Hydrodynamic modeling of Sharjah lagoons under climate changes, United Arab Emirates (UAE)

The lagoons of Al Khalid, Al Khan and Al Mamzar are among the most important natural assets in the Emirate of Sharjah, as they play an essential role in the coastal socio-economic environment of the area. However, the hydrodynamics of these lagoons in the context of climate change has never been studied. This study presents the results of a hydrodynamic model applied to these lagoons to determine water circulation and flushing time variability, both at present, and in a future with a projected 1m sea level rise (SLR) over the next 100 years. The results show that a 1m SLR would increase the tidal range by 35% and raise the velocity of currents inside the lagoon from an average speed of 0.31 m/s (present) to 0.43 m/s (future), with maximum currents of 1.4 m/s occurring near the tidal inlet during the flood tide and 0.8 m/s during ebb tide. This increase in tidal velocity would also increase the rate of water circulation in the lagoons, significantly reducing the local flushing time. The present conditions revealed that inner areas of the lagoon experience increased local flushing times compared to the outer regions of the lagoon, which may impact water quality status in the inner sectors. Overall, in the model, the local flushing time was reduced from 27 days (present) to 14 days (future), reflecting a 50% reduction. This would suggest that a 1m SLR would result in a more efficient dispersal of materials out of the lagoons.