Georgia Water Resources Conference

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Georgia Water Resources Conference

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Georgia Water Resources Institute

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Indicators of Long Term Hydrologic Change in the Flint River

(Georgia Institute of Technology, 2013-04) Golladay, Stephen W. ; Hicks, David W.

The occurrence of three substantial climatic and hydrologic droughts since 1998 has raised concerns about water supply and stream flow throughout Georgia. This concern is acute in the Flint River Basin where low flows of unusual duration and magnitude were observed. The Flint River is essentially unregulated, originating just south of Atlanta and joining the Chattahoochee River to form Lake Seminole in southwestern Georgia. In addition to being an important water supply, the Flint River is noted for its biological and habitat diversity. For our analyses we used long term daily flow records from four stations (USGS: 02344478 – Griffin, 02347500 – Carsonville, 0234750 – Montezuma, 02353000 – Newton) to examine potential changes in hydrologic characteristics. We compared the period of 1940-1974 to 1975-2010, with the later period representing extensive development and population growth in the upper basin, and expansion of irrigated agriculture in the lower basin. Trends in rainfall were compared over the same intervals. No long term changes in annual rainfall were observed. Cycles of above and below average rainfall were observed as were periodic multi-year droughts. Annual water yields (annual CFS/watershed area at the station) ranged from 1.0 to 1.6 CFS/mi2 at all stations during most years. A declining tendency was observed at each station during the 1975-2010 interval, but was only significant at the Montezuma Station (p = 0.04). Winter yields showed similar declines only being significantly lower at the Griffin Station (p = 0.05). Summer yields were lower at all sites and significant declines were observed at Griffin, Carsonville, and Newton (p < 0.05). Calculation of 32 hydrologic indicators showed that the frequencies of low June-September median monthly flows, 1-day, 3-day, 7-day, and 30-day low flows were more common in the 1975-2010 interval at all stations. Our results indicate that human water use is causing increased severity and duration of low flows during the spring and summer seasons throughout the Flint River. These tendencies are pronounced during seasonal and extended droughts. Increased demand is the result of population expansion in the upper basin and irrigation expansion in the lower basin. Current rates of water use are likely unsustainable and pose a significant threat to stream health and the unique biological diversity characteristic of the Flint River.
Hydrologic Monitoring of a Hardwood Encroached, Isolated Depressional Wetland, Southwest Georgia

(Georgia Institute of Technology, 2007-03) Clayton, Brian ; Hicks, David W.

Hardwood encroachment into isolated depressional wetlands may change their hydrologic function. To gain a better understanding of this process we installed 12 shallow wells (5-12 ft. deep), in December 2005, on 2 transects crossing a 2.2 acre wetland in southwest Georgia. From March to October 2006, we collected hourly data in the wells and the wetland. Soil boring data showed that soil permeability increased close to the wetland and decreases up-gradient in the catchment. The deeper sandy soils in the ecotone store water which may be hydraulically connected to the wetland. Daily diurnal fluctuations in the water-level of the shallow wells in the ecotone suggests that the vegetation may have an effect on the shallow groundwater.
Stream Flow Changes Associated With Water Use and Climatic Variation in the Lower Flint River Basin, Southwest Georgia

(Georgia Institute of Technology, 2007-03) Golladay, Stephen W. ; Hicks, David W. ; Muenz, Tara K.

In the 1970’s agricultural water use expanded rapidly in the lower Flint River Basin resulting from the introduction of center pivot irrigation technology. The rapid expansion has raised concerns about impacts on regional stream flows essential to support aquatic fauna. Using long-term stream gage records from the USGS and climate data, we analyzed trends in stream flow in two major sub-watersheds and regional patterns of rainfall from 1940 through 2004. We observed no change in annual rainfall but seasonality changed with winters being slightly wetter. Minimum flows showed substantial declines since the development of irrigation. We attribute altered stream flows to increased regional water demand however; the demand for water is also exacerbated by long-term variations in climate and rainfall distribution.
Nitrogen Chemistry in the Upper Floridan Aquifer in Wells on the Ichauway Ecological Reserve, Newton, Georgia

(Georgia Institute of Technology, 2003-04) Jenkins, Joanna C. ; Hicks, David W.

