POTENTIAL LOSSES OF FRESHWATER RESOURCES IN COASTAL AQUIFERS CAUSED BY CLIMATE CHANGE

Coastal regions, which include some of the most densely populated areas in the world, face various hydrological problems including saltwater intrusion in the aquifers. Saltwater intrusion, which is caused by several processes including sea-level rise, leads to groundwater quality degradation and results in loss of freshwater resources. Much of the debate on climate change and its associated impacts in coastal regions focus on the effect of sea-level rise on surface water environments. Sea-level rise resulting from climate change could enhance saltwater intrusion and lead to a decrease in freshwater supply from aquifers. Few studies, however, have been conducted to investigate the effects of climate change on freshwater resources in coastal aquifers. Many coastal aquifers involve heterogeneous permeability fields because they consist of complex deposits from transgression-regression cycles. The objective of this study is to investigate how sea-level rise caused by climate change affects saltwater intrusion and the freshwater supply in coastal aquifers. In particular, we focus on investigating the effects of heterogeneous permeability fields on the formation of the saltwater-freshwater interface and overall saltwater intrusion process. We conducted a series of numerical simulations to achieve this objective. Our preliminary results show that a large width of transition zone, in which saltwater mixes with freshwater to a great extent, along the saltwater-freshwater interface is formed because heterogeneous permeability fields in the aquifer facilitate the convective mixing process. A large width of transition zone indicates that a larger amount of freshwater will be degraded. The width of the transition zone greatly increases as the interface advances due to sea-level rise, and as the degree of heterogeneity increases. The results indicate that sea-level rise caused by climate change could decrease the freshwater supply to a greater extent than generally thought.