The water network
Currently, Rarotonga has a gravity-fed water distribution system that generally operates at high pressures and is the most comprehensive water supply infrastructure in the Cook Islands.
Streams and freshwater sources are collected from 12 intakes around the island that feed into storage tanks or directly into the distribution system. The distribution is an extensive pipe network, consisting of one ring main circumnavigating the entire island, and a series of cross mains and submains connecting water users. The reticulated network supplies residential homes, commercial and industrial sectors and major public institutions on Rarotonga.
The intakes are located inland, away from developed residential, commercial and industrial activities.
The existing reticulated water supply system is currently under stress due to unreliable rainfall patterns and excessive use. The current storage is not sufficient to maintain water supplies during drought periods and during these times water pressure can drop significantly and some intake points can dry up entirely.
Water losses due to the aging infrastructure are high. The Water Works division within the Ministry of Infrastructure Cook Islands (ICI) has reported water losses ranging from 30‐70% but recent upgrades to the ringmain have reduced the figure by around 20%.
The remote location of the intakes makes it difficult to carry out regular cleaning processes. Wild animals such as cows, goats, pigs etc are scattered throughout the catchment areas, and have easy access to the intake areas and contamination from faecal wastes is an on-going problem.
Like most Pacific island countries, Rarotonga has no chemical water treatment. Coarse gravel filters remove most solids and organic matter such as soil, leaves etc from the water but does not have the capacity to filter out bacteria.
Rarotonga is prone to floods during periods of heavy rainfall, during which shallow streams become inundated with sediment, rock and debris affecting the water supply. Flooding causes high turbidity, and the short passage time in the storage tanks fails to remove sediments, causing water users to complain of muddy water coming out of their taps.
There are only a few water storage tanks currently in operation managed by the Water Division, the Takuvaine tanks with a combined volume of 2.4 million litre capacity has only a 2-3 day storage for the Avarua town area, while the Tereora and Tepuka tanks are often prone to water shortage during low rainfall periods resulting in school closure and residents having to pay for water cartage.
Replacement and upgrading of the entire water network is currently in progress under the Te Mato Vai Project with the People's Republic of China and New Zealand. This project will rectify many of the problems outlined above.