red51 said on steam that perpetual water spring sources for forever distance would not be implemented, but might be able to figure out how to do distance limited. Nobody should be getting their hopes up of mountain springs flowing to streams to ponds to creeks to lakes to rivers to ocean. At best I would expect it to be useable for yard decoration and garden irrigation. Water flow algorithms are very expensive.
Problems to tackle after al the rest of trello is implemented, i think. In the meantime we will manage.
The idea of irrigation like it happend for thousands of years is good. I like building the old way with a very simple plumbing if needed; but thought more on plumbing for modern houses and waterdrainsystems on the roof that collects water in the barrels. A lot of people like to build modern structures 
It would make already a great difference if object collision is present for water in the game; that's enough for simple plumbing or prevent water to flow in a building standing in the sea or a lake. 