Impact of major nearshore land reclamation project on offshore groundwater system

Abstract

Offshore groundwater (OG) systems are widely distributed in the coastal areas, where nearshore land reclamation projects are constructed for seaports, airports, and urban other infrastructures. However, there is almost no study on the interaction between these projects and the OG system. This paper presents the first such an effort using the Hong Kong International Airport near Lantau Island, as a case study by developing a three-dimensional density-dependent flow and transport model to investigate the interaction between the reclaimed airport and the OG system. Results show that the offshore relatively fresh groundwater may flow from the nearby Lantau Island through the submarine confined aquifer. The higher pore water pressure in the basal aquifer beneath the airport is generated by the regional groundwater system of the nearby Lantau Island. Besides, the reclaimed airport also serves as extra aquifer space for the storage of fresh groundwater resources. The expansion of the 3rd runway will further increase the water table and move the center of the water mound toward the 3rd runway area. The groundwater system in the airport will reach a new steady state 50 years after the expansion, and the volume of the fresh groundwater lens is calculated to be ~5.2 × 107 m3 with a maximum water table of 1.4 m above mean sea level. The findings of this study have implications on the large-scale nearshore land reclamation which may be affected by the OG system in other coastal areas.