By Pam Knox
The current drought in Georgia has caused significant problems for farmers in central Georgia and other areas of the state, but a lack of impact on the state's larger cities and drinking water supplies has kept it off most Georgians' radar.
As of early December, 14% of the state was experiencing exceptional drought, drought that is only expected to occur every 50-100 years. This region was experiencing some level of drought during the entire 2012 growing season. Some areas are 20 inches below normal rainfall.
Drought is classified into four levels: moderate (D1), severe (D2), extreme (D3) and exceptional (D4) drought. A few areas in central Georgia have been experiencing extreme drought continuously since May 2011.
While wetter weather this summer alleviated drought in some areas of the state, drier-than-normal conditions have expanded due to a deficit of tropical rainfall at the end of the summer and a persistent high pressure system that has diverted storms away from the state. This year Georgia was largely bypassed by tropical systems.
This fall a strong high-pressure system steered rain-bearing systems away from the state and suppressed convective rain. The systems that would have usually brought rain to Georgia passed to the north of the state, resulting in a fall that was even drier than usual for the driest time of year.
More than half the state received less than half its usual rainfall in September, October and November, causing stream flows to drop to near-record levels and expanding the areas affected by drought.
One of the differences between the current drought and the drought of 2007-2009 is the location of the areas affected by the drought. In 2007 the center of the worst drought was in northern Georgia, where it affected cities like Atlanta and Athens.
The extremely high temperatures associated with that fast-developing drought and concerns about water supply and water usage helped to raise public consciousness about the severity of the drought and generated increased media attention.
By comparison, the current drought has affected a smaller part of the state with less effect on water supplies.
More of the state is being affected by drought now than at the worst periods of the 2007-2009 drought.
In the worst-hit areas, farmers have reported their farm ponds completely drying up — leaving nothing but cracked mud and fish bones behind — something they did not see in the 2007-2009 drought.
Groundwater levels in the lower Flint River basin are, in many cases, at or near record lows. Stream flows across the state have also been very low during the recent weeks except immediately after rain events.
The outlook for winter precipitation is uncertain. Originally, an El Nino weather pattern was predicted to occur this winter. This was excellent news, since El Nino is usually associated with above-normal-rainfall across Georgia. However, the El Nino fizzled early, and now we are in neutral conditions — with neither an El Nino nor La Nina present to steer storms towards or away from Georgia.
In neutral conditions, we know that the state is equally likely to receive normal, below normal and normal amounts of precipitation.
There is only a 33% chance of getting above normal rainfall based on statistics for neutral years. This means that spring soil moisture could be of critical concern to farmers, since germination and plant development depend on having adequate supplies of soil moisture.
Low stream flows and falling ground water levels, especially in the Flint River basin, could affect southwest Georgia farmers' ability to irrigate their fields in the coming months.
Soil moisture helps insulate soil from extreme temperature changes, so Georgia's currently dry soils may experience more extreme temperature changes in farmers' fields and could result in increased damage to plants.
- Pam Knox is the University of Georgia Agricultural climatologist and program specialist in UGA Department of Biological and Agricultural Engineering.