Water used for industry is still going to be used regardless of who controls that industry. Poor people can be just as greedy as rich ones, they just don’t have a means to act on it.
Population growth has slowed but it has not stopped. Even at 1 or 2 % per year it will be only a few generations before it becomes an issue. 1% of 6,000,000 people is a lot more than 1% of 600,000.