Worldbuilding

Not exactly currency, more a form of barter. But yes, it's rare. The water plants from the hot North are the only way to harvest usable water, besides preserving what they have. They extract it from an underground ocean, that probably originates somewhere in Night (in the south), but nobody dares venture past the safety of Dusk.

This town is a mining town, so they barter water for mined goods. Within the town itself, they don't really have money.