The U.S. Army Corps of Engineers is reviewing a request from Georgia to again reduce the amount of water flowing down the Chattahoochee River from Lake Lanier.

The state wants the corps to hold as much water as possible in the federal reservoir, metro Atlanta’s primary source of drinking water.

In its letter to the corps, the state Environmental Protection Division is asking to reduce the amount of water flowing past Atlanta’s Peachtree Creek by 65 million gallons of water a day to 420 million gallons, from Nov. 1 through April 30. That’s a 13 percent reduction, and is roughly equivalent to the amount of water withdrawn every day from Lanier by Gwinnett County during the winter.

Three decades ago, the state set the original target of about 485 million gallons of water a day to protect the river’s health. The target was set at the juncture of Peachtree Creek, because that’s where metro Atlanta’s largest sewer systems begin discharging millions of gallons of treated sewage every day. Having enough clean water in the river is critical to dilute the discharges.

The Corps granted a similar request by the EPD from mid-March through the end of May, helping to raise the lake by three feet. The corps began releasing more water from Lanier into the Chattahoochee in June because water quality generally declines in warm-weather months when dissolved oxygen levels plummet.

Sally Bethea, executive director of the Upper Chattahoochee Riverkeeper, opposes the reduction unless the local or federal governments install a real-time monitor in the river at Peachtree Creek to ensure the lowered target is being met.