Caractérisation Des Structures Géologiques Par Analyse Morphostructurale d’Image d’Ombrage (ASAR ENVISAT Et MNT SRTM) Et Géostatistique Du Sud De La Côte d’Ivoire

This paper focuses on characterizing the structural lineaments of the South of Côte d’Ivoire by using the morphostructural analysis of shading images technique (ENVISAT/ASAR and SRTM/DTM) and the geostatistical method for a better understanding of the fractured environment. This study is carried out on the basis of techniques of backscattered radar signal and the geomorphological analysis. This technical implementation significantly improves the mapping of the fractures of the study area. The number of fractures is estimated at 778. Direction N100-110° fractures are the longest and most representative. The fracture spacing fits better into the power law. The geostatistical analysis shows that the global fracturing variogram is spatially well structured. The fracture density in cumulative lengths is therefore identified with a regionalized variable. The fracturing map that is obtained represents a basic document in the fields of hydrogeology. This paper can be used for prospecting and production drilling campaigns and can be used also in geotechnics and mining prospecting

Analyse multicritère couplée au radiocarbone en contexte de variabilité climatique pour l’identification des zones potentielles de recharge des aquifères fracturés du Sud-Est de la région de la Nawa (Côte d’Ivoire)

The aim of this study is to identify and evaluate potential recharge areas for aquifers in South-East Nawa (Côte d’Ivoire) by coupling multicriteria analysis with radiocarbon in the context of climate variability. It is based on the combination of spatial information relating to different parameters (climate, topography, soil, vegetation, geology, etc.) that can influence recharge in different ways. First, the amount of infiltrated water to recharge the aquifers is estimated from the hydrological balance after characterising the climate variability in Soubré. Then, the recharge areas of fractured aquifers are mapped by multicriteria analysis. Finally, these areas are validated by carbon 14 activities. From 1951 to 2017, the rainfall deficit on either side of the 1970 rupture is 14%. Two wet periods (1951-1970 and 1993-2017) interspersed with a dry period (1971-1992) characterize the study area. The estimated water level to recharge the aquifers is 243 mm from 1951 to 2017. The modelling of climatic, topographic, pedological, geological and vegetation parameters allowed the elaboration of well-structured thematic maps. The cross-referencing of these parameters in a GIS facilitated the design of the recharge area map of South-East Nawa. This map highlights four areas of rechargeability, validated by carbon 14 activities. The very strong (40%) and strong (35%) recharge areas are located in the South-East and extend to SouthWest of the study area. The medium recharge areas (11%) are identified in the Sassandra riverbed. The low recharge areas (14%) are found mainly in the West and North. The map of recharge areas is a decision-making tool that guides decision-makers in the identification of sectors likely to be the object of high-productivity boreholes, and also capable to be vulnerable to contaminants.[fr] La présente étude a pour objectif d’identifier et d’évaluer les zones potentielles de recharge des aquifères du Sud-Est de la Nawa par le couplage de l’analyse multicritère au radiocarbone en contexte de variabilité climatique. Elle est basée sur la combinaison d’informations spatiales relatives à différents paramètres (climat, topographie, sol, végétation, géologie, etc.) susceptibles d’influencer diversement la recharge. D’abord, la quantité d’eau infiltrée pour recharger les aquifères est estimée à partir du bilan hydrologique après caractérisation de la variabilité climatique à Soubré. Ensuite, les zones de recharge des aquifères fracturés sont cartographiées par analyse multicritère. Enfin, ces zones sont validées à partir des activités en carbone 14. De 1951 à 2017, le déficit pluviométrique de part et d’autre de la rupture de 1970 est de 14%. Deux périodes humides (1951-1970 et 1993-2017), intercalée d’une période sèche (1971-1992) caractérisent la zone d’étude. La lame d’eau estimée pour recharger les aquifères est de 243 mm de 1951 à 2017. La modélisation des paramètres climatique, topographique, pédologique, géologique, de la végétation, a permis d’élaborer des cartes thématiques bien structurées. Le croisement de celles-ci dans un SIG a facilité la conception de la carte des zones de recharge du Sud-Est de la Nawa. Cette carte met en évidence quatre zones d’aptitude à la recharge, validées par des activités en carbone 14. Les zones de recharge très forte (40%) et forte (35%) se localisent au Sud-Est et s’étendent jusqu’au Sud-Ouest de la zone d’étude. Les zones de recharge moyenne (11%) s’identifient dans le lit du Sassandra. Les zones de recharge faible (14%) occupent majoritairement l’Ouest et le Nord. La carte des zones de recharge est un outil d’aide à la décision qui oriente les décideurs dans l’identification des secteurs susceptibles de faire l’objet d’implantation de forages à forte productivité, et aussi susceptibles d’être vulnérables vis-à-vis des contaminants

