Water

St. Helena was founded on a territory that is part of the vast Banat Karst area. The various types of limestone were formed in warm, shallow, Mesozoic seas, which were full of life, and were lifted up from the seas onto land in the Tertiary. But during this uplift (the Alpine-Himalayan orogeny, which is still going on today), the limestone blocks were also broken by enormous geological forces. As rainwater flowed through the cracks, it slowly dissolved the limestone and started numerous karst phenomena that have a profound effect on water management in St. Helena’s landscape. The karst phenomena may include shafts, caves and sinkholes. Sinkholes are places where water quickly leaves the surface and flows into the limestone block. The karst landscape is therefore relatively dry. The bottoms of sinkholes, on the other hand, are unique habitats. They have high levels of water retention, but also a deeper layer of relatively fertile soils that have been washed in from the surrounding areas by surface water. That is why you might see little fields, orchards or gardens in the sinkholes.

The locals had to find ways to cope with the limited water supply. Originally, drinking water was transported from springs and kept in tanks, and for other uses, there was rainwater.