Improving Water Security for Aitutaki

18 April 2018

Improving Aitutaki’s security of water supply is high on the priority list with numerous projects in the pipeline. Recently a team from Pacific Community (SPC) in Fiji visited the island to undertake electrical resistivity testing with the aim to identify potential locations for future development of water resources.  This initiative is a collaboration between the regional Water Security Project funded by NZAid and the Cook Islands Government.  The resistivity testing team was contracted under the Water Security Project, which is housed within the Office of the Prime Minister while the engineering aspects are handled by Infrastructure Cook Islands.

Aitutaki primarily relies on rainwater for its potable water supply (drinking and cooking only). Households collect rainwater from their own roofs and most have been supplied with 6,000 L polyethylene water tanks for storage. There are also approximately 16 community water tanks on the islands, in various states of repair, some of which have been repaired with help from donor agencies.

Non-potable (bathroom, cleaning, toilet, laundry, agriculture etc.) water supply is sourced from seven groundwater infiltration water galleries (three at Vaipeka; one at Vaipae, Tautu, Vaimaru and Vaitekea), with the Vaipeka galleries providing the bulk of the supply. Pumps supply water from the galleries to elevated reservoirs around the island from which the water is distributed to homes via a piped reticulation network. All galleries are operated by the Island Government and the water is brackish/saline.

“In most cases, since the onset of drought in November 2013 the recharge rates of groundwater has slowed down forcing the operating hours of the pumps at the galleries to be reduced. Recharge of the groundwater is very important to allow the water resource to recover” says Vicky Clarke of OPM.  Careful management of the groundwater harvesting must be done to ensure we don’t over utilize the resource and avoid pumping saline water into the reticulation system.

With the reliability on rainwater and gallery supplies (which are directly related to rainfall) for the island’s water supply, the island is prone to water shortages. The increase in variability in rainfall in recent times due to climate change means all the more important need to efficiently manage water supply on the island. Infrastructure Cook Islands and the Aitutaki Island Government are working together to develop new galleries and management plans to address the issue.

“The resistivity testing team from Fiji were on Aitutaki from the 3rd – 17th March and also held consultation meetings on Rarotonga with relevant stakeholders at either end of the trip. Staff from ICI and Aitutaki Water Works assisted with the work in order to build the capacity of our local staff.  The main objective of the investigation was to assess the potential for additional groundwater development using geophysics and to determine optimal locations and targets for drilling or gallery development” says Tenga Mana of ICI.

Other objectives of the investigation included undertaking groundwater sampling from existing wells/bore, monitoring of existing groundwater monitoring bores, calibration of the automatic rain gauges and investigation into spatial and temporal groundwater discharge mechanisms.  Electrical resistivity testing uses specialized equipment which sends an electrical current through the ground and measures how the ground material in the ground opposes the electric current. The data collected can then provide us with an approximation of the geology and hydrogeology of the area tested.  SPC and ICI have been working collaboratively with the Mei Te Vai Ki Te Vai team who will be undertaking further investigation work on Aitutaki in the coming months for wastewater project purposes.

Where to from here? “SPC are currently undertaking further work on the data collected and will deliver the results and recommendations to us in approximately 6 weeks’ time.  From here the next phase of the process will begin, which will be to undertake drilling to confirm groundwater targets and make an assessment of the yields available. Phase three of the work will then involve community consultation, water safety and security planning and design of new systems” adds Clarke.