From The Pueblo Chieftain (Chris Woodka):
There are roughly 12,400 water rights in the Arkansas River basin, but only those that are absolute rights can be considered for abandonment. Conditional water rights, those that have not been fully put to use, must pass a due diligence test in Water Court every six years.
After an abandoned right has been listed — it is published on the state website and in local newspapers — the owners can protest with a written objection in Water Court. A judge makes the final decision. “Typically, there will be a few people who recognize that they own a right on the list and they will register a protest,” Witte said. “The majority have truly been abandoned.”
More Arkansas Basin coverage here.