A few people have said things like “do we think there is enough water for X?”.

Water level sensors are cheap and can run on a trivial amount of power, similar to the clock on the radio or microwave, which are always on.

I could build something like this 'indefinite' weather station by using

• a min/max detection is you just want auto-pump on/off (you'd make sure it was daytime, of course): food grade water level detection
• ultrasonic level detection like this video if you wanted to know the actual level at any point in time and not just 'did it fall below the min?'