Land reclamation and its consequences: A 40-year analysis of water residence time in Doha Bay, Qatar

Hanert, Emmanuel [UCL] Lecart, Mathieu [UCL] Dobbelaere, Thomas [UCL] Alaerts, Lauranne [UCL] Randresihaja, Ny Riana [UCL] Mohammed, Aboobacker Valliyil [Qatar University] Vethamony, Ponnumony [Qatar University] et al.[show all]

In recent decades, the Arabian/Persian Gulf has seen a boom in land reclamation projects, that completely reshaped its coastline. These projects were designed to capture public attention and offer prime real estate as exemplified by The Palm and The World Islands in Dubai. In Qatar, the rapid urban expansion of the capital city, Doha, has encroached upon the sea, leading to a constriction of the entrance to Doha Bay. By reducing and deflecting the ocean circulation, land reclamation projects have reduced the effective dispersion of wastewater introduced into the Bay and hence degraded the water quality. Here, we assess fluctuations in water residence time, i.e. the time needed for a water parcel to leave the Bay, across three distinct eras (1980, 2000, and 2020) to gauge the impact of successive land reclamation developments. To do this, we couple the multi-scale coastal ocean model SLIM with a Lagrangian model for water residence time within Doha's coastal area. We consider three different topographies of Doha's shoreline to identify which artificial structures contributed the most to increase water residence time. Our findings reveal a modest rise in residence time, of about one day on average, between 1980 and 2000, followed by a substantial surge, of three to six days on average, between 2000 and 2020, which is mostly attributable to The Pearl mega artificial island development. Certain regions of the bay witnessed a tripling of water residence time. Given the ongoing population expansion along the coast, it is anticipated that the growth of artificial structures and coastal reclamation will persist, thereby exacerbating the accumulation of pollutants in the Bay. Our findings suggest that artificial offshore structures can exert far-reaching, non-local impacts on water quality, which need to be properly assessed during the planning stages of such developments.