Étude du potentiel de valorisation énergétique du biogaz de la décharge d’Akouédo (Abidjan, Côte d’Ivoire)

This study aims to evaluate the biogas production potential of the Akouédo landfill in Abidjan, Ivory Coast. Buried biodegradable organic waste generates biogas, which in particular contains methane, which is a greenhouse gas, but is also an alternative source of energy. An efficient capture of biogas thus makes it possible on the one hand to avoid diffuse emissions into the atmosphere and the associated impacts on the increase of the greenhouse effect, and on the other hand the energy recuperation of methane. Productivity measurements were made at the landfill site under static and intermittent pumping conditions. The results reveal a high biogas production potential composed of an average of 71.30 % v/v of methane and 27.10 % v/v of CO2. The monitoring carried out on the different wells of catchment suggests statistically a relatively uniform production on the whole of the site. However, many factors influence the production potential, including moisture and compaction of the waste mass, age and nature of waste, landfill methods, and so on. The valorization of methane must take into account these constraints for a faster amortization of the investment.Cette étude a pour objectif d’évaluer le potentiel de production de biogaz de la décharge d’Akouédo d’Abidjan en Côte d’Ivoire. Les déchets organiques biodégradables enfouis génèrent du biogaz contenant notamment du méthane qui est un gaz à effet de serre mais constitue également une source d’énergie alternative. Un captage efficace du biogaz permet donc d’une part d’éviter les émissions diffuses dans l’atmosphère et les impacts associés sur l’augmentation de l’effet de serre, et d’autre part la valorisation énergétique du méthane. Des mesures de productivité ont été réalisées sur le site de la décharge dans des conditions statiques et de pompage intermittents. Les résultats révèlent un potentiel élevé de production de biogaz composé en moyenne 71,30 % v/v de méthane et 27,10 % v/v de CO2. Les suivis réalisés sur les différents puits de captage suggèrent statistiquement une production relativement uniforme sur l’ensemble du site. Cependant, de nombreux facteurs influencent le potentiel de production, notamment l’humidité et la compaction du massif de déchets, l’âge et la nature des déchets, les méthodes d’enfouissement, etc. La valorisation du méthane doit prendre en compte ces contraintes pour un amortissement plus rapide de l’investissement

Télédétection radar, analyse statistique et multicritère appliquées à l’étude de la productivité en eau souterraine et de la vulnérabilité à la pollution des aquifères fissurés du département de Bongouanou, Côte d’Ivoire

