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 [[https://community.element14.com/products/arduino/arduino-projects/b/blog/posts/weather-station-that-lasts-months| 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): [[https://www.amazon.ca/Optical-Infrared-Sensibility-Working-Controller/dp/B075R6SSHJ/ref=pd_day0fbt_d_sccl_2/133-1725566-5921435?pd_rd_w=OikFe&content-id=amzn1.sym.ff016894-f98c-4e04-9d48-02d33c57e482&pf_rd_p=ff016894-f98c-4e04-9d48-02d33c57e482&pf_rd_r=5385GT180M9PTMQQS6E5&pd_rd_wg=dSP9N&pd_rd_r=c3d7b478-145d-4f4c-a80e-e10064a32e30&pd_rd_i=B075R6SSHJ&psc=1| food grade water level detection]]
  * ultrasonic level detection [[https://www.youtube.com/watch?v=A2eSNBYnTao | 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?'