Vulnerability of Groundwater Resources in Tongatapu 2011

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Tongatapu, Tonga : Water

Two thirds of the population of the Kingdom of Tonga, live on the small, South Pacific raised
limestone island of Tongatapu. Groundwater is the principle source of reticulated fresh water both in
the capital Nuku’alofa and in rural villages and is sourced from a relatively thin, fresh groundwater lens
overlying seawater. This paper describes a comprehensive, integrated assessment of the vulnerability
of fresh groundwater in Tongatapu. Water resources policy and legislation, and the organisation
structures for regulating and managing of water were examined. Threats to groundwater from
seawater intrusion, overpumping, agriculture, waste disposal, industry, quarrying, urban settlements,
population growth, droughts and climate change were analysed using existing data and field
measurements. The impact of pumping on freshwater salinity is clearly discernible within ENSO
signatures. Suggestions are made for improving the protection of water resources, mitigating saline
water impacts, enhancing freshwater supplies and for reforming regulation and management.