Terrestrial or oceanic forcing? Water level variations in coastal lagoons constrained by river inflow and ocean tides

The study concerns the water level (WL) evolution in lagoons under influence of tides and river fluxes. We derive new approximate analytical solutions Stigebrandt (1980) equations apply them to Nokoué Lagoon (Benin), a large tropical coastal lagoon fed by substantial input. show accurately predict mean WL tide amplitude. In particular nonlinear combination spring-neap tidal cycle inflow gives rise strong fortnightly variation WL. are used explain this phenomenon. also calculate phase shift between ocean asymmetry ebb flood duration lagoon. first increases with flux but reduces above critical before becoming symmetric again at peaks. Finally, inverted estimate net fluxes entering Lagoon, where no observations available for rivers which we have high frequency 2 years. model is calibrated using few channel connecting ocean. Realistic estimated. subsequently variations simplified forced recalculated forcing from an model. solution represents over year time period study. conclude that simple able represent complex interaction fluxes, its on low lagoons.