Hydrology experts at Flinders University emphasize the need for innovative groundwater extraction methods to secure freshwater resources on Pacific islands facing the threat of rising sea levels.
Researchers from Flinders University are urging for an urgent review of bore-field operations to protect freshwater resources on Pacific islands such as Kiribati, where rising sea levels pose a critical threat to local water supplies.
“These atoll islands have the most threatened fresh groundwater on Earth and are relied upon by some of the most remote communities,” Adrian Werner, a professor of hydrogeology at Flinders University, said in a news release.
A team from the National Centre for Groundwater Research and Training (NCGRT) at Flinders University, led by Werner and Amir Jazayeri, a research associate, has identified a pressing need for specialized groundwater extraction techniques. This comes as traditional methods risk exacerbating the issue of saltwater intrusion, compromising already scarce freshwater supplies.
The researchers have focused on a specialized form of groundwater extraction, known as infiltration galleries or skimming wells, which can significantly reduce the risk of overusing aquifer reserves. These wells, essential for extracting fresh groundwater on atoll islands, typically consist of horizontally or slightly inclined slotted pipes surrounded by a gravel pack and connected to an extraction well.
These infiltration galleries can skim fresh groundwater from shallow depths while minimizing the intrusion of saltwater into already thin freshwater lenses.
The team’s extensive research has taken them to nine small Pacific islands, including Kiritimati Atoll and Bonriki Island in Kiribati, Lifuka Island in Tonga and the Cocos Islands. Despite the critical role these wells play, the optimal layout and pumping rate characteristics remain under-studied.
At a recent Pacific Groundwater Gallery Knowledge Exchange (PGGKE) workshop on Kiritimati Atoll, valuable insights were gathered from operators of these systems. Further, the research incorporated computer modelling and laboratory experiments at Flinders University’s Sand Tank Laboratory, culminating in a comprehensive scientific technical report published by the United Nations Development Programme (UNDP).
“While many studies have examined horizontal wells in other contexts, the specific conditions of small islands, especially atolls, place unique demands on infiltration galleries,” added Werner.
Looking ahead, the researchers intend to leverage this knowledge for broader applications, especially within continental aquifers.
“We believe that expanding the use of infiltration gallery systems in other coastal aquifers can significantly contribute to managing crucial coastal freshwater resources, both in Australia and globally,” Jazayeri added.
The conclusions from the study, published in the Journal of Hydrology, underscore the potential for infiltration galleries to capture submarine fresh groundwater discharge, which would otherwise mix with seawater and to help mitigate seawater intrusion. The researchers advocate for additional studies to refine these techniques and apply them more widely.
“The insights gained from applying infiltration galleries to Pacific atolls offers opportunities for more widespread applications within continental aquifers, especially to capture submarine fresh groundwater discharge that is otherwise lost through mixing with seawater and to mitigate seawater intrusion,” Werner added. “This all contributes to global groundwater management strategies.”
Source: Flinders University