I spent some time searching and I don't see where this has already been suggested - if this is a duplicate suggestion I apologize. I am not posting this in the "improved farming" thread because after reviewing that thread, I don't think this idea has anything to do with the topics discussed there, this is a very specific "quality of life" change request. This has nothing whatsoever to do with food productivity or anything like that.
The current implementation of bucket irrigation is excessively fiddly and not-fun. In order to get a sizeable area irrigated, the user sets an activity zone, and a random dwarf waters that zone, which generally will leave you with a 3x3 set of tiles that end up being watered; so that zone must be removed, and another created for the next area of 3x3 tiles, and so on. Since only one dwarf will handle each pond activity zone, to cover a large area, the common technique is to use many zones, which is a ton of onerous micromanagement.
It would be much less irritating to just designate an area of tiles to be irrigated, similar to how tiles are designated for mining or engraving; at which point, dwarves go and get a bucket, get water, and bring it to the designated tiles, which are then examined to see if they already contain mud or water. If a given tile is already watered or otherwise not suitable (blocked by object, whatever) then it is de-designated, perhaps with just a job cancellation message.
I'm not suggesting removing the pond activity zone mechanic that is already in place, because it has other uses (e.g. filling a well) but I think this would be a very nice quality of life improvement for the player. Again, I don't feel this has any connection to farm productivity or other matters.
It would make a lot more sense if the water didn't have to be dropped from a higher z-level. Also, perhaps this type of job could be limited to dwarves with the Grower labor enabled, perhaps as an option in the (o)rders menu ("All dwarves irrigate/Only growers irrigate/No dwarves irrigate").
Thanks!