Hand Digging Swale in Tanna Island, Vanuatu.

Part of the design we are working on in MAA International School in Middle Bush , Tanna Island, Vanuatu was the construction of water harvesting swales to capture and infiltrate water runoff to establish food forests and grazing pasture around them.

After researching the cost of hiring heavy machinery to do the  work we opted to hand dig the swales, 150m in total for the two swales.

The process started by surveying the contour, using a dumpy level, which was a good experience for the locals, it gave them an idea that this is actually not rocket science and they can all do this on their own plots

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The 150m took us three days to finish, with 10-15 people digging for 5-6 hours a day.

 

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The swale was 1m wide and 75cm deep , we put two level sill spillways on each swale as emergency over flows to allow big surges of water out as an insurance to preserve the integrity of the swale.

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The swale mounted was planted with Singapore daisy, and underneath the food forestry started, we planted cassava, taro, banana pigeon pea and as the fruit trees in the nursery will mature they will go into these food forests.

Water was also directed from the road by digging a trench from the road towards the swale, directing any runoff from the road through two small banana circles to slow down the water before it hits the swale.

As the system matures, and the water infiltrates underground recharging the aquifer and providing water for the food forests as they get established, the whole ecosystem will benefit with more consistent springs throughout the valley as it used to be before the chopping down of the forests for grazing cattle 50 years ago.

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