The upper top left figure shows the interconnected nature of these ancient irrigation systems. At village level they form cascades and the water transfer from upstream to downstream is mostly through subsurface seepage rather than surface transfer.
The top right shows the general landscape of the Killinochchi area. Many of the reservoirs in this area were destroyed during a 30 year long civil war and most of the ancient irrigation tanks were not functioning or connected.
But as you can see from the Viswamadukulam tank where there are sufficiently large reservoirs with enough surface water storage, they replenish the groundwater and transform the whole eco system in the vicinity.
So how can we revive these systems.? We did a project with the irrigation department of Sri Lanka to develop what we called 'Mosaic Systems' which connected 140 ancient irrigation tanks to the left bank canal of a major new irrigation project. This was completed in 2014 and the joint management of water between the traditional distributed system with its retention and infiltration services operated by the community should provide us with sustainable agriculture systems that address both floods and droughts.
