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Statistical analysis of a borehole database, linear discharges, and water strikes processing enabled an understanding of the structure, geometry and hydrodynamic properties of the metamorphic hard rock aquifers from the Montagnes District, Western Côte d’Ivoire. The database comprises 1654 boreholes among which 445 only were usable for this research work after its pre-processing. Analysis shows that the structure of the aquifer is similar to that observed in several other areas in the world: it developed due to weathering processes, comprises the capacitive saprolite, 10–20 m thick on average, and an underlying transmissive fractured layer, overlying the unweathered impermeable hard rock. The fractured layer is 80 m thick, the first 40 to 45 metres being its most productive zone, with a 11.3 m3/h median productivity. This research shows that metamorphic aquifers exhibit similar aquifer properties (thickness, hydrodynamic parameters) as plutonic ones and that there is interest in using such databases for research and other purposes. However, a rigorous pre-treatment of the data is mandatory, and geological data from published maps must be used instead of the geological data from the database. A previous methodology aiming at processing the boreholes’ linear discharges was improved. It notably appears that the slope method must be preferred to the percentile method.

Rainwater pollution in urban areas is a real phenomenon globally, particularly in developing countries. This study aims to trace the origin of polycyclic aromatic hydrocarbons (PAHs) in the Abidjan district's rainwater and to evaluate the health risk to the population. Ten water samples were collected at two sites, during the dry and rainy seasons over a 2-year period. The use of molecular indices and profiles as well as Spearman's correlation matrix revealed that the pyrolytic sources, such as wood combustion as well as road traffic, remain the main sources of these pollutants in the water. The risk assessment revealed a higher risk of skin cancer in children.

Hydrochemical and groundwater quality of High Bandama watershed were investigated through thirty-five (35) samples composed of boreholes, hand pump wells and traditional wells. The analysis of physico-chemical parameters shows that groundwater is acidic with pH ranges from 3.2 to 6.9 and mean of 5.4. Electrical conductivity (EC) values were generally low and minimum and maximum were respectively 77 µS/cm and 553 µS/cm with an average of 250.3 µS/cm. Major cations (Ca 2+ , Mg 2+ , Na + and K +) were also generally low. Ca 2+ and Mg 2+ are being the most dominants cations with concentration values ranges from 4-56 mg/l and 0-55 mg/l respectively with mean value of 18.11 and 15.31 mg/l. 3 HCO − is the most dominant anion with minimum and maximum values ranging from 5 to 215 mg/l. According to WHO guidelines, groundwater quality is good for drinking. Piper diagram classified the hydrogeochemical facies into Ca-HCO 3 (48.57%), Ca-Mg-HCO 3 (31.43%), Ca-Mg-Cl (17.14%) and Na-Cl (2.86%) water type with one sample for Na-Cl. Compositional relation with plot of Ca + Mg versus HCO 3 + SO 4 and Chloro Alkaline Indice (CAI) confirms that the majority of groundwater samples (66.67%) exchange their ions Ca and Mg with Na and K from aquifer materials. Gibbs diagram showed that the rock-water interaction or weathering is the dominant process responsible of water chemistry.

<p>The Montagnes District is a metamorphic rocks area from Western Côte d’Ivoire covering an area of about 31,000 km<sup>2</sup>. Its capital is the city of Man. It is home to the largest industrial gold mine in Côte d'Ivoire, at Ity, with an annual production of 6 to 7 tons. Artisanal mining activities are also carried out in several places in the region. These activities can threaten groundwater, both in terms of quantity and quality. Therefore, a good understanding of the structure and functioning of aquifers in these mining areas is needed to prevent these impacts and to develop mining activities that are as environmentally friendly as possible.</p><p>This problem raises more generally the question of the validity of a hydrodynamic model explaining the origin of the permeability of hard rock aquifers in order to optimize groundwater resource management methods and better understand their vulnerability. To address this question, this work was able to rely on a statistical analysis of a database of 1654 boreholes.</p><p>Results shows that the structure of the aquifer is similar to that observed in several other hard rock areas in the world: it developed due to weathering processes, comprises the capacitive saprolite, 10–20 m thick on average, and an underlying transmissive fractured layer, overlying the unweathered impermeable hard rock. The fractured layer is about 80 m thick, the first 40 to 45 metres being its most productive zone, with a 11 m<sup>3</sup>/h median productivity.</p><p>The characterization of groundwater flow has led to the proposal of a new approach in the context of scarce piezometric data.</p><p>Finally, this research shows that the impacts of mining activities are local, limited mainly to the downstream part of the topographic watersheds where the mines are sited. There, groundwater quality and quantity may be affected, as well as the streams that drain these aquifers. In fact, surface water drains groundwater and therefore collects possible contaminants, downstream of the mines. A new approach to assessing the vulnerability of hard rock aquifers to contamination from mining has therefore been proposed.</p>