It was known as The Holocaust, which a Holocaust is where one group of people try to eliminate a certain group of people like how the Nazis tried to get rid of the Jewish people.
The answer is: Water management projects created huge reservoirs and lakes where there had been dry canyons.
The National Reclamation Act of 1902 was a federal law that was passed in order for the federal government to start major irrigation projects in the West.
The result of these major projects was the creation of complex structures and systems(reservoirs and lakes) that would allow for the transformation of arid lands into farm capable lands.