Agriculture uses much of the ground and surface water supply in the United States with around 42% of the withdrawals due to irrigation in 2015. In arid regions, irrigation allows for crop production and adequate soil moisture in humid regions when precipitation is lacking. Productivity and profit margins greatly increased in agriculture due to the technique of irrigation. More than 54% of US crop sales accounted for farms where some sort of irrigation technique was installed. Both surface water and groundwater contribute to the water supply used in irrigation. Surface water accounts for more than half of the water used in irrigation while the rest comes from groundwater.