Larry if you were dictator what would you do about the water shortage and the over abundance of people?
Yah, that's the real hard question, isn't it? If I had a good answer and the courage of my convictions I'd have tried for the position long ago.
To begin with I'd assess the situation. Even a dictator can't make a scarce resource so I'd assure myself the problem could not be solved by increasing supply.
I'd begin with the easy, humane stuff. Talking to people honestly, insisting on conservation, rewarding innovation, punishing waste. (I actually live in a small, isolated desert town with a community operated water system and a moratorium on new building caused by an unremedial limit on suppy so I know about these things).
I'm sure that won't be enough. Harder measures would be needed. Some sort of birth control. What sort? That would depend on how absolute my power was and, what people proposed as they realized the depth of the problem.
In a scarcity situation what you would be trying to avoid at all costs would be all out war. A repetition of WWII with modern weapons would destroy humanity. Of almost equal importance would be a sudden collapse. You wouldn't want people to wake up one morning to find that the water supply system had collapsed completely and whole sections of the population had no water at all...unless you were militarily ready to enforce mass death by drought.