Shaun McKinnon of the Arizona Republic explains the whole decision and history here. Plastic water bottles account for 20% of the overall waste at the Grand Canyon and 30% of the recyclable material. It's good that people are getting the message that they need to drink when they visit the Canyon, but the Grand Canyon is a fragile environment that undergoes heavy traffic. Limiting the number of plastic water bottles in the park helps keep trails clean, animals safe, and the views unmarred. All national parks are set to eliminate sales of water bottles within park boundaries, but each park is free to establish its own time and method for getting the bottles out. The Park Service plans to sell refillable bottles and provide water stations so visitors can still stay hydrated.