Lowest height accepted for 30A Outdoor Fused Safety Switch for water well?
Read article 430.102 of the NEC for a description of why some well installations do not require a disconnect within sight of the motor. One of the examples used in describing the exception condition (a) is "submersible motors", which covers a lot of well pump motors. If you have a submersible, you don't need a disconnect at the top of the well, it can be elsewhere. If you have a jet pump or turbine pump where the motor is at the top, you do.

There is no general rule on minimum height, but there are several unrelated rules (mobile home and trailer pedestals, EV chargers, etc.) establishing 2ft from the ground as a minimum, so it's best to use that even though it doesn't apply. But if you are in a flood plain, you should pay attention to the "100 year event" level.