The Salt River Project plans to cut river water levels flowing into the Valley by 90 percent compared to this week's peak flows, a spokesperson said.
The cut, planned for no later than Saturday morning, will curtail flows from the Granite Reef Dam, north of Mesa.
Water that flows from Granite Reef forms the Salt River, which flows into Tempe Town Lake and then through central Phoenix.
Flows peaked earlier this week after heavy rain fall.
The reinvigorated Salt River collapsed part of Gilbert Road north of Mesa this week.
Repair plans will be drafted when the river dries up, a Maricopa County Department of Transportation spokesperson said.
Downstream from Tempe Town Lake, the Salt River is normally a dry river bed through central Phoenix.
The rain-fueled river this week washed away Isaac Russell's home, who lived along the river bed with his girlfriend.
"It's not the easiest, but you get by," Russell said.
He has been homeless for three years after kicking a heroin habit and losing his job.
This week's pop-up river washed away Russell's family photos and important documents from a camp near 19th Avenue, he explained.
His old tent is twisted around tree limbs at a former camp just downstream from Tempe Town Lake.
"We just want somewhere where we can be left alone," Russell said.
An SRP representative said crews fly over river beds before water releases to check for river bed dwellers. SRP did not know of any such people before the recent releases, the representative said.
The river bed is marked as off limits, with trespassers subject to prosecution.