Irrigated agriculture remains the primary consumptive use of water in the United States; however, population growth, environmental needs and changing societal values are driving a reallocation of water away from agriculture. It is projected that, by 2030, 33 million additional people will be living in the western United States, requiring approximately 30 billion more gallons of water for consumption per year. In much of the semi-arid areas of the world, new water resources will be in limited supply, particularly if remaining watersheds, aquifers and streams are protected from additional withdrawals for crop or livestock production.