Reports state that since the start of the year Cheltenham has had over 210mm (7 inches) of rain and that was on ground that for the November meeting was officially soft and for the December meeting was officially good to soft (although all the hurdle race times were closer to soft ground).
With the course currently somewhere between good to soft and soft https://www.thejockeyclub.co.uk/cheltenham/owners-and-trainers/the-going/ there is absolutely no need to start watering because with the amount of rain we have had since the start of the year Cheltenham’s water table must be very high and as such it will not take main rain to halt the drying and revert the course back to soft.
If it was good ground all round and still drying out and little rain forecast then you could understand starting to water now to maintain that level but to start watering now is an absolute joke, as you only need the weather to throw you a curve ball forecast and then you are looking at potentially deep winter ground again (which we should only be getting if the weather intervenes).