Georgia's 2013 Water Year: From Drought to Record Rain and Full Reservoirs

The U.S. Geological Survey's South Atlantic Water Science Center runs Georgia's long-term water monitoring network with local, state and other federal agencies: more than 340 real-time streamgages (10 of them measuring lake levels), 67 real-time surface-water-quality monitors, several water-quality sampling programmes and more than 180 groundwater wells, 39 reporting in real time. Hydrographers check the data through the year, and conditions are judged by comparing the current water year — October 1 to September 30, named for the year it ends — with the whole record. This fact sheet summarises the 2013 water year, October 2012 to September 2013.

Drought, then deluge

Drought had gripped the area since 2010 and carried into the 2013 water year. Then long spells of heavy rain arrived:

• In February 2013, for the first time since August 2010, no part of Georgia was in extreme (D3) drought on the U.S. Drought Monitor.
• Savannah recorded 9.75 inches of rain that February, its wettest February in 143 years of records; Macon and Columbus also set February records.
• In June, Augusta and Savannah had their wettest June on record.
• In July, rainfall statewide was 3.53 inches above normal.

Above-normal rain from February to September raised streamflow and groundwater and refilled lakes and reservoirs to full pool.

Runoff — flow per unit of basin area — is a good gauge of rain and streamflow in a basin. In the first quarter (October–December 2012) most of the state had below-normal, much-below-normal or record-low runoff. In the second (January–March 2013) above-normal rain brought most of it back to normal. In the fourth (July–September 2013) most of Georgia was above normal, much above normal or at record highs.

Streams

The sheet compares each stream's 2013 7-day average flow with its historical percentiles, and its daily flow with the record minimum, median and maximum.

Groundwater

Georgia has 15 of the roughly 130 wells in the USGS Climate Response Network, which tracks how drought and climate affect groundwater in shallow aquifers where pumping and other human influences are minimal. The wells shown have at least five years of continuous data, and each responds to the seasons much like a nearby stream — a sign that air, surface water and groundwater are linked.

• 07H003, Miller County (surficial aquifer, southwest). Below its historical median until February, when more than 10 inches of rain raised it 14 feet; it slipped below the median from March to June, then set new daily highs in July and August after more than 13 and 9 inches of rain.
• 16MM03, White County (crystalline-rock aquifer, northeast, where water sits in weathered rock and fractures). New lows of about 5.5 feet below land surface in late November and early December; after more than 7 and 12 inches of rain in December and January, new highs of 1.5 to 2.5 feet below land surface in January, April, May, June and July.
• 35P094, Chatham County (surficial aquifer, southeast). About 1 to 2 feet below the median at the start; more than 10 inches of rain in February raised it nearly 6 feet, and it stayed above the median for the rest of the year.
• 21T001, Laurens County (semiconfined Upper Floridan aquifer, east-central). New lows of 40 to 42 feet below land surface from October to February; more than 11 inches of rain in February raised it from 40 to 31 feet; above the median from May, with new highs in July, August and September after more than 8 inches of rain in July and nearly 7 in August.

Water quality

Water quality depends heavily on water quantity: rain and streamflow carry pollutants from both point and nonpoint sources.

Chattahoochee River near Fairburn (02337170), just south of Atlanta, drains 2,060 square miles. Its use is classed as "fishing" under Georgia rules, which require a daily mean dissolved oxygen of at least 5.0 milligrams per litre. It never fell below that in the 2013 water year. The USGS runs this and two other continuous sites, plus a long-term sampling programme, with the Georgia Environmental Protection Division, supporting its Clean Water Act work.

Around Atlanta, real-time monitors at streamgages — 15 in Gwinnett County, 8 in Fulton, 15 in DeKalb and 1 in Douglas — record temperature, specific conductance and turbidity, some also pH and dissolved oxygen. These can stand in for other measurements: specific conductance for dissolved solids, and turbidity for suspended sediment and what sticks to it, such as heavy metals, pesticides and fecal coliform bacteria.

On the Yellow River near Lithonia (02207120), draining 162 square miles in Gwinnett County, turbidity was measured continuously and 10 suspended-solids samples were taken, 7 in stormflow and 3 in base flow. Suspended solids and turbidity ran higher in storms, as runoff washed material off land and pavement into the stream; chronic suspended material is often what impairs streams. Specific conductance and dissolved solids were usually lower in storms, diluted by runoff, though some dissolved material does move at high flows.

Lakes and reservoirs

Georgia's major lakes are managed mainly by the U.S. Army Corps of Engineers and Georgia Power for water supply, flood protection, power, wildlife and recreation, using computer models that draw on real-time USGS streamflow.

• Lake Sidney Lanier, on the Chattahoochee, is the main drinking-water source for much of metropolitan Atlanta and the uppermost of a chain that includes West Point Lake, Walter F. George Lake and Lake Seminole. It hit its low for the year, 1,056.33 feet, on December 23, 2012; from January to April inflow was 3.6 times outflow, and the lake rose nearly 16 feet to full pool at 1,072.24 feet.
• West Point Lake, whose dam provides flood control and hydropower for Troup County, started about 10 feet below full pool and was raised 13 feet in December and January.
• Allatoona Lake, on the Etowah, stayed at or just below the top of its conservation pool all year.
• Hartwell Lake, uppermost of the Savannah River chain with Richard B. Russell and J. Strom Thurmond lakes, fell to 644.77 feet on December 15, 2012; with inflow twice outflow from January to April, it rose more than 20 feet to full pool at 664.79 feet.

Finding the data

The USGS no longer publishes annual data reports; current and historical data are on NWISWeb. WaterNow sends current data for a site by text or email on request, and WaterAlert notifies you when a site passes a threshold you set. Groundwater conditions are on Groundwater Watch.

Sources

• Knaak, A.E., Caslow, K., and Peck, M.F., 2015, Return to normal streamflows and water levels: Summary of hydrologic conditions in Georgia, 2013: U.S. Geological Survey Fact Sheet 2015–3024. https://pubs.usgs.gov/publication/fs20153024
• Tools: NWISWeb, WaterNow, WaterAlert, Groundwater Watch.
• Figures: U.S. Geological Survey, from the fact sheet's PDF (lake inflow and outflow data from the U.S. Army Corps of Engineers).
• Rewritten in hubnx's own words.