salinization of soils. The results of the study also show that the risk of salinity is proportional with the piezometric level of water table depth. The obtained values are too high and exceeds the authorized standards of water salinity, for instance the degree of water table salinity vary from: 2.4 g.l-1 and reaches 150 g.l-1 in some regions of Ouargla Basin.

Sources of chemistry of the albian water under arid conditions. Application to the western regions of the Algerian Sahara

The study has been carried out in the zones of Tout, Gourara and Tidilket that are stretching on the two Algerian biggest states in the south (Adrar and Tamanraset). This zone is known by its hyper-arid climate and sediments heterogeneity of its formations. This later has one of the biggest aquifer in Africa ascribed to the Albian. It is recognized by Continental intercalary and fossil aquifer as well that is weakly renewable. The aquifer is wildly subjected by an overexploitation in order to satisfy the needs of the agglomerations in water. From hydro chemical point of view, the interaction water-rock is the responsible factor about the mineralization of waters. The objective of the present study is to highlight again the influence of the lithology on the chemistry of the Albian water, which was rarely studied in an arid context of Sahara.Moreover, our contribution focuses on the hydrogeochemical approach in order to put in evidence the chemistry acquirement mechanism of waters that is contained in aquifer's formations.The results reflect that the influence of the aquifer matrix rich in particles, evaporates, carbonates, silicates and fluorine provide the aquifer with waters relatively mineralized, rough and with contents in fluorine that exceed the admitted norms by the WHO.

Evolution and Mineralization of Water Chemistry in the Aquifer systems of the Terminal Complex of the Wadi Righ Valley

Groundwater resources in the Wadi Righ valley are represents an important part into the eastern basin of the Algerian Sahara. It characterized by a superposed of two main major aquifers: the former represented by the Intercalary Continental (IC) and the latter by Terminal Complex (TC). This study is focused on the quality aspects of water hosted into Terminal Complex which chow a multi-layers lithology. From a qualitative point of view, various studies have highlighted indicates that the waters in this region showed displays an excessive mineralization, including the waters of the Terminal Complex (EC= 5854.61 S / cm). The application of geochemical methods on applied to the analytical data obtained from wells in the region where the appurtenance of water car reach different layers of the water system of multi-layered aquifer waters of Terminal Complex of the Wadi Righ valley. Therefore, the linear correlations between the chemical elements were composition calculated and it indicates water composition which reflects the water and the lithological nature of different layers of the aquifer. It highlights also the connection between different formation, and predicts possible connection of water between three levels groundwater's in these's layers on one hand and it indicates the mineralization origin of water that represented by the influence highly influenced by various lithological formations. The results show that the mineralization of water is from geological origin. It concerns the composition of the layers that make up the Terminal Complex.

A Statistical Summary of ground water mineralization in the Aquifer of Intercalary Continental (Algerian Septentrional Sahara)

This study deals with the mineralization in the Intercalary Continental aquifer (CI) located at the Algerian Septentrional Sahara. Statistical analysis was performed on summarized data from different studies in order to identify the origin of that mineralization in a regional scale. Therefore, multivariate statistical analysis were applied on 488 representative wells such as: (1) Principal Component Analysis (PCA) and (2) Ascending Hierarchical Classification (CAH). Obtained results highlight the chemical typology of ground water. The multivariate statistics indicate a significant influence of evaporates on water mineralization as well as the dominance of chloride-sodium facies. However, the high water temperatures recorded in the eastern part of the basin suggest hydrolysis of silicates that contributes also in that mineralization. This study confirms rather the lithological host of aquifer as a main source of water mineralization.

Vulnerability assessment of an aquifer in an arid environment and comparison of the applied methods: case of the mio-plio-quaternary aquifer

Protecting the quality of water resources has become a priority in Algeria and in several countries around the world, due to droughts and proliferation of pollution sources, such as domestic and industrial wastewater discharges, raw discharges, chemical fertilizers, etc. The valley of Oued Righ, which is one of the oldest cultivated areas and one of the best known of the Algerian northern Sahara, has experienced significant population growth and appreciable agricultural development. The water needs in this region are provided from groundwater resources, contained in the aquifers of the Terminal Complex and Intercalary Continental, and topped by the Quaternary aquifer. The present study focuses on the aquifer in the Mio-Plio-Quaternary of Oued Righ Valley, in order to assess and map its vulnerability to pollution, by applying the DRASTIC and GOD methods. The comparative study, based on Kendall test, showed that the two methods present moderate agreement (W = 0.703). The statistical analysis of different vulnerability classes revealed that vulnerability assessment, using the DRASTIC method, may be represented by four classes: "Very low", "Low", "Medium" and "High", with a dominance of class "Medium" (74.30%). The GOD method resulted in vulnerability that sits between two classes, ‘Low’ and ‘Medium’, with a noted domination of class "Low" (70%).Comparison of the two vulnerability maps obtained from the DRASTIC and GOD methods shows that the DRASTIC method better represents the distribution of degrees of vulnerability to pollution in the aquifer of the Mio-Plio- Quaternary.