Dynamics in salinity diffusion influenced by anthropogenic pressures and climate change: a case study of the Aghien lagoon (Abidjan, Côte d’Ivoire)

By 2070, the Aghien Lagoon, which is influenced by both riverine and marine inputs, is expected to experience the cumulative effects of anthropogenic activities particularly the opening of the Comoe river estuary and climate change. However, the medium-term impact of these pressures on the lagoon’s salinity dynamics has never been assessed. This study aims to evaluate the influence of these factors on the salinity dynamics of the Aghien lagoon up to 2070. To this end, discharge and water level data were collected. Depth and salinity measurements of the tributaries and the lagoon were conducted before and after the opening of the estuary. The collected data were then used to validate a hydrodynamic and salinity diffusion model. Simulations indicated that a sea level rise under the SSP5-8.5 scenario would result in a salinity increase of approximately 0.3 PSU, representing a 200% rise. However, this increase appears to have no effect on the salinity of the northern part of the lagoon, where water abstraction activities would take place. Consequently, the Aghien Lagoon could potentially be used for drinking water production by 2070. Nevertheless, a more comprehensive understanding of vertical salinity variation within the lagoon necessitates three-dimensional modelling.