Transfers from 1950 to the present could take water from nearly 150,000 acres out of 450,000 historically irrigated acres in the basin, The Pueblo Chieftain reported Sunday.
Its analysis included losses through direct sales of water rights to communities, speculators or power companies; loss of storage once used by irrigators; or by decreases in well water use either through shutdowns or augmentation.
It also reflected the ultimate outcome of water rights sales, rather than temporary leases to or from farms.
Not all the water from the sales is being used yet. Many of the water rights are conditional, and some have not yet been adjudicated in water court, The Chieftain reported.
For instance, the Pueblo Board of Water Works has purchased rights for more than 5,000 acres on the Bessemer Ditch, but nearly all of the water is expected to be leased back to farmers for 20 years.
A draft report for the Colorado Water Conservation Board projects a need for 862,000 acre-feet of consumptive use water annually to fully irrigate land that is expected to remain in production by 2050. It projected a shortfall of nearly 400,000 acre-feet.