The main objective of this study is to asssess the impacts of climate change and land cover change on the hydrology of the Davo river basin located in southwestern of Côte d'Ivoire. Two scenarios of climate change (A2 and B2) and two scenarios of land cover called scenario 1 (deforestation) and scenario 2 (reforestation) were established, and streamflows under these scenarios were simulated by the hydrological model CEQUEAU. Each scenario showed distinct variations in streamflows. Regarding the impacts of land cover change, scenario 1 and scenario 2 indicate increases of 10.6% and 1%, respectively. As for the impacts of climate change, climate models predict a very wide range of possible changes in streamflows. The multimodel approach indicates a decrease in streamflows of 0.5% and 2.75% respectively under the A2 and B2 scenarios by 2050. By 2080, streamflows would increase by 14.75% under the scenario A2 and 3.5% under scenario B2. In order to implement adaptation and mitigation strategies, Representative Concentration Pathways (RCP) scenarios should be used, regional climate models should be applied, and combined assessments of the impacts of climate change and land cover should be made.

This study objective is to evaluate Gumbel's law exclusive use relative error of the in favor of theoretical and practical laws in extreme rainfall quantile estimation. To do this, an extreme rainfall database from 1941 to 2000 from the Bianouan, Agnibilékro, Adiaké and Ayamé rainfall stations on the Bia River watershed was established. The results analyzes show that the Fréchet and normal Log 2 laws are respectively the ideal laws of the theoretical and practical approach. In addition, a Gumbel's law exclusive use underestimates extreme rainfall quantiles compared to two approaches. Thus, Gumbel's law use could be justified by an economic or operational issue insofar as it understates the structures while minimizing the cost.

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).