Why are there no rivers on most of Tonga's islands?

Most of the islands in Tonga lack rivers primarily due to their geological composition. Many of these islands are formed from coral and limestone, which are porous materials that allow water to permeate the ground rather than forming surface streams.12

Because the land is composed of calcium carbonate, rainwater reacts with carbon dioxide in vegetation to become acidic, which dissolves the rock and creates subterranean drainage systems rather than surface riverbeds. Consequently, fresh water on these islands is typically collected in rain catchments or drawn from wells. While there are no rivers on most of the islands, some, such as ‘Eua and Niuatoputapu, do possess creeks.12