Article publié en français (p. 49-61), avec un résumé étendu en anglais (p. 62-64) et 10 planches couleur hors-texte (p.85-94)International audienceExtended abstract:The Bongouanou Départment (administrative unit) is located in the humid tropical region of Ivory Coast (Plate 1), where agricultural and pastoral practices are very developed. In this region, the groundwater resource is much exploited. Although the situation is not alarming at this stage, it remains that the quantity and the quality of this resource should be carefully studied also in regards to the increase in diffused and point source pollution. To satisfy the water needs and to prevent the pollution risks, one approach is to improve our knowledge in the aquifers productivity and identify the vulnerable zones. It is for this purpose that this study has been initiated.The lithology is composed of volcano-sedimentary formations (80% of the territory), granitic intrusions (19%) and a small quaternary formation bordering the N'zi and Comoé rivers (Plate 2). Thus, the substratum consists almost entirely of schisteous and granitic basement, with, in its upper part, important indurated layers. There are therefore in this environment reservoirs of alterites and networks of cracks or fractures.To achieve groundwater availability assessment, we used two ENVISAT radar scenes of 12.5 m spatial resolution, VV polarization, from 26/02/2004 and 16/03/2004, taken by the Advanced Synthetic Aperture Radar (ASAR). Speckle filtering of radar images has been done using a Lee filter (Plate 3). Then image enhancement can show morphological discontinuities in the area (Plate 4).Drill parameter statistics provide insight into basement depth slices more productive in groundwater. Indicators designed for the study of spatial productivity are: accessibility and operability The criteria of definition of each indicator are recorded in table 1. The Arcview 3.3 software is a tool with full functionality for performing a multicriteria analysis thanks to its 'Interpolate grid' and 'Map calculator' functions of the 'Spatial Analyst' menu. Thus, at the end of the process, the four thematic classes of water productivity selected after aggregation are: bad, mediocre, good and excellent. From enhanced radar images, lineaments have been extracted and validated through comparison with photofractures derived from the photogeologic map of South-West region of Ivory Coast (Pate 5), and through ground checks. Finally, the fracturation map of Bongouanaou area has been obtained. This map (Plate 6) contains 2897 fractures, with 701 spacing measurements ranging from 0.234 m to 7.42 km for an area of 6670 km2. The fracture lengths range from 0.234 km to 21.23 km, with major fracture directions being: N-S and NW-SE. The cumulative length fracturing density map is shown in Plate 7.Calculations of average induced permeabilities show values ranging from 8.16-10-7 to 9.21-10-5 m.s-1, with an average of 0.91.10-5 m.s-1. A statistical study of average specific flow rates and average flow rates as a function of the total depth of the drilling was carried out and represented by the graphs in plate 8. On plate 8a it is found that the specific flow rates are low at depths less than 40 m and greater than 80 m, with values of less than 0.2 m2.h-1. At depth ranges between 40 and 80 m, the geometric mean specific flow rates are greater than 0.2 m2.h-1, with maxima of 0.57 m2.h-1 and 0.38 m2.h- 1 between 40 and 50 m and between 60 and 70 m. At the level of the average flow rates versus depths (Plate 8b), the depth range with high mean flows is between 40 and 80 m, with also maxima between 40 - 50 m and 70 - 80 m. Depth classes with high specific flows correspond to significant average flows. It can be remembered that in this basement the hydrodynamic characteristics (transmissivity, specific flow and permeability) are important between the depths between 40 and 80 m, with very sensitive peaks between 40 to 50 m and 60 to 70 m. Strong hydraulic properties at depths between 70 and 80 m are likely to be due to very deep fractures of tectonic origin.A study of the relationships between the specific flows and the exploitation rates is carried out and represented by the graph of plate 9. There is a strong correlation between the logarithmic values of these two parameters. The mathematical function describing this relationship is:Q / s = 0.089 Q 1.53with Q / s : specific flow rate (m2.h-1) Q: operating rate (m3.h-1) From this relationship, it is obvious that areas with