Comparative Analysis Of The Mapping Of The Vulnerability To Pollution Of Fissured Aquifers In Agboville Department By Drastic And SI Methods (South-East Of Côte d'Ivoire)

The study aims to establish vulnerability maps of groundwater pollution in Agboville department due to anthropogenic pressures, with a view to their sustainable management. The methods used are DRASTIC and SI. They use four common vulnerability parameters (groundwater depth, recharge, aquifer materials and topography) that are intrinsic to the aquifer. To these parameters, the DRASTIC method associates three others (soil type, unsaturated zone and hydraulic conductivity), while the SI method associates a fifth extrinsic parameter (land use). Their thematic mapping, followed by their combination in a GIS, made it possible to draw up the various pollution vulnerability maps using both methods. Each map highlights five classes of vulnerability. The dominant vulnerability classes in terms of surface area occupied are: low (32%) and high (36%) for the DRASTIC method, and medium (42%) and high (26%) for the SI method. The superimposition of the map of spatial distribution of nitrate levels in groundwater with the established vulnerability maps shows that the areas with low levels coincide with the low vulnerability classes, thus allowing their validation. The results of the Kappa test and the surface analysis to examine the vulnerability maps reveal that the Kappa coefficient (K = 0.29) is reliable and gave a fair agreement between the two methods. This agreement is confirmed by the surface analysis (45,25 %). The SI method appears to be the most appropriate for assessing the vulnerability to groundwater pollution in this area

Analyse comparative entre la distribution des fréquences de conductivité électrique et les faciès géochimiques des eaux des aquifères de socle (Côte d’Ivoire)

La conductivité électrique est un indicateur de la minéralisation totale des eaux et son étude permet de faire un suivi hydrochimique des systèmes hydrologiques. L'objectif de ce travail est d’analyser l’apport de l’étude de la distribution des fréquences de conductivité électrique à la caractérisation géochimique des eaux des aquifères fissurés de socle cristallin et cristallophyllien. Les zones tests utilisées dans le cadre de ce travail appartiennent au socle ivoirien. La méthodologie adoptée est basée d’une part sur l’étude des courbes de fréquence de conductivité électrique. D’autre part, les faciès chimiques des eaux souterraines ont été déterminés à partir du diagramme de Piper. L’analyse de la distribution des fréquences de conductivité électrique a fait ressortir diverses familles d’eau. La projection des échantillons d’eau sur le diagramme de Piper a permis de mettre en évidence plusieurs faciès des eaux souterraines. La comparaison des différents résultats met en évidence une concordance au niveau de quatre échantillons (Bondoukou, Tiassalé, ex-N’zi- Comoé et Tiébissou-Didievi) et une non concordance au niveau de deux échantillons (Guiglo-Duekoué et Agboville). On peut conclure que l’analyse des fréquences de conductivité électrique permet en général de confirmer les différents faciès hydrogéochimiques.© 2016 International Formulae Group. All rights reserved.Mots clés: Hydrogéochimie, conductivité électrique, diagramme de Piper, socle cristallin et cristallophyllien, Côte d’IvoireEnglish Title: Comparative analysis of electrical conductivity frequencies distribution and geochemical facies of hard rock aquifers waters (Ivory Coast)English AbstractElectrical conductivity is a measure of the total mineralization of the water and its study allows for a hydrochemical monitoring of water systems. The objective of this work was to analyze the contribution of the  study of electrical conductivity frequencies distribution to the geochemical characterization of the hard rock aquifers waters. The test zones used in the context of this work belong to the Ivorian hard rock aquifers. The methodology is based firstly on the study of the frequency curves of the electrical conductivity. On the other hand, chemical facies of groundwater have been determined from the Piper diagram. The analysis of the distribution of the electrical conductivity of frequencies has highlighted various water families. The projection of water samples on the Piper diagram helped highlight several facies of groundwater. Comparing the results of different methodological approaches reveals a match in four samples (Bondoukou, Tiassalé, N'zi-Comoé and Tiébissou-Didievi) and a mismatch in two samples (Guiglo-Duékoué and Agboville). Given concordances results in most cases, we can say that the analysis of the electrical conductivity of frequencies generally allows confirming the different hydrogeochemical facies in the hard rock aquifers.© 2016 International Formulae Group. All rights reserved.Keywords: Hydrogeochemistry, electrical conductivity, Piper diagram, hard rock aquifers, Ivory Coas

Impact of Climate Variabilty on Water Resources And Population Health in the South Eastern Coastal Area of Côte d’Ivoire

