I guess the survivors would have to agree that the gold represented an abstract value that can be traded for food, water, guns.
Do you know the Twilight Zone episode "The Rip Van Winkle Caper" where a thief who robbed Ft. Knox deliberately goes into a "suspended animation chamber" and wakes up 100 years later, banking on the fact he can now sell the gold without suspicion? But the world has become like a desert and water has become a much more valuable commodity. Gold is now worthless since they invented a process to manufacture it. In the end he dies of dehydration by the side of a highway while trying to trade a gold brick for water.
I'm confident that a process to manufacture water will occur, before a process to manufacture gold.
But clearly water will have high value in the most extreme doomsday scenario. Should we put together a plan to start hoarding water? Lot of practical issues you don't have to solve if you want to hoard gold, LOL
Or just move to Northern Ontario or Northern Minnesota, no shortage of water there.