high flows correspond to high hydraulic characteristics or high porosities. The potentially productive depth range in groundwater in this basement is therefore between 40 and 80 m, with a very remarkable peak in the 40 and 50 m interval. What are the regions concerned by these depths? On the accessibility map, North-West, South-West, North and Central-East, precisely the regions of Tiémelékro, Anoumaba, M'batto, Assié-Koumassi and Arrah offer good and excellent accessibility (plate 10). Regions of good and excellent exploitability also coincide with areas with high fracturing densities. Areas of good groundwater productivity generally provide significant flows at relatively shallow depths. Fractures and alteration affect the upper part of the substratum more than the deep part. A very high thickness of alteration (> 60 m thickness) tends to reduce the accessibility and the exploitability of the groundwater of the underlying fissured horizon (Plate 12).The development of the vulnerability map was done by calculating the vulnerability index using the DRASTIC method which integrates seven: the depth of the aquifer (D), the recharge or the effective infiltration (R), the lithology of the aquifer (A), the nature of the soil (S) , the topography or slope (T), the nature of the unsaturated zone (I) and the induced permeability (C). As the study environment is relatively homogeneous, the classification, coding and weighting of the criteria defining the vulnerability indicator are shown in table 2. The DRASTIC (IDRASTIC) indices obtained oscillate between 43 and 154. An approach developed in 1995 by the Quebec Ministry of Agriculture, Fisheries and Food consists of dividing the hydrogeological vulnerability scale into three or four major classes (see table 3).The calculation of the extreme percentages of vulnerability made it possible to obtain the following classification according to the ranges of vulnerability index:- 29% <IDRASTIC <30%, very low vulnerability;- 30% <IDRASTIC <45%, low vulnerability;- 45% <IDRASTIC <60%, medium vulnerability- 60% <IDRASTIC <65%, strong vulnerability.The vulnerability map for groundwater pollution in the Bongouanou region is thus obtained, integrating both the intrinsic and specific vulnerability factors and the precipitation for each hydrological catchment (Plate 13).In fact, the densely fractured sectors and weak slopes (plain zones) found in the south, the east, the west and the north are easily accessible and yield important flows even at small depths. Unfortunately, the DRASTIC method used to establish the pollution vulnerability map shows very strong indices in those regions. The boreholes productivity decreases from 70 m depth, most likely because a smaller frequency of fissures.Le département Bongouanou est situé dans la région tropicale humide de l’Est de la Côte d’Ivoire où la pratique agricole et pastorale est très développée. De plus, la ressource en eau souterraine est très exploitée à cause de la surpopulation. Bien que la situation ne soit pas encore alarmante dans cette région de socle, il n’en demeure pas moins que la quantité et la qualité de cette ressource sont sans cesse mises à l’épreuve, compte tenu de la croissance des sources de pollution, tant diffuses que ponctuelles. Pour satisfaire les besoins en eau et prévenir les risques de pollution, une des approches est la connaissance de sa productivité et l’identification des zones vulnérables. C’est dans ce but que cette étude a été initiée, en croisant l’analyse du réseau de fracturation détecté par les capteurs radar Envisat avec les paramètres de forage, avec des approches statistiques et d’analyse multicritères. Les résultats statistiques montrent que cet aquifère de socle a une productivité en eau souterraine modeste, avec un débit maximum de 21 m3.h-1 et une moyenne de 4,34 m3.h-1. La tranche de profondeur très productive en eau est comprise entre 40 et 80 m. Les cartes d’accessibilité et d’exploitabilité établies par analyse multicritère des facteurs (probabilité de succès des forages, profondeur d’extraction, niveau piézométrique et débits d’exploitation) mettent en évidence les zones très productives. En effet, les secteurs très fracturés et de faibles pentes (zone de plaine) tels que le Sud, l’Est, l’Ouest et le Nord, ont des ressources facilement accessibles et fournissent des débits importants à faibles profondeurs. Toutefois, la méthode DRASTIC, utilisée pour réaliser la carte de vulnérabilité à la pollution, montre des indices très élevés dans ces régions

