Hall County has received a letter of commitment from Forsyth County to purchase water from the future Glades Reservoir.

“For planning purposes only, Forsyth County anticipates having a potential need for between 20 and 40 (million gallons per day) of the reservoir yield for Forsyth County’s future use,” wrote Charles Laughinghouse, Forsyth County Board of Commissioners chairman, in the letter.

Though the letter was not a financial commitment, Laughinghouse said Forsyth County is “interested in entering into financial discussions with Hall County, including assistance in the upcoming costs of planning and permitting.”

The U.S. Army Corps of Engineers has granted Hall County officials additional time to revise their federal reservoir application and court potential buyers. The permit will be issued based on demand.

Forsyth is the first county to commit to buying capacity in the reservoir. The city of Gainesville, Gwinnett County and DeKalb County are also considering buying into the reservoir.

Glades Reservoir is planned on 850 acres in northeast Hall County with an elevation of 1,180 feet. Officials are estimating a 50 to 75 million gallon per day yield at this time.

Harold Reheis, a consultant for the Glades Reservoir and former director of the Georgia Environmental Division, said there are still many things up in the air.

“It is possible to make it bigger,” Reheis said. “The amount of capacity that both Hall County and Forsyth County will need is in part dependent upon what’s going to happen in the big picture with Lake Lanier.”

U.S. District Court Judge Paul Magnuson — looking at a decades-old struggle between Georgia, Florida and Alabama over water rights — ruled in July that Lake Lanier was not a federally-authorized source of drinking water.

He gave Georgia until July 2012 to make a deal with Florida and Alabama over the lake’s use or risk losing it as the main source of drinking water for most of metro Atlanta.

In the worst case scenario — that no drinking water may be withdrawn from Lake Lanier — “Forsyth County and Hall County are going to need all the water they can find,” Reheis said. “If that happens, even 75 million gallons per day will not be large enough for those two counties.”

But counties are primarily looking at the Glades Reservoir as a secondary water source.

Reheis said if withdrawals from the Glades Reservoir will be used to supplement current withdrawals, then 50 to 75 million gallons per day would satisfy the needs of the area.

“Other counties recognize the value of this,” said Tom Oliver, Hall County Board of Commissioners chairman. “It’s something where we can control our own destiny.”