Where exactly is the Lake Lanier Drainage Basin

In response to my previous post, Rahn wondered what areas fed water into Lake Lanier, and the other area lakes. This was in response to my saying that rain north of Huntsville, Alabama would help reduce the drought. I did a little digging to find out the answer, and it may surprise you. Lake Lanier is part of what is called the ACF river basin. ACF stands for Apalachicola-Chattahoochee-Flint, the three major rivers that ultimately drain down into the Gulf of Mexico in Florida. Lake Allatoona is part of the ACT river basin, whose initials stand for Alabama-Coosa-Tallapoosa. That basin also drains into the Gulf near Mobile, Alabama. The map below shows the boundaries of the two basins:

ACF and ACT River Basins

The brown part of the map is the ACT river basin, and the green and yellow parts are the ACF basin. The yellow portion is the part of the basin that drains into Lake Lanier.

According to the Lake Lanier Association, the Lanier watershed is 1,040 square miles. The watershed for the entire Apalachicola-Chattahoochee-Flint basin is approximately 20,000 square miles. So, Lake Lanier provides water storage for 5% of the ACF basin, but because it holds 65% of the reservoir storage capacity of the system, it is relied on for water during a drought such as the one we are in now. And, while the Lanier watershed may have slightly more annual rainfall than the rest of the basin, given its relatively small size, I don’t think that the additional potential rainfall makes that much of a difference.

So to sum up, it looks a little odd to me that the relatively small watershed of Lake Lanier, and therefore metro Atlanta, has to be relied on to support all the needs of Alabama and the mussels of Apalachicola bay. Given the huge area of the ACF basin, it seems that more reservoirs that fill from other parts of the basin should have been constructed to help bear the load.

To answer the other part of Rahn’s question, rain north of Huntsville isn’t going to directly help Atlanta’s drought. However, Northern Alabama and Tennessee are also suffering from the drought, it’s going to help the entire area pull out of it. Droughts tend to feed on themselves, expanding as more areas become parched and dry. So, reducing the drought’s overall footprint will ultimately help bring it to an end.

And for those of you wondering where all the rain is, it’s apparently still coming. The storm has turned into a slow mover, and we’re likely to get rain until Friday, although not all at once. That’s probably a good thing, since it will allow more water to be absorbed into the soil, instead of running off immediately.


2 Responses to “Where exactly is the Lake Lanier Drainage Basin”

  1. Atlanta Water Shortage » Georgia Drought » Blog Archive » Where the extra water from Lake Lanier goes. Says:

    [...] Lawrenceville Weather Blog has a great post that details the area of the ACF (Apalachicola-Chattahoochee-Flint) river basin, which feeds into [...]

  2. Greg Says:

    My guess is that the topography is what drives having so much storage in Lake Lanier. North Georgia is mountainous, so if you pick the right place, then you can store a bunch of water without innudating excessive land (and, when I was a kid, land there was relatively cheap). South Georgia is flatter, so your lakes tend to be much shallower, without as much storage. To get more storage in south Ga, you’d need some really big lakes.