I’m working on a story/gaming idea, and one of the premises may call for Mars to be terraformed, or at least partially terraformed.
Any idea where I could find out how big the oceans would be, etc.?
This is not as easy as it sounds… I may have bitten off more than I can chew.
Well, yes.
But the water would not stay in place all over the planet. Just like here, water will go downhill.
I know there are low points. I used to play SimEarth enought to know that Oceans would accumulate. The question is, how much and where?
Not all that deep (by earth standards) I think the last numbers I saw said 200m and mainly in the northern basin.
Looks to me like you want a topographic map of Mars. (Generated by the kewl MOLA project)
They talk about liquid water, and it looks like they even take into account the new water-containing South pole theory.
Personally, I’d take a look at this amazing, clickable Astronomy Picture of the Day and explore the sites related to it. (They’re listed underneath it) For the sake of reality, perhaps check into where they pulled their 0m mark from.
The logistics of current terraforming plans kinda depended on that CO2 for the greenhouse effect, but assuming you can get by that, it appears the “Hellas impact basin” would become the focus of a huge new beach-front real estate industry, and that ocean shipping would be restricted to the northern hemisphere. 
IIRC, a terraformed Mars would end up having one mega-continent and small islands spread throughout the oceans. I don’t remember if that continent would be in the northern or southern hemisphere, or straddle them.
And one MF of an island: Olympus Mons.
Hmmm… from the looks of that map, most of Northern Mars would become part of the ocean, with a possible Sea of Hellas in the newly ocean bound continent.
200m. Is that deep enough to support a decent biome of cold water ocean going creatures? Anyone?
Thanks for the help, I appreciate it.
Kim Stanley Robinson’s Mars trilogy goes into quite a bit of detail about what his theoretical coastlines would be.
Well continental shelves range from 30-300 m and the majority of sea life lives there. Take the Grand Banks as an example.