I was going to PM waldronate, but in a moment of clarity I decided no to bother him, and instead hope that he will read this thread
The question is, is it possible to load into Wilbur a "rainfall map" so to speak, indicating the density of rain (on a grayscale map perhaps), so it can be used by the precipition-based erosion and river flow calculations?

If not, would you have any interest at all on implementing it? =)