To put it another way: if the users being asked to conserve water could just pay farmers to use their water, both would come out ahead. The farmers would get more value than from using it for farming, and the other consumers would get more water for a lower price than from alternatives.
In any case, it's bizarre you cringe at the word "markets". Societies that try to avoid markets are horror shows. Markets are an utterly essential social technology for the modern world.