The Environmental Protection Agency has redefined which waterways are covered under the Clean Water Act, and how much pollution can be dumped into them.
The updated policy excludes some wetlands and all ephemeral streams -- which only flow after a heavy rain or intense snowmelt.
They act as tributaries to rivers that millions of people across the southwest count on for drinking water and irrigation.
In Colorado, about 70 percent of all streams will be affected by the new rule. In New Mexico and Nevada, it’s upwards of 90 percent.
Oil and gas companies, homebuilders and some agriculture groups cheered the change. Environmental groups and left-leaning states vowed to fight it.