Analysis of the impacts of climate change on hydrological standards in West Africa: Case of Abidjan District (South of Ivory Coast)
Knowledge of quantiles of extreme precipitation as hydrological standards is required for the design of hydraulic projects and many other engineering applications. In the context of climate change in West Africa, the estimation of precipitation associated with extreme events is an issue to be adressed. This raises one main question: "On what basis can new quantiles be developed for the management of hydraulic work construction projects?" The objective of this study is the analysis of the impacts of climate change on the hydrological standards relating to the quantiles of maximum daily rainfall in the Abidjan District (southern Ivory Coast). The methodological approach used was to collect daily precipitation data covering the period 1961-2014. Basic statistical tests were performed. The choice of the statistical model was based on Gumbel's law. The parameters of the model were estimated and the quantiles calculated for several reference periods (1961-1990, 1971-2000, 1981-2010, 1961-2014) and return periods (2, 5, 10, 20, 50 and 100 years). A comparison of the quantiles determined was performed from the absolute relative deviation matrices. The main results showed that the different series defined are made up of independent, stationary, and homogeneous values. The quantiles calculated vary for a given return period as a function of the reference periods chosen for their determination. This reflects a non-stationarity of the quantiles due to climate instability. For improved safety of hydraulic works, the recommendation of this work is to use quantiles of the historical period (1961-1990) for return periods of less than 50 years. For return periods over 50 years, it is possible to use quantiles of two reference periods (1961-1990, 1981-2010). For the gradex value of the empirical methods of ORSTOM (Office de la recherche scientifique et technique outre-mer) and Inter-African Committee for Hydraulic Studies (CIEH), it is recommended to consider 0.44 for sizing hydraulic works in the Abidjan District.