Between May 2001 and May 2002, water chemistry was measured in groundwater at four well sites on the Ichauway Ecological Reserve. Water samples were collected weekly from the wells and analyzed in the Jones Ecological Research Center analytical laboratory for a suite of inorganic constituents. Well 1 was the only well that regularly contained measurable levels of ammonium-N that ranged from 0 to 21mg/l. Well 1 was also found to have elevated levels of nitrate-N that were about 2-4-fold higher than at the other well sites. Well 2 showed an increase in nitrate-N during the period of study while well 3 showed a decrease. In addition, chloride concentrations were found to be higher in well 1 than the other wells. Overall, ambient water chemistry reflects a portion of the Upper Floridan Aquifer that is minimally impacted by human activities. Wells 2-4 have near historic background concentrations of nitrate-N, and are relatively unaffected by nitrate-N contamination. However, levels of nitrate-N in well 1 are above historic background values suggesting some impact of human activities on nitrogen chemistry in this portion of the aquifer. Further studies are needed to determine the source(s) of elevated nitrates (intensive livestock production, widespread application of nitrogen fertilizers, or wetland depressions), and whether relatively pristine portions of the Upper Floridan aquifer, such as those found underneath the Ichauway Ecological Reserve, will experience higher levels of contamination in the future.
The Effects of the 2000 Drought on Freshwater Mussels in the Lower Flint River Basin

(Georgia Institute of Technology, 2003-04) Golladay, Stephen W. ; Gagnon, Paula ; Kearns, Margaret ; Battle, Juliann ; Hicks, David W.

A drought during the summer of 2000 caused record low flows in the lower Flint River Basin (FRB) and many perennial streams dried or became intermittent. Pre-drought surveys conducted in 1999 allowed an assessment of the impact of the drought on mussel assemblages. During 2001, 21 stream reaches which had abundant or diverse mussel assemblages were resurveyed. Where possible, study sites were classified as flowing or non-flowing during the drought. Mussel abundance at sites classified as non-flowing showed significant declines (median value 80% decrease) compared to flowing sites (median value 5% increase). Generally, greatest declines in mussel abundance occurred in the mid-reaches of the major tributaries of the lower Flint River. Declines in mussel populations appear to be associated with unusual climatic conditions and increasing demand on the area streams and the regional aquifer system for irrigation water supply.
Hydraulic Characterization of the Upper Floridan Aquifer in the Chickasawhatchee Swamp, Southwestern Georgia

(Georgia Institute of Technology, 2003-04) Hicks, David W. ; Clayton, Brian

The Chickasawhatchee Swamp is an expansive palustrine wetland located primarily in western Dougherty, eastern Calhoun, and northern Baker Counties, Georgia, in the Dougherty Plain district of the Coastal Plain physiographic province. The Chickasawhatchee Swamp is underlain by a shallow carbonate aquifer that may have a pronounced effect on the hydrologic signature of the wetland. The Swamp likely functions both as a groundwater recharge area and as a groundwater discharge area for the Upper Floridan aquifer. In the wetlands, the shallow aquifer is overlain by poorly drained swamp-alluvial soils, however, in areas where erosion has removed the overburden the carbonate rocks that comprise the aquifer are exposed. Nine wells tapping the Upper Floridan aquifer were installed in a spatially distributed pattern over the western part of the Swamp. A conceptual aquifer framework was developed and single-well aquifer tests were conducted. Each well was pumped at a low, intermediate, and high pumping rate that ranged from about 5 to 60 gallons per minute to evaluate yield characteristics, well efficiency, and aquifer response. Test results indicate the transmissivity ranges from about 1,140 to 21,300 square feet per day over the study area. The calculated transmissivity did not vary significantly between the three pumping rates which indicates that aquifer response is linear and that low volume, single-well pumping tests conducted in small-diameter wells can be used to develop representative estimates of aquifer transmissivity.
Water Monitoring Network in the Chickasawhatchee Swamp, Southwest Georgia

(Georgia Institute of Technology, 2003-04) Clayton, Brian ; Hicks, David W.

