So the Dwarfs of Udirurdim have pacified Cave2, and my Cave-Beast trap-maze is now fully functional (the new model includes in a "Magma Flush" feature, allowing me to scour FBs from the passages with fiery death). Unfortunately, many Dwarfs were lost during various stages of the cave pacification; most of them weren't even proper, instant deaths. A Dwarf was lightly injured, then hauled up to the hospital where he thirsted to death. Which brings me around to my question. Cave2 is an ideal level for my Dwarfs, excepting that it has only one pool of water, which is apparently tepid, because the Dwarfs won't take water from it.
Now, there are a couple of things I could probably do to make that water more appealing (or potable, for that matter), but I've got it into my head that instead I want to tap Cave1, a flooded cavern roughly 15 Z-levels above Cave2, and bring that water down for waterscaping and controlled flooding (we're going to terraaqua-form the whole cavern). Problem being - I'd like to have continuous flow from Cave1 to Cave2, this poses specific concerns related to waterborne pests such as Giant Toads and Cave Crocodiles - those are easily dealt with by a simple wall of grates, but more robust aquatic interlopers (FBs, for instance) post a building-destroying problem that renders grates ineffective.
Simply put, any suggestions about a way I could build a continuous flow channel that carried water down about 10/15 Z's (it doesn't have to go only down, U-bends might factor into the build somehow) and blocked the movement of all possible invaders from the upper cavern layer? As an aside, I have unlimited access to well-controlled magma.