Originally posted by GunsForBucks:

Keep in mind there is also a limit how far inland water will go... if your river was too long it wouldn't work. Think that is how it used to be.? Been a while since I tried.

Nope, water in valheim is at the same height globally. If you can dig down far enough (e.g. with the mod mentioned) you find water. The only water in valheim that can change level is tar pits.