Well, actually, even on a small plot all the water can be harvested - from roofs and such. If not in tanks, at least in the soil. And all water can be used twice. First in the house, then on the plants. Compost toilets eliminate a lot of water usage, growing food in closed systems like aquaponics or grow towers use very little water and the food is not being shipped, packaged and all of that...
It is surprising what all can be done 😄