West African basins play a vital role in the socio-economic development of the region. They are mostly trans-boundary and sources of different land use practices. This work attempts to assess the spatio-temporal land use and land cover changes over three South Western African basins (Volta, Mono and Sassandra basins) and their influence on discharge. The land use and land cover maps of each basin were developed for 1988, 2002 and 2016. The results show that all the studied basins present an increase in water bodies, built-up, agricultural land and a decline in vegetative areas. These increases in water bodies and land use are as a result of an increase in small reservoirs, of dugouts and of dam constructions. However, the decline in some vegetative clusters could be attributed to the demographic and socio-economic growth as expressed by the expansion of agriculture and urbanization. The basic statistical analysis of precipitation and discharge data reveals that the mean annual discharge varies much more than the total annual precipitation at the three basins. For instance, in the entire Volta basin, the annual precipitation coefficient of variation (CV) is 10% while the annual discharge CV of Nawuni, Saboba and Bui are 43.6%, 36.51% and 47.43%, respectively. In Mono basin, the annual precipitation CV is 11.5% while the Nangbeto and Athieme annual discharge CV are 37.15% and 46.60%, respectively. The annual precipitation CV in Sassandra basin is 7.64% while the annual discharge CV of Soubre and Dakpadou are 29.41% and 37%, respectively. The discharge varies at least three times much more than the precipitation in the studied basins. The same conclusion was found for all months except the driest months (December and January). We showed that this great variation in discharge is mainly due to land use and land cover changes. Beside the hydrological modification of the land use and land cover changes, the climate of the region as well as the water quality and availability and the hydropower generation may be impacted by these changes in land surfaces conditions. Therefore, these impacts should be further assessed to implement appropriate climate services and measures for a sustainable land use and water management.

Climate and land use/cover changes are potential drivers of change in hydrology and water use. Incidences of these factors on Bandama hydrological basin and Kossou hydropower generation (1981–2016) in West Africa are assessed in this present work. Using Landsat products of United Stated Geological Survey, results show that water bodies areas and land use have increased by 1.89%/year and 11.56%/year respectively, whereas herbaceous savanna, savanna, forest and evergreen forest coverage have been reduced by 1.39%/year, 0.02%/year, 2.39%/year and 3.33%/year respectively from 1988 to 2016. Hydroclimatic analysis reveals that streamflow presents greater change in magnitude compared to rainfall though both increasing trends are not statistically significant at annual scale. Streamflow varies at least four (two) times greatly than the rainfall (monthly and seasonally) annually except during driest months probably due to land use/cover change. In contrast, Kossou hydropower generation is significantly decreasing (p-value 0.007) at both monthly and annual scales possibly due to water abstraction at upstream. Further works are required to elucidate the combined effects of land use/cover and climate changes on hydrological system as well as water abstraction on Kossou generation.

The streamflow is important for planning et decision-making of development activities  related to water resource. The hydrological mathematical models are frequently used to simulate the transformation of rainfall into streamflow as well as Artificial Neural Networks (ANNs. In order to contribute to the establishment of an adequate framework for water resource management in the Davo river basin, this study presents an intercomparison between streamflow estimations from conventional hydrological modelling and ANN analysis. The Davo River basin is located in the southwestern forest of Côte d'Ivoire. The hydrological models used are the HEC-HMS model (Hydrologic Engineering Center-Hydrologic Modeling System) and the GR4J model (Rural Engineering with four daily parameters), while the data-driven ANN model is developed in MATLAB. The three tools receive the same data and their parameters are calibrated using the same objective functions. The quality of the simulations is measured in the control phase using several statistical criteria. For the assesment of the impacts of climate change on hydrological regime of the Davo river basin, the AFRICA-CORDEX (Coordinated Downscaling Experiment for Africa) data under two RCP (representative concentration pathway) scenarios   RCP4.5 and RCP8.5 are integrated in the three tools of modelling. The approach developed in this study allows a considerable improvement of the outils performances developed in calibration and validation. In addition, the results of the current study provide valuable feedback for water resources’ planners in Côte d’Ivoire and the developing regions.Keywords: Climate change, Streamflow, Artificial Neural Networks, HEC-HMS, GR4J, Davo river basin, Côte d’Ivoire