What happens to the water after it sublimates, though? On Earth, evaporated water stays in the system and just comes back down as rain. You can recycle it over and over.
What happens to water vapor on Mars? Is it lost for good once it's exposed to the atmosphere? If you can't recycle it, then Martian water ice won't support a large colony for a long time, without some kind of artificial recycling system, which may be prone to failure and leaking.