Thanks. I hope it works out!
You seem like you know what you're doing, but since you mentioned it:
If you're worried about leaks, you can use Nylog White on the threads. It's food rated and works for your liquid and co2 gas connections. In theory, it's also not supposed to harden and make your fittings impossible to unscrew.
Looks like 3/8" NPT Schrader valve connection to me, but I'm not an expert on the matter.
The Polyformer is a 3D printer filament extruder created for people living in 3rd world countries with limited access to affordable filament. It allows you to recycle PET plastic from beverage containers by cutting them into a ribbon and feeding the ribbon through a heated extrusion nozzle.
Not everything is irrigated. They showed areas that are only fed by rainwater.
I think the point is that the soil was swept away and the ground is impermeable so any rainwater flows into the river or evaporates rather than supporting plant life or replenishing the groundwater.