Would it overflow?

Question

I'm in need of lots of water (and power :)), but I'd like to eliminate fun and seeing how water always gets me (I love water; my dwarves less so) I thought I'd ask here before building.

1. Top left: Ignore
2. Bottom center: Pump stack
3. Top right: Reservoir

The reservoir continues 5z up and down. Below the reservoir there's a small (12x2 tiles) basin for my dwarves to fish from, like so:

_________
-> wwwwww|
    |wwww|
    |wwww|    ______
    |wwwwwwwwww -> to water dump

If I were to glitch pump water to the top would it overflow the basin? FYI, the water dump channel is rather small (1x1 channel) and enlarging it is incredibly dwarfy inconvenient.

Answer 1

It could overflow. It depends how quickly the water can leave the basin to the water dump.

If the basin isn't full and the water always has somewhere to flow, everything will be fine. The water will flow through the basin and into the water dump. This does assume the water dump actually leads somewhere of course.

If, however, the water can't escape fast enough, water pressure will cause fun. Water pressure means that water in a system will rise to make everything level, even if it flows around a U-bend (as you've done. The water will continue to flow into the basin and the basin will overflow, flooding the room above.

For safety, you may want to add an emergency shutoff switch or pressure plate if it does overflow so you can shut off the pumps.

Answer 2

Not only do diagonal openings reduce pressure, but fortification tiles work the same way. Water (and magma) will flow through a fortification tile or diagonal opening, and in both cases the pressure drops so that any water passing through this form of 'pressure constrictor' won't ever rise higher than the z level of the diagonal or fortification.

In your design, any water that exists in the reservoir on a z level above your fishing area can potentially flood the fishing area since you don't have a pressure constrictor in the design. The only thing preventing flooding is your drain to the water dump that potentially allows any flood water to leave faster than it can overflow. If the drain becomes plugged (or is too small/slow), fun will ensue.

On the other hand, if you wish to train your fishing dwarves in swimming, you might adapt your design to allow some water to flood the fishing area but add sufficient drainage on the far side of the fishing area so it doesn't flood completely. Allowing 4/7 to 6/7 deep water to flow across an area your dwarves stand in teaches them to swim. 7/7 water will just make them drown unless they are already good swimmers. If you do this, build floor-grates across the drains so your dwarves don't get washed down the drain with the escaping water.