Even if everyone practiced all the local green reforms, but the human population kept growing, the mass of people would overwhem everything. So along with green technology and green lifestyles, we should give every woman the legally protected right to decide if and when to conceive and birth her children, which most often results in no more than 1, 2 or 3 children per family. Then, as the human population reduces, the big cities will shrink to towns and villages and their water will come from nearby brooks and creeks, plenty for the smaller population.
A relentlessly growing population will eventually demand more water than the biosphere can provide. A smaller and stabilized population will have all the water it needs.