The ancient Sri Lankan 'tank cascades' tackling drought

Ajay0 · Oct 8, 2023

A 2,000-year-old Sri Lankan hydraulic system uses natural features to help harvest and store rainwater. In a rapidly warming world, it is providing a lifeline for rural communities.

The ancient Sri Lankan 'tank cascades' tackling drought

By releasing water into irrigation canals below, the tank supports the rice crop during the dry months before the rains arrive. For nearly two millennia, lake-like water bodies such as this have helped generations of farmers cultivate their fields. An old Sinhala phrase, "wewai dagabai gamai pansalai", even reflects the technology's centrality to village life; meaning "tank, pagoda, village and temple".

But the village's tank does not work alone. It is part of an ancient hydraulic network called an ellangawa, or "tank cascade system". As such, the artificial lake at Maeliya links up with smaller, man-made reservoirs upstream in the watershed. Together with their carefully managed natural surroundings, these interconnecting storage structures allow rainwater to be harvested, shared and re-used across the local area.

Constructed from the 4th Century BC up to the 1200s, these cascade systems have long helped Sri Lankan communities cope with prolonged periods of dry weather. "As most of the country is made up of crystalline hard rock with poor permeability, it induces runoff, " says Christina Shanthi De Silva, senior professor in agricultural and plantation engineering at The Open University of Sri Lanka. "Our forefathers built tank cascades to capture this surface runoff," she explains, preventing it from being washed away into rivers and, ultimately, the sea.
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wilsjane · Oct 9, 2023

Here in the UK, a large amount of water has been pumped from deep wells, since Victorian times.
This is the pumping station and water pressurisation tower at Kempton Park.

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The ancient Sri Lankan 'tank cascades' tackling drought

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