Stina Sieg/KJZZ

The Gila River is a major tributary of the Colorado River that flows through parts of Arizona and New Mexico.

Monday night is the deadline to comment on a proposed federal rule change over so-called “Waters of the United States.” It could mean big changes for how some waterways are regulated.

The rule change re-defines which streams are covered under the Clean Water Act. In a change from the Obama Administration, the Trump EPA and Army Corps of Engineers would remove “ephemeral” streams from Clean Water Act protection. Those are streams that run in response to rain or snow.

Environmental and conservation groups are saying this is a big rollback of protections that took years to develop. Mining and development interests are happy with the change — they say it removes unnecessary permitting.

The deadline to submit a comment is 8:59 p.m. Arizona time.