A list of questions I have about the Atlanta running-out-of-water situation. I pose them here, lazy-blog style, hoping someone out there knows the answer:
- to what extent does the Atlanta water supply have multi-year storage capabilities – to store extra during wet years for use during dry years
- what’s the relevant time scale for understanding drought in northern Georgia – one year? two years? five? ten? (this may simply be a different way of stating the above question about multi-year storage)
- what effect did the sustained dry periods of 1999-2002 or the extremely dry years of the 1980s have on water supply
- to what extent is groundwater used in northern Georgia
- what’s the breakdown of consumptive water use in northern Georgia between agriculture (is there any?) and municipal and industrial use
Paraphrasing the famous line from Chinatown, “It’s all Easter Island.”
My understanding of the facts about the Atlanta area water situation.
Most of the water consumed in the Atlanta area comes from Lake Lanier which is about 50 miles north of the airport.
It contains at full pool about 83 billion cubic feet of water.
Its current inflow (during the drought) is about 2 million cubic feet per day (CFD).
The 4 million Atlanta area users consume about 80 million CFD.
The C. of Engineers releases about 216 million CFD for downstream needs, such as fish, mussels and power plants.
There are about 90 days of water left before it is too shallow to provide outflow.
Please feel free to challenge the facts as I have pulled them from various local sources and either they or I could have messed them up.
Oops. Make the inflow in my last post 20 million CFD, not 2.
There is not much ground water in north Georgia. Atlanta lies in the Piedmont Province, characterized by “hard” rocks – intrusive igneous (e.g., granite) and metamorphic (schist, gneiss, etc.) rocks. These rocks don’t make good aquifers unless they are highly fractured. Even in that case, they don’t have much storage and are productive only if the fractures intersect a surface-water body. There are productive wells locally but nothing to supply Atlanta. I remember a 300-gpm well in an amphibolite aquifer in Fulton County; the “aquifer” had some huge fractures that interesected the Chattahoochee River. It was just sucking river water.
Once you get south of Atlanta and into the coastal plain, and some of the carbonate aquifers, you do have some good ground water sources.
Reservoir storage is limited. Unlike the West, which is more accustomed to drought and has large reservoirs (Mead, Powell, et al.) the Atlanta metro area has nothing like that. Lake Lanier is puny compared to what we are used to.
A colleague of mine once told me that the water supply systems of the East are geared (designed) towards being refilled every few years or so by large storms. If there is a drought for a few years, they are SOL.