The Colorado River has about 19% less volume than in the year 2000.

Researchers have quantified just how much water the agriculture industry in the Western U.S. is taking from the Colorado River, one of the most important river systems in the region.

More than half of the Colorado River's total annual water flow is being used to irrigate agricultural land, according to a paper published Thursday in Communications Earth & Environment.

Waters from the Colorado River have not reached its delta in the Gulf of California for more than 50 years because nearly every drop is being consumed as the waters flow south, Brian Richter, president of Sustainable Waters, a global water education service, senior freshwater fellow at the World Wildlife Fund, told ABC News.