The present study evaluates the impact of climate variability on water resources and population health in the coastal area of Cote d’Ivoire between Abidjan and Aboisso. First, hydroclimatic methods (Nicholson index) and statistical tests (Pettitt test, Hubert segmentation) were used for variability characterisation. Then, Thornthwaite Water balance method was used to evaluate water availability for aquifers recharge. Coefficient depletion method was also used to assess the impact of climate variability on surface water resources. The relationship between diseases occurence (AhigbeKoffikro and Samo) and rainfall pattern was evaluated through descriptive method. The results revealed important fluctuations of water resources levels at that time. The relationship rainfall-runoff showed with synchron trend that rivers flows regime was linked to rainfall. The impact on groundwater resources was explained by deficit of infiltrated water of about 35.49% and 22.61% after 1982 break at Abidjan airport and Bingerville stations respectively. Concerning health, 63% of malaria cases was observed against 2.85% for diarrhoea and 2.35% for helminthiasis. There was a strong relationship between rainfall and the diseases (malaria and diarrhoea)

Landsat 8 Oli Satellite Imagery Mapping and Analysis of Bedrock Fracture Networks in the Departments of Yamoussoukro and Toumodi (Central Cote d’Ivoire)

This study focuses on the departments of Yamoussoukro and Toumodi located in central Côte d'Ivoire where the problem of drinking water supply is a growing reality. Its objective is to map and analyze the fracturing likely to develop underground aquifers from Landsat 8 OLI data. The set of techniques (color composition, directional and gradient filters) used resulted in the enhancement of linear structures present on satellite images, allowing a better mapping of geological features. The linear map obtained, after the different treatments, is very dense and includes 2063 lineaments. The validation of these different linear structures was made on the basis of the drillings already carried out, from the data of the geophysics. The analysis of the fracture networks has highlighted two dominant directions which are N0°-10° (N-S) and N90°-100° (E-W) highlighting the heterogeneity of the geological formations.  These results constitute an essential contribution to the exploitation of groundwater resources in the departments of Yamoussoukro and Toumodi

Modélisation Des Extrêmes Climlatiques De La Région De La Marahoué À Partir D’un Générateur Stochastique De Temps Mono-Site (Weagets)

L’objectif de ce travail est d’analyser et de modéliser les tendances pluviométriques extrêmes à l’horizon 2050 à partir des données pluviométriques journalières de 1980 à 2013. Ces données ont été analysées à l’aide du programme ClimPACT 2 master qui a servi de calcul des indices climatiques. Le modèle WEAGETS a été utilisé pour modéliser ces données hydroclimatiques à l’horizon 2050 à partir de la méthode des chaines de Markov d’ordre 3. Les résultats montrent que la moyenne des cumuls de pluies moyennes mensuels observés est de 103,97 mm et celle estimée est de 100,71 mm soit un déficit de 3,26 mm par rapport à celle observée au cours de la chronique d’étude. La précipitation totale maximale d’un jour pluvieux (Rx1day) observé et généré présente une allure décroissante dans la région avec des coefficients respectifs de -0,37 et -0,25. Au cours des périodes 2014 à 2024, les localités de Zuénoula et de Sinfra seront dominées par des séquences sèches qui seront également observées durant les périodes de 2038 à 2050 dans le Sud et le Centre de la zone d’étude. Les jours consécutivement secs (CDD) vont augmenter dans toute la Marahoué, tandis que les jours consécutivement humides (CWD) vont y baisser progressivement. Ces résultats serviront à la mise en place des stratégies d’adaptation des populations face à ce fléau. The objective of this work is to analyze and model extreme rainfall trends up to 2050 based on daily rainfall data from 1980 to 2013. These data were analysed using the ClimPACT 2 master program which was used to calculate the climate indices. The WEAGETS model was used to model these hydroclimatic data by 2050 using the Markov Chain 3 method. The results show that the average monthly average rainfall accumulation observed is 103.97 mm and the estimated average rainfall is 100.71 mm, representing a deficit of 3.26 mm compared to that observed during the study chronicle. The maximum total precipitation of a rainy day (Rx1day) observed and generated shows a decreasing rate in the region with respective coefficients of -0.37 and -0.25. During the periods 2014 to 2024, the localities of Zuénoula and Sinfra will be dominated by dry sequences which will also be observed during the periods 2038 to 2050 in the southern and central parts of the study area. Consecutively dry days (CDD) will increase throughout Marahoué, while consecutively wet days (CWD) will gradually decrease there. These results will be used to put in place strategies to help populations adapt to this scourge

Landsat 8 Oli Satellite Imagery Mapping and Analysis of Bedrock Fracture Networks in the Departments of Yamoussoukro and Toumodi (Central Cote d’Ivoire)