The Chickasawhatchee Swamp, located in southwest Georgia, is a large wetland complex encompassing more than 30,000 acres. The Upper Floridan aquifer underlies this region and is a major source of water for Spring Creek; one of four inflow streams. Interaction between the creek and aquifer is complex and being studied. Wells have been installed at thirteen sites in the western part of the swamp. Groundwater levels are taken hourly and water quality samples are taken monthly. Two surface-water sites on Spring Creek and two depressional wetlands are also sampled for water quality. Groundwater levels varied between sites suggesting recharge and discharge zones. Surface-water samples taken from Spring Creek had concentrations of calcium, 50 to 60 mg/L, specific conductance, 0.270 to 0.320 mS/cm, and magnesium, 1.1 to 1.4 mg/L. These concentration ranges were the same as water samples taken from groundwater wells located along Spring Creek. As more data are collected, the swamp’s hydroperiod and surface water/groundwater interactions will be further understood.
Water Resources of the Upper Suwannee River Watershed

(Georgia Institute of Technology, 2001-03) Davis, Mary M. ; Hicks, David W.

Situated in rural, south-central Georgia, the Alapaha, Little, Withlacoochee, and Suwannee Rivers of the Suwannee River watershed are important resources for the economy and health of the region. Groundwater is also an important resource in the region, as the Upper Floridian aquifer provides water for domestic, agricultural, and industrial supply. Declining water levels in the Upper Floridian aquifer in the northern part of the watershed, however, are indicative of overuse. Hydrologic monitoring is sparse in the watershed and studies conducted in other parts of the state, such as in the Flint River watershed, do not necessarily provide data or interpretations that are applicable to the Suwannee River watershed. Studies are necessary, therefore, to understand interactions between surface water and groundwater in this watershed and to develop effective regional water management strategies.
Impacts of Conventional Agricultural Practices on Aquifer Water Quality: An Overview of the Plains, Georgia Water Quality Study

(Georgia Institute of Technology, 1997-03) Bosch, David D. ; Leonard, Ralph A. ; Truman, Clint ; West, Larry ; Hicks, David W.

Pesticide leaching to groundwater is a potential problem in agricultural production areas of South Georgia where sandy soils predominate. The aquifers in this region are an important resource for South Georgia and North Florida. High soil hydraulic conductivity, coupled with high water-table conditions and high precipitation, can lead to groundwater contamination in the area. A field study near Plains, GA, was initiated in 1988, with the objective of establishing a better understanding of agrichemical transport in this area. Data was collected from 1988 to 1994 on a 0.81 ha research plot. Data indicate under normal climatic conditions nutrient and pesticide transport to groundwater is minimal. However, high precipitation soon after chemical application, combined with a saturated root zone, can lead to groundwater contamination Thus, extreme care must be used to properly manage the application and soil-water regime. Chemical application during periods of excess precipitation and saturated soil-water conditions must be avoided.
Characterization of a Crystalline-rock Aquifer Near Lawrenceville, Georgia: Application of Advances in Borehole and Surface Geophysical Methods

(Georgia Institute of Technology, 1997-03) Chapman, Melinda J. ; Hicks, David W. ; Peck, Michael F. ; Tharpe, W. Todd

A resurgence in the exploration of ground-water resources is evident as the population in northern Georgia continues to grow at a rapid pace and the demand for water supplies steadily increases. The need to apply accurate investigative methods to fractured-rock aquifer characterization is essential to any ground-water development program. The U.S. Geological Survey, in cooperation with the city of Lawrenceville, Ga., initiated a study in December 1994 to apply various investigative techniques to field characterization of a crysalline-rock aquifer near Lawrenceville. Interpretations of fracture strike were made from directional borehole radar surveys, acoustic televiewer logs, and surface square-array azimuthal resistivity surveys. Subsurface geophysical interpretations of fracture strike correlate with surface structural geologic data.