From medium-resolution satellite images (Landsat TM, ETM+ and OLI), the spatial dynamics of land cover and land use are highlighted. The objective of this study is to quantify the evolution of land use in the watershed of the Lobo River upstream of Nibéhibé between 1986 and 2019 in order to analyze the impacts of human activities on the landscape. The study method was based, on the one hand, on the processing of satellite images, for the analysis of the dynamics of land use and, on the other hand, on the CA-Markov model, for the prediction of land use by 2050. It emerged from this study that the land use maps produced made it possible to highlight the spatio-temporal dynamics of land use on the basin. For the period from 1986 to 2019, there is a decrease in the area of forests in favor of built-bare ground and crops and fallows. A land use scenario for the years 2019 and 2050 was simulated with an accuracy of 87.11%. The regressive trend in forests seems to continue in the future with current land use practices.

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The expansion of agro-industrial exploitations and the increased use of pesticides is a major concern for the quality of groundwater resources in the Abidjan area. The objective of this study is to assess the global vulnerability to pollution of these resources. Therefore, two methods based on the DRASTIC model were used. These methods are DRASTICLU and DRASTICLU-P in which land use is considered as a parameter, extending to 8 the number of analyze parameters in order to make the results more robust. To assess the significance of different parameters, a sensitivity test has been calculated. Validation of the results was made from the calculation of map error (Er) on the resulting maps, to see which is best suited for this study. The results show that the global vulnerability to pollution remains generally high in the area. These areas of high and very high vulnerability are found on almost all of the study areas, but with a strong presence in center and north. Together, high and very high vulnerability cover almost 84% of the study area. These areas are highly dependent on the recharge, aquifer media, soil media and the vadose zone. The calculation of uncertainties gave relatively high values due to high overall standard deviations. Calculated map errors are 22% and 21.5% respectively for DRASTICLU-P and DRASTICLU. Although these values are substantially equal, show that the DRASTICLU-P method remains the most suitable.

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