This study focuses on the departments of Yamoussoukro and Toumodi located in central Côte d'Ivoire where the problem of drinking water supply is a growing reality. Its objective is to map and analyze the fracturing likely to develop underground aquifers from Landsat 8 OLI data. The set of techniques (color composition, directional and gradient filters) used resulted in the enhancement of linear structures present on satellite images, allowing a better mapping of geological features. The linear map obtained, after the different treatments, is very dense and includes 2063 lineaments. The validation of these different linear structures was made on the basis of the drillings already carried out, from the data of the geophysics. The analysis of the fracture networks has highlighted two dominant directions which are N0°-10° (N-S) and N90°-100° (E-W) highlighting the heterogeneity of the geological formations.  These results constitute an essential contribution to the exploitation of groundwater resources in the departments of Yamoussoukro and Toumodi

Variabilite Des Extremes Pluviometriques Sur Le Bassin Versant De La Riviere Bia (Sud-Est, Cote d’Ivoire)

Climate change is a reality which affects many climatic variables, including precipitation. The objective of this article is to study the extreme rain variability from a historical database (1941 - 2000). For this purpose, eleven (11) rainfall indices were calculated at the Adiaké, Bianouan, Ayamé, and Agnibilekro rainfall stations in Côte d'Ivoire. Due to lack of data on daily rainfall on the Ghanaian section of watershed, nine (9) monthly precipitations indices were estimated from monthly rainfall at the Enshi and Buakuc stations. The trend analysis of the precipitations indices show that a generalized downward was most significant in Adiaké compared to other stations. Furthermore, indices extreme thresholding (P99, P99p, P99,5 and P99,5p) have experienced a stable trend and a stationary evolution. All steps were detected in the non-stationary indices mostly observed after 1980 (late break) and before 1960 (precocious break)

CARTOGRAPHIE DES ZONES A RISQUE DINONDATION PAR DEBORDEMENT DES COURS DEAU DANS LA REGION SEMI-MONTAGNEUSE DE MAN : APPROCHE PAR TELEDETECTION ET ANALYSE MULTICRITERE

The semi-mountainous region of Man has been affected by recurrent flooding, linked to overflowing waters, since the 2010s in connexion with climatic variability. Numerous material and human damages are linked to these floods. Face to this, this studys aim was to map areas at risk of overflow flooding in the region, with a view to helping manage these floods. Methods used include remote sensing, Geographic Information Systems and multi-criteria analysis. Factors taken into account are rainfall, topography, drainage density and soil types for the hazard, and land-use entities and population exposure for vulnerability. All these factors were mapped using satellite images and soil, demographic and field data. Thematic maps were weighted, standardized and integrated into the GIS on the basis of multi-criteria analysis. Obtained results are hazard, vulnerability and risk maps. These maps were validated by the identification and geolocation of flood-related land features. High-hazard, high-vulnerability and high-risk zones represent 36.56%, 42,39% and 33,94% of the region respectively. High-risk zones cover around 75%, 50% and 30% of the Danane, Man and Logouale departments respectively. Knowledge of these at-risk areas is an asset for decision-makers in choosing priority actions to be taken against flooding

Study of physical and chemical quality of waters of an anthropised tropical lagoon : Case of the aghien lagoon (South-East of Côte d’Ivoire)

The problem of drinking water supply in Abidjan Autonomous District is acute. The objective of this study is to assess the quality of Aghien Lagoon waters with a view to their use to make up drinking water deficit. To do this, French Association of Standardization methods were used for determination of various parameters of 48 samples of lagoon waters. Piper diagram was used for waters hydrochemical classification, as well as Principal Component Analysis (PCA) for determining the processes responsible for their mineralization. The mean values of the physical and chemical parameters (pH, Ca2+, K+, Cl-, Na+, Mg2+, PO43-, SO42-, CE, TDS, DBO5, NO3-, NO2-, Cd, Pb, Zn and Cu) comply with the French values required for surface fresh waters intended for drinking water production.On the other hand, mean concentrations of NH4 + (36.88 mg / L) and Fe (1834.48 μg / L) and turbidity (14.98 NTU) are higher than these regulatory limits. Aghien lagoon waters consist of 54.55% of chlorinated water and 45.45% of bicarbonate water. The chemistry of these waters is controlled by rainfull, the weathering from rocks of the watershed, decomposition of organic matter, fertilizers from agricultural activities, and the weathering of silicate minerals from the underlying sediments. The latter seems to play a minor role in hydrochemistry, due to the relatively short residence time.On the whole, Aghien Lagoon waters could be used for the production of drinking water