Hydrogeochemical characterization and suitability study of dug well water for domestic purpose were carried out in a semi-arid rural village in Burkina Faso. Thirty water samples were collected from 15 wells in dry and wet seasons, 2017. Electrical conductivity (EC) and total dissolved solids as well as major ions of all samples were within the World Health Organization (WHO) permissible limits for drinking water. In contrast, nine wells had pH beyond the WHO limit during the dry season and one well had very high NO3- concentration in the wet season. Most wells were seriously polluted with total Cr (CrT) in both seasons (11 and 14 wells in dry and wet seasons, respectively). Although Pb was not detected in the wells during the dry season, six wells showed Pb concentrations exceeding the WHO guideline limit for drinking water in the wet season. Graphic interpretation, including the Piper diagram, major ion ratios and Na/Cl versus EC, were used to characterize the hydrochemistry and water – rock interaction within the wells. The dominant hydrochemical facies of the wells was Ca-HCO3 during the dry season, reflecting the influence of silicate weathering. Following loadings of agricultural and domestic effluent, the hydrochemical facies shifted to more mixed type during the wet season. All samples had negative chloro-alkaline indices, suggesting retention of Ca2+ and Mg2+ by the aquifer materials and release of Na+ and K+ into the groundwater. In addition to silicate weathering, the hydrochemistry and water quality of the majority of the wells were partially controlled by the evaporation process and longer water–rock interaction in the dry season. In contrast, recharge and dilution effects appeared to alter the natural hydrochemistry of the wells in the wet season. Geochemical characterization has clearly shown that seasonal changes do affect the dug well water quality. The study also demonstrated that, in terms of CrT and Pb, water from the majority of the wells was not suitable for drinking. A special attention should be therefore paid to groundwater quality protection in the

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Watershed degradation is a key issue for environmental change in the Sahel region and causes an unprecedented threat to the lowlands watershed and the livelihood of local people. This study analyzes the spatial dynamics and degradation risks of Nakanbé-Dem sub-watershed lowlands'potential. The study combines lowlands plants species assessment and digital processing. Lowlands spatiotemporal dynamics were assayed from landsat images of 1986, 1996, 2006 and 2016. Vegetation data and soil physical and chemical parameters allowed to characterize lowlands degradation states. Lowlands degradation risk assessment is based on flora analysis and remote sensing indices (Normalized Difference Vegetation Index, Normalized Difference Water Index, slope values and water accumulation zones). Spatio-temporal dynamics analysis between 1986 and 2016 showed a continuous degradation of Nakanbé-Dem lowlands potential. The coverage of farming land increased from 31 to 51% compared to the total lowland potential of 43320 ha. The riparian formations have decreased by 4.11% in the same period. As concerns the lowland beds, their coverage rate has continuously decreased from 24% in 1986 to 7.79% in 2016. The coverage rate of water bodies has not kept a linear evolution. It went from 2.27 to 2.62%, a slight increase of 0.35%. Soil and flora samples were taken from the three lowland geomorphological subunits: glacis, hillside and the central

Predominant volcano-plutonic (mafic-felsic) activity is expressed in the eastern Banfora Belt (BB). Geochemical signature shows different geodynamic settings: i) mafic rocks are tholeiitic, sub-alkaline and show high-Mg tendency, whereas pyroxenolite (MgO ∼ 15.4 wt%) has komatiite affinity; ii) felsic volcanic rocks are sub-alkaline; iii) granitoids surrounding the BB are alkaline to calc-alkaline, high K, peraluminous to metaluminous. Geochemistry of mafic volcanic rocks shows an unusual an evolution from Middle Oceanic Ridge Basalt (MORB) to Arc-related. The Western Granite (WG) and Eastern Granites (EGs) emplaced by fractional crystallization and partial melting respectively, but sourced from igneous protolith (I-type magma) in volcanic arc setting (VAG). The Sodingue granite emplaced by fractional crystallization from A-type magma in “within plate setting”. Two-micas S-type granites located at the central portion of the belt and relate to syn-collisional fractional crystallization. The paper highlights the complexity of magma process throughout a diversity of sources, geochemical pattern and tectonic setting. An emphasis on the komatiite affinity of mafic magma is a challenge for related commodities, such as copper and gold resources.