Extreme drought: Summary of hydrologic conditions in Georgia, 2012

Streamflow and Groundwater Data Daily Discharge and 7-Day Average Streamflow Conditions, 2011 Water Year

Chattooga River at Summerville, Ga. 02398000

The Chattooga River flows from the northwestern corner of Georgia into Alabama where it flows into Weiss Lake (U.S. Geological Survey, 1975). For the first half of the 2012 WY, 7-day average streamflow conditions were “normal” to “much above normal,” followed by “below normal” and “much below normal” streamflow for the latter part of the water year. Daily discharge in most of the first part of the 2012 WY was in the “maximum” range compared to historical data until February, when median daily mean streamflows were observed for most of the rest of the 2012 WY.

Ocmulgee River at Macon, Ga. 02213000

The Ocmulgee River flows out of Jackson Lake and joins the Oconee River to form the Altamaha River (U.S. Geological Survey, 1975). During the majority of the 2012 WY, the 7-day average discharge was “below normal” to “much below normal.” New record-low 7-day average streamflow conditions were observed in 2012 for the months of April, May, June, July, and September. New minimum daily-mean discharges were observed during the months of April, May, and September.

02213000 Ocmulgee River at Macon, Georgia

7-Day Average Discharge Hydrographs show the 7-day average for 2012 as compared to historical 7-day averages. Data are categorized in percentile ranges from “much above normal” (greater than the 90th percentile) to “much below normal” (less than the 10th percentile) (U.S. Geological Survey, 2012d).

Daily Discharge Hydrographs show 2012 daily-mean streamflow, in cubic feet per second, as compared to historical minimum and median streamflow for the entire period of record (U.S. Geological Survey, 2012a). Sweetwater Creek near Austell, Ga. 02337000

Sweetwater Creek is a major tributary of the Chattahoochee River (U.S. Geological Survey, 1975). The 7-day average streamflow fluctuated between “much below normal” and “normal” from October through March, and new 7-day average minimum record flows were recorded during latter part of the water year, in April, May, and July. New minimum daily mean discharges were observed during the months of April and May.

at US 84, near Quitman, Georgia

Withlacoochee River at US 84 near Quitman, Ga. 02318500

The Withlacoochee River flows in the Suwannee River Basin in the southern coastal plain of Georgia (U.S. Geological Survey, 1975). For much of the 2012 WY, 7-day average streamflow conditions were “below normal” to “much below normal,” and record-low 7-day average streamflows were observed during the months of January and February. New minimum daily-mean discharges were recorded during the months of October, January, and February. Normal flows were observed towards the end of the 2012 WY as much needed relief was provided during multiple tropical storm events.

02318500 Withlacoochee River Climate Response Network

The USGS maintains a network of groundwater wells to monitor the effects of droughts and other climate variability on groundwater levels. These wells are part of the Climate Response Network, which is designed to measure the effects of climate on groundwater levels in unconfined aquifers or near surface confined aquifers where pumping or other human influences on groundwater levels are minimal (U.S. Geological Survey, 2007, 2012c). The national network consists of about 130 wells, of which 15 are located in Georgia. These wells are monitored as part of the USGS Groundwater Resources and Cooperative Water Programs. Current conditions of groundwater wells in the Climate Response Network can be accessed online at http://groundwaterwatch.usgs.gov/.The hydrographs presented here are for selected wells in Georgia having at least 5 years of continuous data.

Well 07H003, Miller County

Well 07H003 is in Miller County in southwestern Georgia and is completed in the surficial aquifer, which is an unconfined aquifer in this area (Peck and others, 2013). The water level in this well generally rises rapidly during wet periods and declines slowly during dry periods. The water level in well 07H003 responds to seasonal change similarly to streamflow at the nearby streamgage on Ichawaynochaway Creek at Milford, Ga. (02353500), which indicates atmospheric, surface-water, and groundwater interactions. In the 2012 WY, water levels in well 07H003 were below the historical daily median from October through February. In March the area received more than 6 inches of precipitation and the water level in well 07H003 was greater than the historical median. Water levels were also above the historical median during the months of June, July, and August. Well 03PP01, Walker County

Well 16MM03, White County

Well 37P116, Chatham County Well 03PP01 is in Walker County in northwestern Georgia and is completed in the Paleozoic-Rock aquifer in the Chickamauga limestone. Water storage is in the regolith, primary openings, and secondary fractures and solution openings in rock (Peck and others, 2013). Water levels are influenced mainly by precipitation and local pumping (Cressler, 1964). The water level in well 03PP01 responds to seasonal change similarly to streamflow at the nearby streamgage on Lookout Creek near New England, Ga. (03568933), which indicates atmospheric, surface-water, and groundwater interactions. The water level in well 03PP01 was near the historical daily median for much of the first half of the 2012 WY and above the historical daily median from June through September.

