Center Pivot ??

Each tower is self draining although the drains should be inspected to make sure they are not plugged. There will be a few drain plugs at the low points of the well pipe next to the pivot to remove. Gearboxes should be checked for water contamination by just loosening the drain plug enough to make sure oil comes out and not water. The pivot should be parked either into or away from (parallel to) the prevailing winter wind to lower the chance of it being blown over. Power to the unit should be locked out to prevent vandals from starting it in the middle of winter which could be destructive, it happened to a neighbors pivot once and luckily he caught it in time, apparently he had some enemies. Most farmers park them in the best direction to deter thieves and vandals from messing with them. Here in Minnesota the prevailing wind in the winter is Northwest so you either point it that direction or Southeast.

My casual observation is they all have arched tubes per section which would allow draining at the supports. I'm sure it's wise for the owner to check them all as winter approaches. Should be plenty of time for that since they should be done working before harvest.

It depends on your water supply. Pumping from a pond, river, you need to get pipe out of the water and drain plus your pump will have pipe plugs to remove. If you have a well some drain down the well caseing and might some plugs to remove. Buried pipe will need to be pumped also. We use a transfer pump for that job.