We will only see the comet lovejoy every 622 years, that doesn't suggest it's a problem at all, let alone a big one. The fact that the water levels are very low suggest there's a big problem, that we haven't seen them this low in 400 years suggests only that we've seen them this low before and that the world has survived that.
The planet isn't going to die if we irradiate ourselves into caves, but that doesn't mean irradiating the surface of the planet for shits and giggles is a good idea.
I think it depends on when the record keeping of the event began. So in this case if they started keeping records 250 years ago and they haven't experienced this level of drought since then, then it is considered record breaking. It doesn't mean that there haven't been worse droughts say, 300 or 400 years ago. It just means that either the official record keeping doesn't go that far, or that there may not be scientific research available to show that worse drought did occur before the the record keeping began.
I get that.
But clearly there are records there, records etched into stone in fact, that show that these events have occurred previously. That everyone turns this point into climate change denial is ridiculous.