By David Emory Stooksbury
University of Georgia
Georgia is entering the climatological summer. Climatologists define summer as June, July and August. This year’s astronomical summer, the summer solstice, begins June 21.
Drought conditions have already spread into south-central and southwest Georgia. Much of southeast and coastal Georgia is now abnormally dry for early June.
After improvements in drought conditions across north Georgia during the cool season, conditions are expected to worsen over the next several months.
Summer routinely brings temperatures in the 90s. Georgians can expect hot, dry weather to cause very rapid soil moisture loss over the next week. This loss in soil moisture will also drop stream flows and groundwater levels.
Several indicators are used in drought classification: 30 day rainfall, 90 day rainfall, 6 month rainfall, 12 month rainfall, 24 month rainfall, rainfall since the previous October 1 (the “water year”), soil moisture, stream flows, groundwater levels and reservoir levels.
Across much of south Georgia, 30- and 90-day rainfall has been well below normal. Thirty day rainfall over much of south-central and southwest Georgia has been less than half of normal. Some locations reported less than one-quarter of normal rainfall over the past month.
Ninety day rainfall across the southern half of the state has been generally less than 70 percent of normal with pockets in south-central and southwest receiving less than 50 percent of normal rain.
Stream flows across most of the state are currently just above the previous record-low flows for early June. Many of the current stream-flow records across the state were set in 1988 and 2007.
A few locations are setting daily records for low flow including the Chattooga River near Clayton, the Oconee River at Milledgeville, the Flint River near Oakfield and at Newton and the Withlacoochee River near Quitman.
Soil moisture levels are extremely low along and west of I-75 and along and north of I-20. With little rainfall and temperatures in the 90s, soil moisture levels which had been in relatively good shape for the remainder of the state have been dropping very quickly over the past couple of weeks.
Farm ponds, especially ponds not fed by springs, are starting to show the lack of rain. Many ponds didn’t receive adequate recharge during the winter and entered the summer already low.
Extreme drought conditions exist in Banks, Elbert, Franklin, Hart and Stephens counties of northeast Georgia. This means that multiple drought indicators are at levels that we expect about once in 50 years.
The counties north of a Carroll - Fulton - Clayton - DeKalb - Rockdale - Walton - Oconee - Oglethorpe - Wilkes - Lincoln counties line are classified as being in severe drought. This means that multiple drought indicators are at levels that we expect about once in 20 years.
Moderate drought is now found in the counties north and west of a Lowndes - Cook - Tift - Turner - Crisp - Dooly - Houston - Bibb - Jones - Baldwin - Hancock - Glascock - Warren - McDuffie - Richmond line. Moderate drought classification occurs when multiple drought indicators are at levels we expect about once in 10 years.
Mild drought conditions have developed in Ben Hill, Berrien, Bleckley, Bryan, Burke, Chatham, Echols, Effingham, Irwin, Jefferson, Lanier, Liberty, Pulaski, Twiggs, Washington, Wilcox and Wilkinson counties. Mild drought means that several drought indicators are at levels we expect about once in seven years.
The following seven southeast Georgia counties are currently classified as not being in drought: Appling, Bacon, Brantley, Glynn, Pierce, northern Ware and Wayne. However, soil moisture is decreasing rapidly in these counties. Drought conditions could develop over the next several weeks in these counties.
The remaining south Georgia counties are classified as abnormally dry for early June. Localized drought conditions are starting to develop in these counties.
Widespread drought conditions are expected in these counties within the next couple of weeks. Abnormally dry means that several drought indicators are at levels that we expect about once in five years.
For the next several months, Georgia’s best chance for widespread drought relief will be tropical disturbances. However, the tropics usually don’t become active until late summer.
June and July are critical. Without major rain events the soils will continue to become drier leading to lower stream flows, groundwater levels and reservoir and pond levels.
For current Georgia drought information, go to the Web site www.georgiadrought.org. Weather information is available at the University of Georgia automated weather station network Web site www.georgiaweather.net.
(David Emory Stooksbury is associate professor of Biological and Agricultural Engineering at University of Georgia's College of Agricultural and Environmental Sciences.)