While clean water is indeed limited to some extent, it's merely a question of "at what price can I obtain clean water." If the government allowed markets to work instead of fixing prices, then as clean water was used the local price of that water would rise, and entrepreneurs would figure out ways to bring new clean water in to make a profit.
If governments allowed markets to work instead of fixing prices, we would have a great percentage of our GLOBAL population that cannot pay for clean water DIE because of it. Oh wait, this is already happening. Your solution to this particular problem seems to me will make it worse.