ScienceWise - Mar/Apr 2009

Rising tide

Article Illustration
Professor Ian White

Developing policies to help protect Kiribati’s water supply

As part of growing concerns over the effects of climate change on developing nations, The World Bank recently implemented an Adaptation Program for the multi-island Pacific nation of Kiribati, which has been supported by both AusAID and NZAID. As part of this program, Professor Ian White of the Fenner School of Environment and Society has been leading a team of scientists in helping Kiribati develop strategies to lessen the impact of climate change.

Professor White’s long experience of working in the region has led him to believe that “Understanding the local people and their lifestyle is vital to achieving success in any scheme like this. You have to build relationships and take the time to understand local culture. So rather than looking at this from a purely science perspective, we began by speaking to the locals and trying to build up a picture of what their concerns actually were.” One might imagine that in a nation of islands and lagoons, many of which don’t rise more than 6 metres above mean sea level, increasing sea levels would be the greatest worry to them. However, asked to rank priorities 7 out of the top 10 adaptation strategies concerned the far more immediate problem of fresh water supply.

The northern islands of Kiribati receive an average annual rainfall of between 2000 to 6000mm so outwardly it seems there should be no shortage of water. But the local soil is sandy and highly permeable, so in spite of the high rainfall, there is little run-off water. Instead, the rain permeates down into the ground, through the upper layers of corral sands and into the underlying karst limestone. The low terrain surrounded by ocean and the porosity of the system to tidal saltwater movement create a situation in which the underground fresh water tends to become saline. There is a layer of fresh ground water about 5 to 20 metres thick below which is 15 metres of intermixed water, then salt water.
Almost all the water for human consumption is extracted from this groundwater reservoir using wells or specially designed pumping systems. If a conventional vertical bore is pumped the suction tends to cause intermixing of the salt and fresh water, contaminating both the well and reservoir. So up to 300m long horizontal skimming wells are used instead. However the number and placement of such wells is critically important if the reservoir is not to become intermixed, so effective Government regulation and planning is vital.

Ironically, if sea levels do rise due to polar melting the initial effects will be positive for Kiribati. A small rise such as 0.5 m would tend to raise the fresh groundwater level into the coral sands and out of the karst limestone. This would reduce the tidal mixing process and in effect, increase the volume of fresh water available. However a rise of more than 0.5m would spell disaster for both the water reserves and the availability of land on these low flat islands.

But it’s not just geographical factors that influence the availability of water. Like many parts of the world including Australia, Kiribati is experiencing large scale migration of population from the outlying rural regions to the major centres of population where there are roads, schools, electricity and hospitals. In the small pacific island nation, this migratory population growth is exacerbating the water resource issue. Population densities in the capital Betio (pronounced Basio) are 12,000 people per square kilometre, something similar to central London! And more people mean more demand for water and more sewage to remove.

One of Professor White’s major concerns is the oceanography of the region. “Kiribati is even more susceptible to the whims of the Pacific El Niño Cycle than Australia, so we sometimes see a shift from the normal high rainfall to a situation of extreme drought.” Storms also pose a significant threat because even though most of the islands of Kiribati are outside the Pacific typhoon belt, there remains the possibility of a storm surge dumping vast quantities of sea water over the low terrain. “We know from experience on similar islands that when surge waves do pass right over the island, the ground water becomes highly saline and it can take the system up to 19 months to recover.” For all these reasons, Kiribati needs a national water policy and implementation plan to diversify the water harvesting methods and protect the future supply.

Professor White’s team have been able to help the government develop just such a comprehensive plan to secure Kiribati’s water resources over the coming decade. “But this has had to be a plan that works harmoniously with the local people and their traditions.” Professor White explains. “In Pacific communities things don’t happen overnight. In terms of communication, the people of Kiribati don’t naturally use the written word, preferring verbal communication or dance. It’s important to know these things in preparing effective policies and especially in developing appropriate plans of action.”

Although most of the residents of Kiribati have few of the material possessions that Westerners would associate with wealth, they don’t consider themselves poor. They place great value in family and in ownership of land, which provides produce such as coconuts and is also tied to local fishing rights. If the residents can be cushioned from impacts of climate change, in many ways the human experience of living in Kiribati is very positive.

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