Climate Change Impacts on Hydrodynamic Functioning of Oueme Delta (Benin)

Abstract

This work focused on quantification of the effects of climate change on the hydrodynamic functioning of the Ouémé Delta through the following steps. First of all, an analysis of the current state of extreme climate risks was conducted. Then, a future projection of the Ouémé River discharge at Bonou outlet was made in order to quantify the impact of anthropogenic activities and climate change by 2050. In addition, a mean ensemble model approach based on HEC-HMS, HBV and HyMoLAP was applied to better simulate Ouémé River peak flows at Bonou. Indeed, the hydrological simulation is done to generate the current missing flow data from 2011 to 2019. Finally, these flows were used to simulate water level and flows in the Ouémé Delta on the basis of the hydrodynamic model set up. Results showed increasing trend in extreme events. Similarly, the temperature is increasing as result of the current global warming. In addition, flows tend to decrease significantly with representative concentrations RCP4.5 while non-significant growth is observed with representative concentrations RCP8.5. HEC-HMS was the best among the three hydrological models to simulate both the Ouémé River daily and peak flow at Bonou. Thus, the outputs of this model over the period 2011- 2019 are then used for the hydrodynamic modeling. The hydrodynamic model set up allowed the correct simulation of the water level and flows in the Ouémé Delta. Thus, an inter-correlation between the water levels at Bonou, Adjohoun, Hêtin-Sota and So-Ava was established in order to reconstruct the water level and flows at Bonou in 2016. A good match between reconstructed flows and those simulated in HEC-HMS is observed. Thus, from the rain and temperature data over Ouémé catchment at Bonou Outlet, we can simulate water level and flow at any point in the Ouémé delta. Moreover, the combined effects of the governmental project of dams constructing and climate change will probably enhance existing ecosystem services issues in Ouémé Delta as Ouémé River flows in Bonou are expected to decrease by 2050. Therefore, ecological impacts studies have to be done for Ouémé Delta ecosystem sustainable preservation for the stakeholders’ wellbeing.