Success! The dam at SplashCanyon is finished!
Was quite messy when the snows melted an my artificial lake started filling, with dwarves starting to fish at the bottom (despite the entire lake being a Restricted Zone with maxed out cost), and it ended with one baby drowning. Not that I care, had too many of those freeloaders anyway, so no big loss. The parents don't seem to care.
I now started project #2, constructing a fine balcony/statue garden a couple of levels below the floodgates that drain the dammed-up lake into the canyon, to get a nice waterfall effect added to it. Went fine, no troubles digging it out and furnishing it. I filled it with statues, gathered my dwarves for the grand unveiling, and opened the floodgates.
Question: Do you know what happens when you open two floodgates at the bottom of a four z-level deep lake? You how a toilet looks like when you flush? Yea, same thing here.
The water level in the lake dropped two z-levels in the blink of an eye (and, mind you, this is a pretty big lake), and before I realized what was happening, my balcony statue garden was quite heavily flooded due to, I'm guessing, the fact that there was more water than could "fit" falling down the cliff, so it started going wherever there was room. I closed the floodgates in time to avert disaster though, but my lovely balcony is now covered in mud... I think I need to adjust my dam design a bit...