Caractérisation hydrogéochimique des eaux souterraines du département de Man (Ouest de la Côte d’Ivoire)

Cette étude avait pour but de comprendre le fonctionnement hydrogéochimique des eaux souterraines du département de Man situé à l’Ouest de la Côte d’Ivoire. Elle a fait appel aux méthodes de statistique descriptive, hydrochimique (diagramme de Piper) et à l’analyse en Composantes Principales (ACP) pour connaître la qualité, les faciès chimiques et les phénomènes de la minéralisation des eaux souterraines. L’échantillonnage a concerné 19 forages et les paramètres chimiques analysés sont Ca2+, Mg2+, Na+, K+, NH4+, SO42- , HCO3- , NO3-, Cl-, NO2- , Cu2+, Fe2+, PO43- et Al3. Les résultats de la statistique descriptive ont montré que les eaux avaient une température moyenne de 27,34°C en saison sèche et 28,005°C en saison pluvieuse. Les eaux étaient acides pendant les deux saisons. Les valeurs de pH étaient comprises entre 5,58 et 7,74 avec une moyenne de 6,673±0,541 en saison sèche et entre 5,25 et 7,11 avec une moyenne de 6,223±0,441 en saison pluvieuse. Elles étaient peu minéralisées, avec des moyennes de conductivité électrique de 219,51 μS/cm en saison sèche et 206,50 μS/cm en saison pluvieuse. Ces eaux présentaient un faciès bicarbonaté calcique et magnésien majoritaire (Ca-Mg- HCO3), un faciès chloruré calcique et magnésien (Ca-Mg-Cl) au cours des deux saisons et un faciès bicarbonaté sodique et potassique en saison pluvieuse (Na-K-HCO3). Les principaux phénomènes à l’origine de la minéralisation des eaux étaient la minéralisation-temps de séjour, l’apport superficiel et la dégradation anthropique de la qualité des eaux et la pollution organique. Ces résultats constituent une base de données dans la gestion des eaux souterraines de la région

Assessment of Wells Water Quality and their Suitability for Drinking in M'Bahiakro City (Côte d'Ivoire)

The present study was carried out to assess the quality and the suitability of the well waters for drinking in M’bahiakro city (centre-east of Côte d’Ivoire). The work was performed on 71 wells in February 2012 (dry season) and June 2012 (rainy season). Groundwater levels and physico-chemical parameters (pH, temperature, electrical conductivity, redox potential (Eh), Total Dissolved Solid (TDS) and Salinity) were measured to assess the water table fluctuation and the groundwater quality. Standardized Principal Component Analysis (SPCA) was calculated to group the well waters and to evaluate their suitability for drinking according to different classes. Water table varies between 125 and 135 m during the dry season and between 127 and 136 m during the rainy season with a West-Est flow direction. The recharge values ranged between 0.57 m and 5.57 m. Wells waters are generally acidic (pH<6.5), high mineralized with conductivities and Total Dissolved Solids (TDS) respectively above 600 µS/cm and 300 mg/l. Well water salinity values ranged between 0.30 and 0.5%. The Standardized Principal Component Analysis (SPCA) allowed distinguishing three important groups of water within M’bahiakro area: the first group of wells with high mineralized water, the second group of wells with high potential redox (Eh) and the third group of wells with pH closer to neutral. The first and second groups are not very suitable for drinking because they are suspected of being contaminated by anthropogenic sources such as septic tanks and wild dump. Waters of these wells need to be treated before any domestic use

