Water managers from across the Colorado River Basin are preparing to negotiate new rules for allocating the river’s dwindling flow and sharing the pain of a deepening shortage.

They’re adapting the 100-year-old Colorado River Compact to a river that little resembles the bountiful gusher that negotiators from seven states and the federal government in 1922 thought — or hoped — would bless the Southwest forever. The stakes rise with every foot that Lake Mead and Lake Powell fall, as the states and the water users within them recognize they’re due for a tighter squeeze.