From The Pueblo Chieftain (Chris Woodka):

More than 86 percent of the water diverted from the Arkansas River in Colorado goes to agriculture, but in some counties the rate is much higher. Even though water supplies have been depleted by urban transfers, irrigated agriculture is the mainstay of water use in the Arkansas Valley.

El Paso and Pueblo counties are the population centers of the basin, and water usage reflects the need to supply cities and power companies. In El Paso County, only 20 percent of water withdrawals are used for agriculture, while 41 percent of the water used in Pueblo County goes to farms, according to published estimates by U.S. Geological Survey. But in the four counties east of Pueblo, about 99 percent of the water that is diverted irrigates crops. About 250,000 acres of land have been irrigated, on average, over the past five years under the largest ditches and wells east of Pueblo…

“If you take the water off the land, you get grass and weeds,” [John Schweizer, president of the Catlin Canal and Arkansas Valley Super Ditch] said. “This year, the grass Aurora planted on the Rocky Ford Canal looks dead. This part of the country is not equipped to handle dry-land farming.”[…]

As it stands, about one-third of the farmland under the ditches east of Pueblo could eventually be dried up for other purposes — either because cities or power companies have purchased water rights or speculators purchased them with hopes of selling it to thirsty Front Range communities. Other large blocks of land were dried up after Kansas prevailed in a U.S. Supreme Court lawsuit on the point that Colorado irrigation wells were in violation of the Arkansas River Compact. A study last year by The Pueblo Chieftain showed 145,000 acres in the Arkansas River basin from Leadville to Holly could be dried up when water rights are fully developed. Figures from the Colorado Division of Water Resources show that 80,000 acres of farm ground already have been lost as water rights were transferred to cities, or well augmentation. More than 100,000 of the acres at risk are or were under the 20 largest canals east of Pueblo. Those canals at one time or another irrigated more than 300,000 acres. The canals today are unable to irrigate more than 50,000 acres in the Lower Ark Valley, mostly on the Colorado Canal and Rocky Ford Ditch, because Water Court decrees required drying up the land in order to remove the consumptive use of water — the amount once used to grow crops.