The reservoir's filled by two pumpstacks that draw from separate breaches in top of the aquifer. The actual breach channeled down, not a channel to a breach in a wall. I plan to add more stacks when I'm not managing other tasks in the fort as i need to go dowsing (aka digging random channels down) to find out just how big the aquifer is. It seems to be a pocket of water in the hill, rather than the layer kind i keep hearing about.
Right now, I'm looking at points where i can add a few more exit channels so i can get more water pressure out. I have that partially-finished channel in the earlier picture now done and controlled with floodgates (thanks to some careful digging and quick lever-pulling). If anyone else wants to grab the save and suggest some good locations (I'm considering the north side, or just sticking another channel on the level above the new one), it'd help. The aim of the whole device is to push goblins and whathaveyou away from the entrance and down the east mountainside as quickly as possible. (Preferably "Hey Goblin, what that rumbling sound? You think Shortfolk tap magmaaaaaagaghhh?!!??! *flushed down the hillside*", but I'd settle for "to arms.... uh-oh, we seem to have trouble going forwaaarrrrrrddssss *flushed down the hilside*")
Here's the latest save -
http://dffd.wimbli.com/file.php?id=4987The schist lever in the reservoir control room (F1, then look just south of the reservoir for the room with all the levers) releases the water from the new channel above the front entrance.
Oh, and the reservoir's also SwordThunder's suicide device. If you look at the level above the control room, you'll see a small sealed-off furnished bedroom with The Lever in the center. Pulling that will flood the fortress corridors and any room with an open door if everything becomes utterly screwed.