Lake Allatoona is a U.S. Army Corps of Engineers reservoir in Georgia, located in northwestern metro Atlanta. Red Top Mountain State Park is located on its shores, on the peninsula between the Etowah and Allatoona arms of the lake. Allatoona also supplies much of the drinking water for the three counties it is in. The lake is supplied mostly by the Etowah River, and its major tributary the Little River (which joins the lake at Bell's Ferry), and in turn Noonday Creek. The other major arm of the lake is Allatoona Creek, extending down to Acworth, where pre-existing Lake Acworth now empties directly into Allatoona at Lake Acworth Drive (Georgia 92). Other significant streams include Kellogg Creek and Rose Creek.
The Allatoona Dam holding back the lake was completed in 1949 on the Etowah, which in turn merges into the Coosa River downstream (northwest) at Rome. The basin upstream (mostly northeast) of Allatoona covers about 1,100 square miles. This is nearly as large as the basin of Lake Lanier (Atlanta's biggest water source), but since the Allatoona is smaller, it drains and fills more rapidly than Lanier during droughts and floods.
The lake's summer level has averaged 840 feet above mean sea level. During major droughts it has dropped as much as 13 feet below this, exposing old tree stumps and former hills which are normally submerged at depth safe for navigating boats. Its maximum capacity or flood stage is +23 feet [863 feet AMSL (Above Mean Sea Level], though it has never been known to reach this level, and flooding of boat ramps and other lakeside facilities begins to occur well below it.
Hydroelectric power generation at Allatoona returns more than $3.5 million to the U.S. Treasury annually.
The Corps of Engineers has 662 campsites on Allatoona.