Yam Cropping System in Cote d’Ivoire: Current Practices and Constraints

Yam is the first food crop in Côte d'Ivoire. It is being cultivated under a traditional technique system with low output. Detailed profiling of the current practices and opportunities for improvement is essential to increase the&nbsp;benefits of yam for food security and income in the country. This study diagnosed the current practices, constraints, and requirements in order to gain insight on the yam cropping system for research and development in Côte d'Ivoire. The surveys were conducted in seven (7) regions in the main yam production area. Groups of 60 producers per region were investigated. Individual surveys were also conducted on-farm, particularly for diagnosing the physical environment and yam-based production systems. As results, yambased production systems are characterized by mixed cropping (cassava, corn and vegetable crops) and/or rotation with various other crops (rice, groundnut, vegetable crops, …). Preferred plots for yam cultivation are forest, savannah or fallow areas. The major constraints in yam cultivation were the effects of environmental stresses, labor scarcity, pest damage, tuber and seed storage difficulties as well as the low market value of yam. The most cultivated yam varieties are Bètè-Bètè and Florido for Dioscorea alata and Lokpa for Dioscorea rotundata. The cropping system, the species and varieties vary according to the region, the topo sequence and the type of soil. Knowledgebuilding that take into account constraints related to yam cultivation, for each production area, can serve as guidance for variety breeding and cultivation environment redefinition

Development of a Model for Assessing Vulnerability to Pollution of Groundwater in Fissured Aquifers: The Case of the Ehania Watershed (South-Eastern C&#244;te d’Ivoire)

International audienceThe protection of aquifers is a major concern for the authorities, especially in areas where there are large agro-industrial exploitations. The objective of this study is to define a new method of aquifer protection based on the characteristics of the structures of aquifers. The intrinsic vulnerability mapping method, PaPRI was used. It is a variant of the PaPRIKa method applied in karstic environment which has been adapted for its application in basement environment. This method uses three factors, including aquifer protection (P), using the soil cover, the unsaturated zone and the thickness of the alteration layer, (R) for the rock type and (I) for infiltration which including slope and drainage density. PAPRI is a method based on the weighting of different factors. The results obtained show 4 classes that evolve from low vulnerability classes (5% of the study area) to high and very high vulnerability classes (58%) and average vulnerability classes (37%). The classes of high and very high vulnerability, which indicate the zones that are very exposed to pollution, are more present in the central-northern part of the study area, with a few appearances towards the south. These zones could be related to topography due to the often very high slopes observed in the area. One of the advantages of this new method lies in the characterization of the alterations that strongly influence the migration of pollutants towards the water tables according to their nature and their thickness

Dynamique forestière et pression urbaine dans le Parc national du Banco (Abidjan, Côte d’Ivoire)

Since 1960s, the Ivorian government care about his forest conservation. Thus, the Ivory Coast has set up a network of protected areas to conserve its forests and biodiversity. Located in Abidjan, the Banco National Park (PNB) and its periphery face a deeply environment changes in recent decades. This research aims to describe and analyze the various threats to urban pressure, including the risks of deforestation and pollution around and inside the PNB. To achieve these objectives, the analysis of the land cover and vegetation change help to understand the environmental dynamics of the Banco forest. The inventory and mapping of the types of risk and their impact on PNB enable to show the most vulnerable areas due to anthropogenic pressures and urbanization. The study of the types of human pressures in PNB is conducted through observations to detect spatial changes in recent years. The study also relies on an aerial photograph of 1955 and Spot satellite image taken in 1998. Aerial photography was acquired at the Centre of Cartography and Remote Sensing and the National Geographic Institute (IGN-Paris). The satellite image was obtained with the ISIS program of Spot Image. These data were used to map land cover in 1955 and 1998 and compare the evolution of the vegetation through a diachronic analysis.Indeed, in the year 1955, the land in the park and its periphery showed that the landscape was dominated by the forest despite the presence of a few urban space. The forest covered an area of 5462 ha while secondary forest covered an area of 9220 ha. These two types of forest represented nearly 90 % of the landscape of the study area. In 1998, 3450 ha of forest and 434 ha of forest plantations represente the vegetation of the PNB. Bordered by four towns, the Banco National Park suffers from the consequences of rapid urbanization. This rapid growth in the district of Abidjan has created many environmental problems, including the proliferation of shantytowns, inadequate facilities and transport infrastructure, sanitation and housing. The park is bordered to the north, east and south many poor neighborhoods without sanitation equipment. The PNB is to be the outlet for solid and liquid waste from households. Municipal storm water is discharged into the park. Multiple industrial units, informal activities and new residential areas bordering the park which is already facing since a decades to the creation of many facilities (creation of motorways, express roads, infrastructure and equipment necessary to meet demand of urban water, electricity etc..). In addition, many areas of PNB are subject to land claims, including the north-east and south of the park. These disputed areas are correlated with particular types of communities along the villages of Anonkoua Kouté Sagbé and north-Agban Attié and Agban-village southeast, and southwest Andokoi. In order to improve the protection of PNB and to enable his participation in economic development of people, its directors have established a policy of participatory management. This strategy involves local people in conservation. The association of local people in the community management of forest resources can empower them by involving them in monitoring missions, recovery and development. The development of the park through ecotourism, the development of alternative activities toward poachers and illegal loggers are among the many strategies implemented to save this threatened ecosystem. Ecotourism has become the most important policy of participatory management of public administrators of PNB

