Anachrony · Board game rules
Do I return the 1 water when a borrowed worker returns through time travel?
Quick answer
No, you don't return the 1 Water paid to warp the Worker in; it's already spent and gone.
Details
When you warp a Worker into the present during the Warp phase, you must pay 1 Water (or use Water that was warped in with that Worker). This cost is permanent—the Water is consumed as part of bringing the Worker through the Time Rift. [p.10 — Warp phase]
Later, when you use a Power Plant to shift your Focus back to a past Timeline tile where you have a Warp tile with that Worker, you may choose to send the Worker back through time. To do so, you spend the Worker from your Active column. [p.16-17 — Power Plant buildings: Time Travel and Focus] This represents the Worker being returned, but the 1 Water you paid to bring them forward was a one-time cost that doesn't get refunded.
Watch out: The rulebook notes that "these goods being spent are the very same goods you received in the past, seemingly 'for free'"—but the Water cost is the exception. It's a real cost paid in the present Era to enable time travel, not part of the asset loop. [p.17 — Power Plant buildings: Time Travel and Focus]