Biological CleaningIrrigationNatural SwimmingRegional Water CycleWaste WaterWater ConservationWater Harvesting

Letters from Sri Lanka – Greywater Recycling at Kuttam Pokuna (the Twin Pools)

Novice Buddhist monks listen to their instructor
Photos Copyright © Craig Mackintosh

Last time I spoke about the world’s largest earthworks project – an incredible and unrivalled example of large scale water harvesting. Today we continue the tale, highlighting the beautiful and practical Kuttam Pokuna, or Twin Pools, found at Anuradhapura in north-central Sri Lanka.

The Twin Pools at Anuradhapura

The massive reservoirs you saw last time allowed for more in antiquity than just growing rice. In this instance, two large granite pools were created and supplied with water from a rainwater-fed reservoir three kilometres away via an underground pipe (most water transfers in these systems were by open on-ground channels, but this one was different). It is believed the smaller, northern pool was constructed in the 8th century AD, and the larger one in the 10th.

The purpose of the pools? Well, there were, at the time, 5000 monks living here at Abhayagiri Monastery, in an area of about 500 acres. 5000 monks needed to stay cool, and needed to bathe, just like the rest of us. There were about twenty pools in the area, but only two were positioned right next to each other, and these were also the most elaborate and beautiful.

The water from the pools was recycled – feeding rice paddies nearby, which in turn fed the monks.

On the waterline on the far side, just to the right of dead centre of the image,
you can make out an exit drain. This one drain bled the water from both pools
– and into neighbouring rice paddies.

And, before it got this far, water entering the pools went through a clever filtration system that ensured the monks weren’t wading in impurities.

A three kilometre pipe emptied into the filter shown here in the foreground, via the
hole you can see at far right. Water needed to reach a certain height (about 12 inches)
before it could progress to the next chamber, leaving heavier-than-water items behind
where they could be periodically scooped out. Even the centre chamber – the final
one before entering the pool, had a raised exit pipe, as you can see.

A five-hooded cobra, considered a guardian of water, protects the inward
flow at the northern end of the northern pool (next to the filter).

So, many centuries ago, we had harvested rain water being transferred very accurately, via pipes made of eco-friendly materials, and used to service man’s recreational and hygiene needs – before emptying out into ‘the garden’.

There really is nothing new under the sun.

Follow up with:



  1. Thanks for the great article on ancient elegant design and engineering.Does the system still operate? I really enjoy and find most valuable articles that share the inspiration and solutions from old cultures and systems. The pictures are great too!

Leave a Reply

Your email address will not be published. Required fields are marked *

Related Articles

Check Also
Back to top button