The American Southwest has horribly mismanaged it's fresh water supply. Tulare Lake, Hoover Dam, and Las Vegas are just some examples of the American Southwest's horrible fresh water management. My suggestion is does the rest of the United States and North America have a right to the fresh water contained in the Great Lakes? Would a pipeline from Chicago to Los Angeles or Mexico City be better for the environment than a desalination plant?
As a person who lives in Los Angeles:
No :)
Most of our water usage is to grow fruits and vegetables especially since we have one of the longest growing seasons in the country and decently fertile soil in the Central Valley thanks to the river deposits from the Sierra Nevada. But because of the profit motive and Capitalism most of that food is stuff that is shipped thousands of miles away.
Urban usage is a drop in the bucket but its still important to conserve water wherever possible.