Well 16MM03 is in White County in northeastern Georgia and is completed in the crystalline-rock aquifer. Water is stored in the regolith and fractures, and the water level is affected by precipitation and evapotranspiration (Cressler and others, 1983). Precipitation can cause a rapid water-level rise in wells tapping aquifers overlain by thin regolith (Peck and others, 2013). The water level in well 16MM03 responds to seasonal change similarly to streamflow at the nearby streamgage on Chattahoochee River at Helen, Ga. (02330450), which indicates atmospheric, surface-water, and groundwater interactions. The water level in well 16MM03 remained below the historical daily median during much of the 2012 WY.

Well 37P116 is in Chatham County in southeastern Georgia and is completed in the surficial aquifer. Water levels in this well generally rise rapidly during wet periods and decline slowly during dry periods. The water level in well 37P116 responds to seasonal change similarly to streamflow at the nearby streamgage on Peacock Creek at McIntosh, Ga. (02203559), which indicates atmospheric, surface-water, and groundwater interactions. The water level in well 37P116 fluctuated above and below the historical daily median during most of the 2012 WY.

Water-Quality Conditions in Georgia

Water-quantity and quality information are both important for ensuring adequate water availability for human consumption, industrial uses, and aquatic ecosystems. Precipitation and streamflow conditions are primary agents of delivery and transport of both pointand nonpoint-source-contaminants (Hirsch and others, 2006). The USGS provides the GaEPD and the public with a relevant, nationally consistent database of longterm water-quality data, which assists the GaEPD in meeting its responsibilities under the Clean Water Act, including (1) identifying the beneficial uses of surface waters within the State, (2) establishing water-quality standards to maintain the full beneficial uses of surface waters, and (3) identifying water bodies where stream standards are not met and beneficial uses are impaired (Grams, 2011). The USGS-GaEPD discrete water-quality sampling program is designed to collect data systematically, regardless of hydrologic conditions. Water-quality data for Georgia streams are available to the public at http://waterdata.usgs.gov/ga/nwis/qw/.

Figure 6.

Coosa River station 02397530, located on the border of Georgia and Alabama and is in the Coosa-North Georgia planning region, has a drainage area of 4,362 mi. Water use for this stream reach is classified as “fishing” under the Georgia Code 391-3-6-.03, which requires that the daily mean dissolved oxygen (DO) concentrations in the stream be equal to or greater than 5.0 milligrams per liter. This figure shows daily mean DO and water temperature WT for the 2012 WY and median values for the period of record (1975 –2011) for this site. Typically, DO and WT are inversely related, as indicated by data for the period of record at this site. From March through August of the 2012 WY, however, DO increases as WT increases. The DO increase may have been caused by phytoplankton growth, which can lead to algal blooms. Water-quality at this station is influenced by fluctuations in water level and water velocity because of regulation at Weiss Lake and resulting backwater conditions; inflows of municipal and industrial wastewater from upstream facilities; and hot-water releases from power generation plants. During the 2012 WY, no daily mean DO levels fell below the “minimum DO” criteria at station 02397530. Chattooga River station 02177000, located in northeastern Georgia in the Savannah-Upper Ogeechee water planning region, which has a drainage area of 207 square miles (mi). A number of pH measurements were collected at this station during the 2012 WY; pH is a measure of how acidic or basic the water is and can influence the biological integrity of streams. For example, the reproduction of some fish can be affected in water having a pH below 5 (U.S. Geological Survey, 2012c).

Flint River at Newton station 02353000, located in southwestern Georgia in the Lower Flint-Ochlockonee water planning region, has a drainage area of 5,740 mi. A number of specific conductance (SC) measurements were collected at this station during the 2012 WY. SC is a measure of dissolved ionic constituents, such as salts in water. Throughout the 2012 WY, SC was typically lower during higher flows because dissolved constituents in streams can be diluted during rainfall runoff, as compared to lower flows.

Conasauga River station 02387000, located in northwestern Georgia in the Coosa-North Georgia water planning region, has a drainage area of 687 mi. During the 2012 WY, a number of total suspended solids (TSS) samples were collected and turbidity measurements made. Turbidity is a measure of water clarity and light reflected off particles in streamflow caused by clay, silt, and fine suspended inorganic and organic matter; therefore, TSS and turbidity react similarly during changing streamflow conditions. Chronic levels of suspended materials in streams are often the cause of designated use impairment. TSS concentrations and turbidity levels were typically greater during higher flows compared to lower flows because these constituents are washed from the land into streams during periods of rainfall runoff and suspended in the water column, demonstrating a relation between water quality and water quantity.

Figure 6.

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