Dynamique forestière et pression urbaine dans le Parc national du Banco (Abidjan, Côte d’Ivoire)

La problématique de la conservation de la forêt ivoirienne et de ses ressources est au centre des préoccupations des pouvoirs publics depuis les années 1960. Ainsi, la Côte d’Ivoire a-t-elle mis en place un réseau d’aires protégées, notamment plusieurs parcs nationaux, pour conserver ses massifs forestiers et leurs biodiversités. Situé à Abidjan, le Parc National du Banco (PNB) et sa périphérie connaissent de profondes mutations environnementales depuis quelques décennies. Ces mutations liées principalement aux activités humaines et à l’urbanisation rapide du district d’Abidjan provoquent une dégradation du massif forestier du PNB. Cette recherche vise à décrire et à analyser les différentes menaces liées à la pression urbaine, notamment les risques de déforestation et de pollution qui exposent certaines zones du PNB. Pour atteindre ces objectifs, l’analyse de l’évolution de la végétation, des types d’occupation du sol, des recompositions territoriales et des jeux des différents acteurs est mise à profit pour comprendre les dynamiques environnementales de la forêt du Banco et sa périphérie. L’inventaire et la cartographie des types de risque ainsi que leurs impacts sur le PNB permettent d’identifier les zones les plus vulnérables aux pressions anthropiques et à l’urbanisation. L’étude des types de pressions humaines sur la forêt du PNB est menée à travers des observations de terrain pour détecter les changements spatiaux des dernières années. L’étude s’appuie également sur une photographie aérienne de 1955 et une image satellite Spot prise en 1998. La photographie aérienne a été acquise auprès du Centre de Cartographie et Télédétection (CCT-Abidjan) et de l’Institut Géographique National (IGN-Paris). L’image satellite a été obtenue grâce au programme ISIS de Spot Image. Ces données ont permis de cartographier l’occupation du sol en 1955 et 1998 et de comparer l’évolution de la végétation à travers une analyse diachronique.Les résultats de l’étude montrent que dans les années 1955, le paysage du PNB et sa périphérie était dominé par la forêt malgré la présence de quelques tâches urbaines. La forêt couvrait une superficie de 5462 ha tandis que la forêt secondaire occupait une surface de 9220 ha. Ces deux formations forestières représentaient près de 90 % du paysage de la zone d’étude. En 1998, 3450 ha de forêt et 434 ha de plantations forestières constituent la végétation du PNB. Bordé de quatre communes, le Parc National du Banco subit les conséquences de l’urbanisation galopante. Cette croissance rapide du district d’Abidjan a engendré de nombreux problèmes environnementaux, notamment la multiplication des quartiers précaires qui bordent le parc au nord, à l’est et au sud, l’insuffisance des équipements et infrastructures de transport, d’assainissement et de logement. Ainsi, le PNB est-il devenu l’exutoire des déchets solides et liquides des ménages abidjanais. Les eaux pluviales communales, notamment à Abobo au nord, Adjamé à l’est et Yopougon au sud sont également évacuées dans le parc. De multiples unités industrielles, des activités informelles et de nouveaux quartiers résidentiels bordent le PNB qui fait déjà face depuis des décennies aux aménagements divers (création d’autoroutes, de voies express, d’infrastructures et d’équipements nécessaires à la satisfaction de la demande urbaine en eau, électricité, etc.). En outre, de nombreuses zones du PNB font l’objet de revendications foncières, notamment le nord-est et le sud du parc. Ces zones contestées se situent dans les villages d’Anonkoua Kouté et de Sagbé au nord, Agban-attié et Agban-village au sud-est, et Andokoi au sud-ouest. Pour répondre aux problèmes liés à l’action des populations dans le PNB et sa périphérie, les gestionnaires ont mis en place une série de mesures alternatives pour améliorer sa conservation. En effet, dans le but de le protéger davantage et de le faire participer au développement économique des populations, ses administrateurs ont mis en place une politique de gestion participative. Cette stratégie permet d’associer les populations locales à sa conservation. L’association de celles-ci