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SEA Currents Blog

SEA Currents: General


March 22, 2016

Cloudy with a Chance of Fresh Water

Jan Witting, Professor of Oceanography, Sea Education Association

SEA Semester

Cistern on the island of Rangiroa in French Polynesia.

How do you feel about rainy days? I have a hunch that most of you are like me, and far prefer prefer blue skies to drizzle and rain. Yet it is a pretty indulgent relationship with water, something we can afford thanks to municipal water supplies and secure access to it. Something that can quickly make this fact plain to us is a trip to an atoll island pretty much anywhere. I remember waking up to the sound hard rain hammering the tin roof of my friend Herve’s house on the island of Rangiroa in French Polynesia some years ago. Facing the prospect of a soggy day and no hope of any change in the clouds, I turned to Herve to express my disappointment only to find a broad grin on his face.  “The Paumotu are happy when it rains,” he explained, and pointed to the big cistern that was being fed by pipes from the gutters of the house.

On these islands, the collected rainwater serves as the main source of fresh water. A coral atoll is like a string of pearls, typically made of many small islands ("motu," in most Polynesian languages) isolated from each other by shallow channels through which seawater flows in and out of the central lagoon. These low-lying motu made of coral rock and sand are very permeable, and while in some places on the larger ones there can be a small lens of fresh groundwater, it is often brackish from salt water intrusion. So from ancient times people survived on rainwater and, during dry spells, shallow wells.

There are no better places to find the effects of the changing climate than the hundreds of atolls in the Pacific. With increasing temperatures come changes in winds and humidity, making some places drier, others wetter. In either case, the fine balance of evaporation and precipitation that waters the plants and the peoples of these islands is disrupted. In the ancient times, the Polynesians would readily move with seasonal patterns among the motu and other atolls on their remarkable seafaring vaka, or double hulled (or outrigger) canoes. That model is less suited to modern times and more persistent changes, and in many of these beautiful islands the supply of fresh water is the largest challenge for the survival of the island communities.

So amidst such uncertainty, for the islanders dark clouds have something far better than mere silver linings. They bring water and smiles.

Categories: General, • Topics: polynesia.  climate change • (0) Comments

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