Department of Infrastructure and Regional Development

Christmas Island Groundwater Project

Dolly Beach.

Christmas Island is an external Australian territory located in the Indian Ocean about 2600 km north-west of Perth and 350 km southwest of Java. The Island is approximately 135 km2 in size and has a population of around 1200–1500 residents. Although the average yearly rainfall is approximately 2000 mm/year, the Island has experienced periodic droughts that have threatened water supplies.

Because of the highly porous rocks of the island, no permanent surface water bodies exist, and all fresh water is sourced from natural springs and caves.

Currently, the Island’s water supply is treated and stored in above-ground tanks, however, this only provides sufficient storage for a two-day supply if the underground water (groundwater) dries up or is contaminated.

The Department of Infrastructure and Regional Development commissioned Geoscience Australia to identify and assess new potential underground water resources across the Island.

The project will also identify potential seawater intrusion risks and how the groundwater system connects as a whole. The data and knowledge generated in the project is expected to provide valuable new insights into the geology of the island more generally.

Volcanic breccia.

Project Benefits This project will improve water security on the Island by:

• providing critical new data and knowledge of groundwater resources for the Island;

• informing sustainable land management practices;

• underpinning economic development and planning; and

• providing new data on the 3D geology of the Island.

View of Flying Fish Cove.

The ‘Blowholes’.

Results to dateStage 1 of the project saw Geoscience Australia complete an initial scoping study in February 2017.

The study confirmed Christmas Island’s geology and hydrogeology is complex and poorly understood. The Island’s groundwater system is likely to be highly compartmentalised, with the potential for groundwater supplies to be identified in several locations across the Island.

North EastPoint

North WestPoint

EgeriaPoint

SmithsonBight

INDIANOCEAN

FlyingFishCove

SouthPoint

DollyBeach

GretaBeach

ChristmasIsland

Airport

MurrayHill

West WhiteBeach

LilyBeach

MiddlePoint

105°40'E105°35'E

10°25'S

10°30'S

10°35'S

0 5 km

AUSTRALIA

ChristmasIsland

!

PP-372-1

Elevation (m)

-5

359

o

Topographic map of Christmas Island.

GA PP-376 | eCat 104423

Next StepsGeoscience Australia has recommended a second phase of investigations, commencing with ground geophysics to assess the potential for 3-dimensional mapping of the Island using below ground imaging technologies (airborne electromagnetics and magnetics).

Stage 2 of the project will use these technologies, complemented by drilling and water sampling, to identify and assess new potential underground water resources across the Island. Stage 2 is expected to commence in mid-2017.

Volcanic rock pedestal at Dolly Beach.

For Further Information:

Geoscience Australiaclientservices@ga.gov.au

Department of Infrastructure and Regional DevelopmentIndianOceanTerritories@infrastructure.gov.au

© Commonwealth of Australia (Geoscience Australia) 2017. This material is released under the Creative Commons Attribution 4.0 International Licence.

Geoscience AustraliaGPO Box 378Canberra ACT 2601www.ga.gov.au