Final answer:
The region of the U.S. that uses the most water for irrigation is the Southwest, where farmers utilize extensive irrigation systems to grow a variety of crops.
Step-by-step explanation:
The region of the U.S. that uses the most water for irrigation is the Southwest. In arid regions like California and Arizona, farmers apply vast amounts of irrigation water to grow a variety of crops. Elaborate systems of dams, canals, and pumping facilities allow for highly productive and profitable farmlands.