One must wade through a thicket of bureaucratic jargon to find it, but on Friday federal officials issued what appears to be a serious warning to California and other states that use water from the highly stressed Colorado River: If they cannot agree on sharp reductions in diversions of the Colorado’s water, the feds will impose them unilaterally. It’s the latest wrinkle in decades of interstate squabbling over the river, which has become more heated as the river’s flows continue to decline and conditions in its two major reservoirs, Lake Mead and Lake Powell, reach the crisis stage.