à cette gestion communautaire des ressources forestières permet de les responsabiliser en les impliquant dans les missions de surveillance, de valorisation et d’aménagement. La mise en valeur du parc notamment à travers l’écotourisme, le développement d’activités alternatives à l’attention des braconniers et des exploitants illégaux font également partie des nombreuses stratégies mises en place pour sauver cet écosystème menacé. L’écotourisme est ainsi devenu le fer de lance de la politique de gestion participative des administrateurs publics du PNB.Since 1960s, the Ivorian government care about his forest conservation. Thus, the Ivory Coast has set up a network of protected areas to conserve its forests and biodiversity. Located in Abidjan, the Banco National Park (PNB) and its periphery face a deeply environment changes in recent decades. This research aims to describe and analyze the various threats to urban pressure, including the risks of deforestation and pollution around and inside the PNB. To achieve these objectives, the analysis of the land cover and vegetation change help to understand the environmental dynamics of the Banco forest. The inventory and mapping of the types of risk and their impact on PNB enable to show the most vulnerable areas due to anthropogenic pressures and urbanization. The study of the types of human pressures in PNB is conducted through observations to detect spatial changes in recent years. The study also relies on an aerial photograph of 1955 and Spot satellite image taken in 1998. Aerial photography was acquired at the Centre of Cartography and Remote Sensing and the National Geographic Institute (IGN-Paris). The satellite image was obtained with the ISIS program of Spot Image. These data were used to map land cover in 1955 and 1998 and compare the evolution of the vegetation through a diachronic analysis.Indeed, in the year 1955, the land in the park and its periphery showed that the landscape was dominated by the forest despite the presence of a few urban space. The forest covered an area of 5462 ha while secondary forest covered an area of 9220 ha. These two types of forest represented nearly 90 % of the landscape of the study area. In 1998, 3450 ha of forest and 434 ha of forest plantations represente the vegetation of the PNB. Bordered by four towns, the Banco National Park suffers from the consequences of rapid urbanization. This rapid growth in the district of Abidjan has created many environmental problems, including the proliferation of shantytowns, inadequate facilities and transport infrastructure, sanitation and housing. The park is bordered to the north, east and south many poor neighborhoods without sanitation equipment. The PNB is to be the outlet for solid and liquid waste from households. Municipal storm water is discharged into the park. Multiple industrial units, informal activities and new residential areas bordering the park which is already facing since a decades to the creation of many facilities (creation of motorways, express roads, infrastructure and equipment necessary to meet demand of urban water, electricity etc..). In addition, many areas of PNB are subject to land claims, including the north-east and south of the park. These disputed areas are correlated with particular types of communities along the villages of Anonkoua Kouté Sagbé and north-Agban Attié and Agban-village southeast, and southwest Andokoi. In order to improve the protection of PNB and to enable his participation in economic development of people, its directors have established a policy of participatory management. This strategy involves local people in conservation. The association of local people in the community management of forest resources can empower them by involving them in monitoring missions, recovery and development. The development of the park through ecotourism, the development of alternative activities toward poachers and illegal loggers are among the many strategies implemented to save this threatened ecosystem. Ecotourism has become the most important policy of participatory management of public administrators of PNB

Dynamique forestière et pression urbaine dans le Parc national du Banco (Abidjan, Côte d’Ivoire)

