gravity feed irrigation
 

Any kind of gravity feed system is going to require some sort of
recirculation if you want it to automate itself. Otherwise as they go
down, they always empty out. And where they empty out will saturate
that area. If that's what you want, trough at the top of the entire.
Put feed lines to specific places. Dam around those spots and let the
rest just runoff to an uncared about area.