Final answer:
Thermoelectric power generation uses the most water in the United States, with agriculture being a major global user. Efficient irrigation and water conservation are key for sustainability.
Step-by-step explanation:
The process that uses the most water in the United States is thermoelectric power generation. Significant quantities of water are utilized for cooling in power plants, far surpassing the water used for other purposes including agricultural irrigation, industrial processes, and public use. Agriculture remains a major user globally, consuming around 70% of water used by humans, but in affluent countries like the U.S., industrial water use for energy demands often surpasses agricultural water consumption. Water conservation strategies and the development of more efficient irrigation systems are critical in areas where water is scarce to ensure the sustainable management of this vital natural resource.