: Contribution of multi-source data to the knowledge of the hydrographic network of the N'zi watershed (Ivory Coast)

Article publié e français (p. 33-45), avec un résumé étendu en anglais (p. 46-47) et 6 planches couleur hors-texte (p. 74-79)International audienceThe analysis of the hydrographic network supplies several informations that one must know for better watershed management. The N’zi watershed is located in Ivory Coast between longitudes 3°49’ and 5°22’ West and latitudes 6°00’ and 9°26’ North. It extends to 35,500 km2 and its main river is the N’zi of a length of 725 km which is fed by many tributaries. Two different and complementary approaches are used to characterize the hydrographic network of the N’zi watershed. The first approach refers to the development of a methodology of Landsat 7 ETM+ image processing in order to highlight the basic drainage patterns of the N’zi watershed. First, Landsat 7 ETM+ images undergo preliminary treatment (mosaic of the 6 scenes of Landsat 7 ETM+, windows and extraction of the N’zi watershed). Then, resulting images are submitted to the digital processing (various operations of enhancement, combinations of bands, filtering specifically that carried out by the 7×7 matrix of Sobel). Finally, transformed images undergo a visual analysis for the morphological identification of the hydrographic network of the N’zi watershed. The second approach refers to the global hydrographic network processing extracted of the topographical map and which constitutes a reliable source of validated information of grounds. This one is used as network of reference for the recognition of the tracing of the rivers on the images. The hydrographic network is used for the statistical analysis and for mapping the drainage density and also the functioning zones of the N’zi watershed.The hydrographic network is firstly discretized in regular meshes of 5 km side using Linwin 2.0 software. In each mesh, the total number of drains and the cumulated lengths of the drains are determined. These two parameters are compiled in a circular histogram in order to discriminate them on the basis of their orientation. A correlation is determined between the number of drains and the cumulated lengths of the drains. From the cumulated lengths of the drains by mesh, an interpolation by kriging of these values is carried out under ArcGis 10 to generate the drainage density map. The global hydrographic network of the N’zi watershed is organized into a hierarchy according to the convention of STRAHLER (1968) because of its geomorphological significance. A counting of all the drains according to their order is also carried out. A graph showing the number of drains according to the orders of the rivers is established in order to highlight the mathematical law governing the distribution of the drains. Finally, the hierarchical hydrographic network is used for the establishment of the iso-orders curves. The junctions of the drains which have the same order (1, 2,….. n) on the N’zi watershed are joined by the curves of respective iso-orders 1, 2,……. n. On the basis of geomorphological analysis of the N’zi watershed, relatively three distinct functioning zones are mapped.The analysis of the satellite images and the interpretation of the hydrographic network allowed to highlight the basic drainage patterns: dendritic, subdendritic, parallel and radial. The compared analysis of the drains in number and cumulated lengths shows that major directional class N90-100 is the longest. The number of drains is moderately correlated with the cumulated lengths of the drains of the N’zi watershed. The essential of the drainage of the N’zi watershed is assured by tributaries of small orders (1 and 2) with the order 1 which accounts for 77%. The drains of the hydrographic network fit better to the exponential law. The drainage density is variable on the N’zi watershed. The N’zi watershed is order 6. Five iso-orders curves are highlighted on this one. It is possible to map three distinct functioning zones on the N’zi watershed.- the recharge zone: it corresponds to geographical place occupied generally by the rivers of order 1 and 2. It is generally the zone of plateau where the principal rivers and their tributaries begin. - the zone with potential flow: it is occupied by rivers of order 3 and 4 and represents the sloping ground of the watershed. Water is very turbulent there.- the zone of fluvial flood risk is the area of rivers of order 5 and 6 and the confluence zones from which they result. It is a zone of reception and accumulation of waters draining the watershed. Indeed, the contribution in water of the tributaries of the N’zi is not negligible and contributes to an increase in the flow of this one in the confluence zones. Thus, these areas are more susceptible to flood risks.The mapping of the flood area is an essential tool not only for the prevention of the flood risks, but also for the management, planning and management of hydro-systems and for the future programming of the intervention areas.Les prises d’eau du N’zi entraînent des baisses drastiques de son régime, mettant ainsi en péril le processus de développement agricole. L’objectif de cette étude est de caractériser le réseau hydrographique du bassin versant du N’zi en vue de sa connaissance. La méthodologie consiste au développement de traitements numériques appropriés des images ETM+ de Landsat 7 et du réseau hydrographique extrait de la mosaïque des cartes topographiques. Le bassin versant du N’zi est caractérisé par des patrons de drainage de type dendritique à sub-dendritique, parallèle à radial. Il est d’ordre 6, avec les drains d’ordre 1 les plus représentatifs (77%). Ceux de direction N90-100 constitue la classe majoritaire et la plus dominante. Les drains s’ajustent mieux à la loi exponentielle. Le bassin versant du N’zi, avec un potentiel de drainage variable, est caractérisé par une zone d’alimentation, une zone à potentiel de flux et une zone à risque d’inondation fluviale. Cette dernière correspond aux cours d’eau d’ordre 5 et 6 et des confluences dont ils résultent

