A Supreme Court ruling this week will make it harder for the Navajo Nation to get water from the Colorado River. No one disputes that century-old treaties give them a right to water flowing through their reservation. The court found that the federal government isn’t responsible for securing that water for the 170,000 tribal members who live there. It’s a win for Arizona, Nevada and California. They said requiring them to accommodate the Navajo Nation’s needs would upend negotiations over water supplies for 40 million people and a $15 billion-a-year industry that grows most of the nation’s winter vegetables.