By Pacific island Times News Staff
Hydrology experts at Flinders University in Australia are seeking further study into the method of drawing fresh groundwater that make use of borefields. in several Pacific islands and atolls
“These atoll islands have the most threatened fresh groundwater on earth, and are relied upon by some of the most remote communities,” said Adrian Werner, a professor at Flinders University.
Werner co-authored a study on hydraulic properties of atoll island aquifers, analyzing the design of horizontal wells, also known as infiltration galleries or skimming wells.
The study focused on nine small Pacific islands, including Kiritimati Atoll and Bonriki Island in Kiribati, Lifuka Island in Tonga and the Cocos Islands.
Extracting fresh groundwater in many Pacific islands, particularly atolls, often involves the installation of horizontal or inclined perforated pipes, connected to an extraction well/sump containing a pump.
The infiltration galleries skim fresh groundwater from shallow depths while minimizing the risk of saltwater intrusion beneath thin subterranean freshwater lenses, which typically range 3 to 21 meters in thickness.
Researchers said the design, construction and operation of these galleries need to be precise to avoid drawing seawater into the island’s water supply.
“Notably, we found a lack of investigations optimizing gallery design in terms of the aforementioned characteristics, leaving this as a critical area for future research effort,” states the study co-authored by Amir Jazayeri and published this month in the Journal of Hydrology.
“While many studies have examined horizontal wells in other contexts, the specific conditions of small islands, especially atolls, places unique demands on infiltration galleries,” Werner said.
The study found that that there is also limited data on the performance of these galleries – specifically pumping rates and salinity levels – on small atoll islands.
Jazayeri said the research team continues to focus on solutions to protect freshwater resources and serve the demands of isolated communities across the Pacific, using a wide range of research techniques.
“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 said.
Werner is confident the findings will have wider applications across many countries.
“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,” he said. “This all contributes to global groundwater management strategies.”
Werner and Jazayeri led the team from Flinders’ National Center for Groundwater Research and Training to conduct the research commissioned by the Pacific Community.
“Our review compiles information on infiltration gallery layout, pipe characteristics and pumping rates, as well as the performance of infiltration galleries (pumping rates and salinities), among other aspects,” the study said.
“For example, infiltration gallery assessments should account for freshwater lost as discharge to the sea and through mixing with saltwater – key components of the water budget often overlooked in atoll island water-balance analyses."
The authors said the insights gained from applying infiltration galleries to Pacific atolls offer opportunities for more widespread applications within continental aquifers, such as capturing submarine fresh groundwater discharge that is otherwise lost through mixing with seawater and mitigating seawater intrusion.
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