Etude dynamique des formations vegetales du departement de M’bahiakro, region preforestiere du centre-est de la Côte d’Ivoire par teledetection

L’objectif de ce travail est la cartographie de l’évolution spatio-temporelle des types de formation végétale dans le département de M’bahiakro, situé au centre-est de la Côte d’Ivoire, à partir des données de télédétection (images Landsat TM et ETM+) sur une période de 23 ans (1988-2011). Des traitements d’images par des calculs de l’indice de végétation normalisé, l’indice de brillance des sols, l’indice cuirassement et des rapports des bandes, intégrées dans des compositions colorées, ont permis de rehausser ces principaux types de formation végétale dans cette région préforestière. Une analyse diachronique des données satellitaires a été réalisée et l’approche de la classification supervisée, à partir des compositions colorées des bandes, a été retenue, en vue de la discrimination et le calcul des superficies de ces trois classes. Les précisions globales obtenues pour les images classifiées sont de 99,0264% (1988) et de 99,2775% (2011). Les coefficients Kappa sont de 0,9751% (1988) et 0,9873 % (2011) ; cela signifie que les classifications supervisées ont été parfaites. Ainsi, ont été identifiées les grands ensembles de formations végétales suivantes : la mosaïque forêt (claire, galerie), de jachère et de plantations, la savane arborée humide et la savane arbustive dans ce département de superficie 2561 Km2. En effet, en 1988 la classe mosaïque forêt (galerie, claire), de jachère et de plantations était estimée à 1692,5649 km2, soit une proportion de 66,9%, mais en 2011, cette superficie est réduite à 1250,2802 Km2, avec une nouvelle proportion de 48,82%. Il y a eu donc une transformation de 442,2847 Km2 de zones forestières en savane arborée et arbustive, soit une proportion de 17,17%. Ainsi, la savane arborée humide qui avait une superficie de 524,7489 Km2 en 1988, a obtenu en 2011, une superficie de 698,1286 Km2. De même, en 1988, la savane arbustive avait une superficie de 343,6862 Km2, cette superficie a augmentée de 269,2511 Km2. Cette régression de la zone forestière (forêts claires et galeries) est due aux fortes pressions anthropiques (feux de brousse, déforestation et exploitation du bois) et au phénomène du changement climatique, notamment la baisse de la pluviométrie et les longues saisons sèches dans cette localité depuis 1970.Mot clés: Télédétection, zone préforestière, déforestation, centre-est, Côte d’IvoireEnglish Title: Dynamic study of the vegetables formations from M’bahiakro department, preforest region of center-earst of Côte d’Ivoire by remote sensingEnglish AbstractThe objective of this work is to cartography the evolution of spatio-time of the fellow of vegetable formation in M’bahiakro department, situed in center-earst of Côte d’Ivoire, with the remong sensing data (images Landsat TM and ETM+) on 23 period (1988 - 2011). The images treatment by the calculation of the normalized vegetation index (NDVI), the brightness, the cuirasssement index and the bande (strip) division, integrated in colored composition have allowed to set of the principal fellow of vegetable formation in this preforest region. The diachronic analysis of satellite data has been realized and the supervised classification approach, from the colored composition of the bands (strip) has been used, in sight of the discrimination and the calculation of the areas of those three class. The global precisions obtained for the classified images are to 99.0264% (1988) and to 99.277% (2011). The Kappa coefficient are to 0.9751% (1988) and to 0.9873% (2011); it means that, the supervised classification have been perfect. In this way, have been identified, the big set of vegetable formation following: the mosaic forest (clear, gallery), fallow and plantation, the humid tree savanna and the shrub savanna in this department of 2561 Km2 areas. In fact, at 1988 the mosaic forest (clear, gallery), fallow and plantation had esteemed at 1692.5649 Km2, that is 66,9 % proportion, but at 2011, this area is reduced to 1250,2802 Km2, with a new proportion of 48.82%. It has been so a transformation of 442.284 Km2 of forest zones from tree and shrub savanna,that is 17.17% proportion. In this way, the humid tree savanna zone which have 524.7489 Km2 areas in 1988, has obtained in 2011, 698.1286 Km2 area. Likewise at 1988, the shrub savanna had area of 343.6862 Km2, this area has increased of 269.2511 Km2. This regression of the forest zone (clear and gallery) is owed to the strong anthropogenic pressure (fire of bush, degradation of the forest and the exploitation of the tree) and the phenomenon of climatic changeable, notably the fall of the rain and the length dry season in this locality.Keywords: Remote sensing, preforest zone, deforestation, center-earst, Côte d’Ivoir

