Characterization of hydropluviometric variability in the lower valley of the Ouémé

Abstract

Over the past 30 years, West Africa has been hit by climate variability. This variability affects the activities of the poorest populations. This situation makes communities vulnerable to the effects of climate change. The aim of the present study is to characterize hydroclimatic variability in the lower Ouémé valley. To achieve this, rainfall and flow records from the Bonou station were collected over the period 1986-2016. These data, obtained from the national meteorological agency and the Direction Générale de l'Eau, were processed and filled in. Statistical protocols were used to determine the characteristic elements of hydro-climatic variability in the environment. The pettitt test was used to determine any breaks in rainfall and flow rates. Analysis of the results revealed an uneven distribution of rainfall. Three phases were identified in the evolution of rainfall. The first, 1987-1990, was marked by rainfall surpluses. The second is characterized by rainfall deficits between 1990 and 2006, and the last (2006-2016) by very unstable rainfall trends. Application of the Pettitt test to this time series revealed a break in stationarity at the 95% threshold, highlighting two sub-periods, 1987-2006 and 2007-2016. This drop in rainfall leads to a drop in surface runoff, with values ranging from 0.2% to 1% in the Ouémé valley.