Let's nitpick then. It says: "According to its website, it is the largest underground network of pipes (2,820 kilometres (1,750 mi))[3] and aqueducts in the world.".

It could concievably have no pipe longer than 114 km.

Also if it's underground it's not a river?

That's a heck of an aquifer. Libya is pumping 2.4 km^3 a year from the estimated 150,000 km^3 reserve.