Geochemical processes in the groundwater of Soubré, Ivory Coast, West Africa: Evidence from <SUP>14</SUP>C, <SUP>13</SUP>C, <SUP>18</SUP>O, <SUP>2</SUP>H and major ions

International audienceCharacteristics of the bedrock groundwater in the southwestern (SW) Ivory Coast (IC) (5-6°N, 4-7°W) are geochemically less known compared to those in the eastern part of the country. Several main cash crops, such as cocoa, coffee, rubber and palm oil, started being grown in this area twenty years ago because of the migration of agricultural activities from the East to the West of IC; this migration of agricultural activites was tied to climate variability. Within these large land use areas, food crops such as plantain bananas, yams, rice, maize, and vegetables are also grown. In this work, the mineralisation and groundwater pollution from East IC to West IC are studied within groundwater of the Archean and Paleoproterozoïce bedrock aquifers located in the SW IC. Stable isotopes ratios (δ18O, δ2H and δ13C), radiocarbon activity (A14C) and chemical contents (major ions) were measured on a set of 23 groundwater samples. In SW IC, the residence times calculated by an exponential mixing model (EMM) and a dispersion model (DM) with Dispersion Parameter values of 0.05 and 0.5 reveal that the oldest groundwater is located in the aquifer of migmatitic and granulitic gneiss (MiGn aquifer). Recent groundwater is located in the metagranitoid (MetGr) and the metasedimentary rocks (MetSe) aquifers. The most appropriate model to compute residence times is EMM because of the highest proportion of recharge in accordance with the nitrate content in groundwater after 1958, the beginning of Ivorian deforestation. However, this model lead to an overestimate of the residence time of groundwater particularly high in NO3. The oldest age of MiGn groundwater according to EMM calculation is ∼5 ka BP. The MiGn aquifer is less renewed (mean annual renewal rate of 0.03%) followed by those of MetSe (∼2.5 ka BP) and MetGr (∼2 ka BP), with mean annual renewal rates of 0.09% and 0.012%, respectively. Groundwater mineralisation is mainly governed by the hydrolysis of Al-silicates minerals and cultivation practice linked to K and N-fertilisers use, which leads to an increase of Ca, Mg and Na content. The values of TDS ranged from 49.4 to 720.4 mg L-1, which indicates the chemical characteristics of fresh water in SW IC. Most of the studied area groundwater are evaporated, likely due to both climate variability since the last 5 ka BP, delayed infiltration of rainwater which would be caused by impervious sediments covering the hard rock aquifers and agricultural practices affecting the most recently recharged groundwater. River water recharge from irrigation in cultivated areas may be possible. The groundwater with low 14C activities (64.33 pMC) has high residence times and is depleted in 13C content, while that with high 14C activities (99.58 pMC) is enriched in 13C content. This demonstrates that vegetation cover changed from C3 plants or forest (-23.9‰) to C4 plants, savannah or cultivation plants (-12.5‰) similar to those found in the southeastern IC