Tarawa atoll is within the Gilbert group of islands in Western Kiribati
South Tarawa
Main urban area in Kiribati, with the 2010 census recording 50,182 people of the more than 103,058 total population
Bonriki Water Reserve
Primary raw water supply for the Public Utilities Board reticulated water system used by at least 67% of the population
Bonriki Freshwater Lens
The groundwater system under the atoll island is in a delicate balance between rainfall recharge and sea water instrusions
Atoll Hydrology
Groundwater water levels are highly variable due to their close relationship with water levels in the lagoon and ocean


Atolls islands are low-lying reef carbonate islands. They usually consist of a series of narrow islands or motus surrounding a relatively shallow seawater lagoon. There are 261 atolls among the south-west Pacific Ocean. The largest number of atolls (77) are found in French Polynesia (Tuamotu Archipelagos)

Analytical Groundwater Model

An analytical model solves highly simplified representations of aquifers (e.g. properties of the aquifer are considered to be constant in space and time, aquifer geometry is uniform) to enable a rapid solution to a given problem.

Numerical Groundwater Model

A numerical model divides space and/or time into discrete pieces, enabling more complex and potentially more realistic (relative to analytical models) representations of a groundwater system to be developed. Two dimensional cross-sectional numerical models consider only a vertical slice of the study area. Three dimensional numerical models consider areal and vertical extents of the study area.

Physical Groundwater Model

A common form of physical model is the sand-tank, which is used to visualise physical processes, albeit under highly simplified and smaller-scale conditions than encountered in the field, that are otherwise difficult to observe.