Hydropower is great. Pumping water back "up the hill" for another pass through a circuitous swale system (ie a space filling curve) is also a good way to recyc

Hydropower is great. Pumping water back "up the hill" for another pass through a circuitous swale system (ie a space filling curve) is also a good way to recycle nutrients. When compared to the embodied energy of fertilizer I think you'll come out ahead.