0005966: An error in Aquifer placement code.

Dwarf Fortress Bug Tracker - Dwarf Fortress

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Date Submitted

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0005966

Dwarf Fortress

Dwarf Mode -- Environment

public

2012-05-28 21:07

2012-05-28 21:48

Reporter

Riloki

Assigned To

Priority

normal

Severity

minor

Reproducibility

always

Status

new

Resolution

open

Platform

Windows XP

OS Version

Product Version

0.34.10

Target Version

Fixed in Version

Summary

0005966: An error in Aquifer placement code.

Description

It seems that when placing aquifers it will check that there's an [AQUIFER] layer within a number of Z-levels from the surface. If one is found and the biome is one that contains an aquifer, it'll go down several Z-levels (I've been seeing between 3 and 5) and designate that layer an aquifer layer.

Any [AQUIFER] material on that layer will become an aquifer, as will any below it. That's fine. Except it does not check that there are any [AQUIFER] materials on the layer it selects. Therefor it is possible (and common) to have a 'ghost' aquifer, in which the site finder will report an aquifer, but one will not actually be available.

This was tested by turning all stone types into [AQUIFER]-possible materials after discovering that in areas of 'little soil' containing an aquifer, no aquifer will actually be found.

Steps To Reproduce

1) Gen a new world (I used a small region)
2) Go to site finder, search for Soil: Little, and Aquifer: Yes.
3) Embark on an area containing only one kind of biome containing the aquifer, and dig. (this is to ensure you are not merely missing the biome the aquifer is contained within)
3a) Please note I used DFHack's reveal function to double check I was not merely unlucky with my exploratory shafts.

Unless you dig into sandstone or conglomerate as your top stone layer, you will almost never actually encounter an aquifer, despite receiving an embark warning of one, and it being listed in the site finder.

Additional Information

I would propose this be fixed simply by finding the lowest aquifer-bearable material within its normal placement range, and placing it there, which would put it in line with real-life groundwater behavior.

If Toady felt particularly adventurous, he could even make there a chance for a 2 wide or more aquifer on areas with low drainage but high rainfall.