Flinders University research highlights new groundwater extraction methods to secure fresh water for Pacific atoll islands.
Hydrology experts at Flinders University are calling for urgent investigations into bore-field operations that access fresh groundwater on Pacific islands, particularly in Kiribati, where rising sea levels are placing local water supplies at risk.
“These atoll islands have the most threatened fresh groundwater on earth, and are relied upon by some of the most remote communities,” said Flinders University’s Professor Adrian Werner.
Research conducted by Flinders University suggests that a specialised form of fresh groundwater extraction, using horizontal wells, could help mitigate the risk of aquifer reserves being overused and provide drinking water with lower salinity levels.
These horizontal wells, known as infiltration galleries or skimming wells, are critical for extracting fresh groundwater on atoll islands. The system typically consists of horizontal or slightly inclined slotted pipes surrounded by a gravel pack, which connects to an extraction well or sump. This method allows for the skimming of fresh groundwater from shallow depths while minimising the risk of saltwater intrusion into freshwater lenses, which generally range between three and 21 metres in thickness.
Currently, these infiltration galleries are used across several atoll islands, with Flinders researchers focusing on nine small Pacific islands, including Kiritimati Atoll and Bonriki Island in Kiribati, Lifuka Island in Tonga, and the Cocos Islands.
While infiltration galleries provide vital freshwater supplies, there is limited information on their optimal layout, pipe characteristics, and pumping rates. Data on their performance, particularly in terms of pumping efficiency and salinity levels, is also scarce.
A research team from the National Centre for Groundwater Research and Training (NCGRT) at Flinders University, led by Professor Werner and Dr Amir Jazayeri, was commissioned by the Pacific Community (SPC) under the management of Mr Peter Sinclair to address these knowledge gaps. Their research evaluated the effectiveness of infiltration galleries across Pacific islands and included modelling to assess the potential impact of rising sea levels on these systems.
The study involved extensive data collection on the hydraulic properties of atoll island aquifers and an analysis of infiltration gallery designs across the region. Valuable insights were also gained through the Pacific Groundwater Gallery Knowledge Exchange (PGGKE) workshop, held on Kiritimati Atoll (Kiribati) in November 2023, where researchers engaged with infiltration gallery operators.
To further understand infiltration gallery performance, the research team incorporated computer modelling simulations and physical laboratory experiments conducted at Flinders University’s Sand Tank Laboratory. The findings have been published as a United Nations Development Programme (UNDP) scientific technical report, offering critical guidance for sustainable groundwater management in the Pacific.
“While many studies have examined horizontal wells in other contexts, the specific conditions of small islands, especially atolls, place unique demands on infiltration galleries,” said Professor Werner.
Dr Jazayeri highlighted the importance of ongoing research to protect freshwater resources and support remote Pacific communities. “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,” he said.
The research article, titled Construction and performance of infiltration galleries (skimming wells): A review of applications to Pacific atoll islands (2025) by Amir Jazayeri and Adrian Werner, has been published in the Journal of Hydrology (DOI:10.1016/j.jhydrol.2024.132581).
Professor Werner is confident that the research findings could have broader applications beyond the Pacific. “The insights gained from applying infiltration galleries to Pacific atolls offer 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,” he said. “This all contributes to global groundwater management strategies.”
He further emphasized the need for additional research into optimal infiltration gallery designs and their potential use in continental aquifers.
The study was funded by the Pacific Community (SPC) under the Managing Coastal Aquifers in Selected Pacific SIDS project (Contract No. 23–5419).
Source: Flinders University
