Epanet is used to stimulate water flow and pressure loss (head loss) in a pipe network so you can design a pipe network that meets your water flow and pressure requirements. It probably can be used in a city game if that game has water distribution network component.

Yes, I mean precisely using it for simulating pipe network.

I love the idea of a SimCity type game with a ton of details. Having the level of detail of simulating a water distribution system is some dwarf fortress type detail. Make sure to also add a permitting office, building permit system, and HOAs that protest your building permits.

Or a more minimalistic, where you only focus on pipes and wires.

(Compare: Railroad Tycoon)