ScottB asked how much water pot takes, and frankly, I have no idea. But I know how to guess.
First, I hoped for an ETcrop (evapotranspiration is how water moves through the plant into the atmosphere). That’s a co-efficient that researchers have measured for all the major crops. You multiply it against a reference ET, which is how much water a reference crop uses. The California Irrigation Management Information System uses grass for its reference crop. Other systems use alfalfa. If you wanted, you could go to CIMIS and find out how much water a patch of grass transpired under each day’s weather conditions. Then you multiply that by the coefficient for your crop, and figure out how much water you should put on to re-fill the soil profile.
I didn’t hope to find an ETcrop for pot, but I did find one for a type of hemp. Under well-watered conditions, the seasonal average crop coefficient for Sunn hemp was 1. So Sunn hemp needs the same amount of water as a patch of grass. If pot and Sunn hemp are similar, pot has the same water demands as the reference grass for CIMIS.
All of that is thinking too hard. If you don’t know, guess 3.5 feet per year. Nod sagely and squint at the mountains in the distance. If someone gives you grief, say “but did you consider your salt flushing requirement?” Distract them with questions about their system’s filter capacity and ask when they last backflushed their filters. Tell them the manufacturer specs require more frequent backflushing and then quit the field victorious.