EPOW - Ecology Picture of the Week

Trench well, North Andros Island, The Bahamas

Explanation:   This week we find ourselves in the remote north central area of Andros Island of The Bahamas in the Caribbean.  What is this long trench?  It is the Bahamian form of a water well.

The Bahamas is an island nation -- actually, an archipelago nation -- consisting of over 700 islands, 30 of which are inhabited.  Andros Island is the largest inhabited island and provides a source of drinking water for other islands.  

Hydrology of the islands is rather unique.  The islands consist of porous, low-lying limestone and marine sediments, through which fresh rainwater percolates and filters to form potable "sweetwater."  This long trench was dug to use gravity and percolation to collect the sweetwater which is pumped into holding reservoirs.  The water is then pumped into large tanker ships that ferry the water to the other islands which have no such freshwater.  One source says that nearly 7 million gallons of water are shipped daily from North Andros to Nassau.

This unique island hydrology also provides for the woodlands and vegetation of the island, including stands of Caribbean pine and understory plants including palmettos and shrubs.  

 
Drinkable "sweetwater" fills a shallow pool on North Andros 
Island of The Bahamas.  What looks like algae in the water 
is the limestone substrate that serves as a filter and catchment.