 Why does Joseph lie about the water supply?
"On account of the quantity, I'm able to quote a bargain price. Shucks, boys, it hurts me more to charge for water than it does for you to pay. "Just the same," Joe griped, "paying for water isn't something you can get used to in ten minutes." In the fragile forest, they soon came across a stream that sprang from the igneous soil and splashed into the small pond whose contents, according to the mayor, was theirs for the asking. Something shrewd was called for.... "Joseph!" "You'll find everything you want in the back room," Johnson said frantically, "sulfopyridine, mustard plasters, rubs, inhalers, suction cups—" "Relics of the past," Harvey stated.
 He wants people to believe they need to pay for it.
 There isn't a lot of water there, and he needs to be able to ration it out.  He wants people to believe they need to pay for it.  He wants to keep the fresh water for himself.  He thinks that people would prefer to buy filtered water.