Rather then make my farm one Z-level below, I decided on the ridiculously obtuse method of mining to a water source, building a channel, then pumping it out. This was purely for aesthetics, of course. I did this early in my fortress, when both dwarves and stone was a rarity, as my miner started out with zero skill and everything to prove.
The water source in question was a murky pool, which I gathered was just enough to make my tiny plot; this was not my main fortress, but a temporary one until I could mine out a deep, permanent location. Things proceed fine, and finally I put a floor over the downstairs to the water besides the pump after the wall was removed. It was about 3 or 4 water deep down there, but I hoped it was enough.
I assemble the pump, and then turn on 'start manually pumping'. Nothing happens. How strange, thinks Zauren. I check the dwarf in question who actually was an accomplished pump operator immigrant. This was his time to shine. Turning it on and off randomly and rebuilding the pump, he still never came to use it. Annoyed, I pick an arbitrary second dwarf. He also never comes to pump. I begin to think there might be a bug somewhere, and ignore the pump for awhile.
A season later, I really need that farm, and wish I had just freaking made it a Z-level lower. Before I do massive reconstructing, I order a third random dwarf to operate the pump. A miracle, he immediately runs over and floods the area. I prepare the fields, move on.
Then I get a frightening message: Give food canceled: No food. My stocks are at zero! I butcher what livestock I have. It takes me a little bit to ponder. Wait, give food? Who was trying to give food to what and why? I have zero injured dwarves. Having only about 12 total, I zoom to each one by one.
...And in the water channel, beneath the staircase that had a floor built over it TWO SEASONS AGO, I find a pair of dwarves. The pump operator, and the dwarf I had tried to make a pump operator. They had each run down there to grab a piece of stone. They were chest-deep in murky water, and had awful thoughts about drinking bad water amongst other things.
It seems that for months and months, my dwarves have been throwing food down the open channel behind the water pump to feed them while they were trapped. Given I have no reason to look one Z-level down, I completely missed them. I had them released, and one of them years later is now the Mayor.
I am mostly surprised dwarves will throw food down a hole a Z level to another dwarf. I didn't know they did that. But if I hadn't momentarily run out of food, I would of likely found those dwarves after they went insane instead from lack of booze. Luckily, neither of them sued.