Special Thanks to the AJC for this story!

A regional water supplier’s efforts to still draw its current amount of water from Lake Allatoona comes down to two arguments: math and ownership of the water.

In a letter to the Army Corps of Engineers, the Cobb County-Marietta Water Authority disputes a claim by the corps that it is taking too much water from the lake.

The corps, which operates Allatoona and Lake Lanier, notified the regional water supplier earlier this month and gave it 10 days to respond. The authority is the primary wholesaler for Cobb and Paulding counties and sells water to other agencies in much of the northern suburbs.

It filed its letter late Monday night, after failing to win an extension on the deadline. Its chief point is that the corps only regulates how much water stored in Allatoona belongs to the authority; the state controls how much it withdraws.

The letter makes five other points:

• The corps claim that the authority is taking out more than the permitted 34.5 million gallons per day fails to take into account that about one-third of the water is returned to the water basin for use downstream.

• The corps has known since 1981 that the Cobb authority’s gross withdrawals exceeded the 34.5 million gallons per day, the level set by the corps.

• The authority’s water use is not adversely affecting other downstream users.

• The authority has no other options to meet water supply demands of its retail customers.

• The authority’s conservation programs are superior to other water users who draw from the same water source.

Officials at the corps said Monday night they would not respond immediately to the Cobb letter. They did not return calls for comment on Tuesday.

“We still didn’t totally agree with their math,” said Glenn Page, director of the Cobb County-Marietta Water Authority, on Tuesday.

Under a contract signed by the authority and the corps in 1963 and updated twice — in 1971 and 1981 — the authority pays to withdraw up to 34.5 million gallons of water a day from Allatoona, averaged over a year. The maximum it can take in one day is 58 million gallons.