Since 1960s, the Ivorian government care about his forest conservation. Thus, the Ivory Coast has set up a network of protected areas to conserve its forests and biodiversity. Located in Abidjan, the Banco National Park (PNB) and its periphery face a deeply environment changes in recent decades. This research aims to describe and analyze the various threats to urban pressure, including the risks of deforestation and pollution around and inside the PNB. To achieve these objectives, the analysis of the land cover and vegetation change help to understand the environmental dynamics of the Banco forest. The inventory and mapping of the types of risk and their impact on PNB enable to show the most vulnerable areas due to anthropogenic pressures and urbanization. The study of the types of human pressures in PNB is conducted through observations to detect spatial changes in recent years. The study also relies on an aerial photograph of 1955 and Spot satellite image taken in 1998. Aerial photography was acquired at the Centre of Cartography and Remote Sensing and the National Geographic Institute (IGN-Paris). The satellite image was obtained with the ISIS program of Spot Image. These data were used to map land cover in 1955 and 1998 and compare the evolution of the vegetation through a diachronic analysis.Indeed, in the year 1955, the land in the park and its periphery showed that the landscape was dominated by the forest despite the presence of a few urban space. The forest covered an area of 5462 ha while secondary forest covered an area of 9220 ha. These two types of forest represented nearly 90 % of the landscape of the study area. In 1998, 3450 ha of forest and 434 ha of forest plantations represente the vegetation of the PNB. Bordered by four towns, the Banco National Park suffers from the consequences of rapid urbanization. This rapid growth in the district of Abidjan has created many environmental problems, including the proliferation of shantytowns, inadequate facilities and transport infrastructure, sanitation and housing. The park is bordered to the north, east and south many poor neighborhoods without sanitation equipment. The PNB is to be the outlet for solid and liquid waste from households. Municipal storm water is discharged into the park. Multiple industrial units, informal activities and new residential areas bordering the park which is already facing since a decades to the creation of many facilities (creation of motorways, express roads, infrastructure and equipment necessary to meet demand of urban water, electricity etc..). In addition, many areas of PNB are subject to land claims, including the north-east and south of the park. These disputed areas are correlated with particular types of communities along the villages of Anonkoua Kouté Sagbé and north-Agban Attié and Agban-village southeast, and southwest Andokoi. In order to improve the protection of PNB and to enable his participation in economic development of people, its directors have established a policy of participatory management. This strategy involves local people in conservation. The association of local people in the community management of forest resources can empower them by involving them in monitoring missions, recovery and development. The development of the park through ecotourism, the development of alternative activities toward poachers and illegal loggers are among the many strategies implemented to save this threatened ecosystem. Ecotourism has become the most important policy of participatory management of public administrators of PNB

Study of Groundwater-river Interactions Using Hydrochemical Tracers in Fissured Rock: Case of the Lobo Watershed at Nibéhibé (Central-West, Côte d’Ivoire)

Water is a vital resource for all populations. However, there are warning signs that the water from the Lobo River used by SODECI to supply drinking water to the population is declining in quantity during the dry season and its quality is becoming poor due to climate variability and anthropogenic activities. However, the river is able to maintain a certain flow, probably with the contribution of groundwater. It is therefore a question of whether there is really a connection between surface water and groundwater. The aim of this study is to characterize the groundwater-river interactions based on the physico-chemical parameters of the Lobo watershed in Nibéhibé. The approach adopted is a coupled statistical-geochemical approach applied on data from two sampling campaigns (dry and rainy season). This coupled approach consisted, on the one hand, in understanding the chemical specificities within the water classes using the piper diagram and, on the other hand, in classifying the waters according to their physico-chemical similarity and highlighting the phenomena at the origin of the water mineralization using the Kohonen self-organized map (SOM). The results obtained from the piper diagram show that in both the wet and dry seasons, the chemical signature of the waters remains controlled by two main hydrochemical facies: the chlorinated calcium-magnesium nitrate hydrofacies and the bicarbonate calcium-magnesium hydrofacies. Kohonen's self-organized map has established that the mineralization of groundwater, under natural conditions, comes from the nature of the rocks crossed during infiltration and from the contact time between water and minerals. This work provides managers with decision-support tools for planning and searching for groundwater in support of surface water to reinforce the drinking water supply of the populations in this watershed.&nbsp

Spatio-temporal characterization of the physico-chemical quality of groundwater: Case of the Lobo watershed (Centre-west of Côte d'Ivoire)

International audienc