Matthew Staver for The New York TimesThe artist Christo at a meeting this month in Canon City, Colo. His display is expected to draw 400,000 visitors over two weeks. DENVER — The idea of a fabric-draped Arkansas River in southern Colorado, anticipated by many as art and dreaded by others as environmental degradation, has been postponed. The artist Christo, who has been working on the project, called “Over the River,” for more than 20 years, through a federal environmental impact study and uncounted rounds of public hearings and local meetings, said the earliest date for the completed installation is now August 2015, a year later than the most recent schedule. Uncertainties involving construction and permits made the delay necessary, but the continuing dialogue with Colorado residents was also a factor, the Over the River organization said Tuesday in a statement. “The public will have time to better understand how traffic, safety and other issues will be addressed,” the statement said. A spokeswoman for the main opposition group, called Rags Over the Arkansas River, known by its acronym, ROAR, said the delay would allow more time to marshal evidence, including the impact on bighorn sheep and other local wildlife, that the group says was underestimated by federal land managers. A federal lawsuit filed this month on ROAR’s behalf by a group of students from the Sturm College of Law at the University of Denver accuses the federal government of sloppy work in approving the plan last fall. “The delay will allow ROAR and other opponents to weigh in with key officials to express new concerns that we continue to find,” said the group’s spokeswoman, Joan Anzelmo, in an e-mail. The $50 million project, financed by the artist, includes eight suspended-panel segments totaling 5.9 miles along a 42-mile stretch of the river about three hours southwest of Denver. The seasonal 28-month construction schedule is to culminate in a two-week display that is projected to draw 400,000 visitors.