You raise several important questions at the end of your prompt, and I feel that the answer we have for these questions will define what kind of future will we have. You ask how can be fight water scarcity, and what steps should we take, asking if we should use technology, law, and the difference between developed and developing nations. I feel that dividing the possible solutions is a short sighted mistake, we must address the water crisis from all angles, and with all tools at our disposal.
But before we go out into the world trying to solve the water crisis we must take a hard look at our country. In a large scale, the existence of a city like Las Vegas, for example, is an inexcusable situation. In a smaller scale, it is unacceptable that he largest crop in the United States is grass. Yes, grass! More than corn, wheat and fruit trees combined!
We have a long ways to go with the water crisis we are in, and we better hurry up. Because once we run out, it is not going to be a pretty sight.