USGS Science⌕ Search

Geology topics

Research about Georgia

Source-linked reports with geographic coverage including Georgia.

At least 397 records · Page 22Linked to original sources
USGS1994

Effects of urban flood-detention reservoirs on peak discharges in Gwinnett County, Georgia

The effects of flood-detention reservoirs on peak discharges along downstream reaches in six urban drainage basins in Gwinnett County, Georgia, were studied during 1986-93 using the U.S. Geological Survey's Distributed Routing Rainfall-Runoff Model (DR3M). Short-term rainfall-runoff data were collected at selected stations in six urban drainage basins in Gwinnett County. The basins range in size from 0.10 to 0.37 square miles and contain from 15- to 35- percent impervious areas. Each basin contains from two to six flood-detention reservoirs. The DR3M was calibrated using short-term rainfall-runoff data collected (1986-92) at each station. The model then was used to simulate long-term (1898-1980) peak discharges for these stations for conditions representing various amounts of detention ranging from the existing condition with all flood-detention reservoirs in place to the natural condition with no reservoirs. Flood-frequency relations were developed from the simulated annual peak discharges for each of these conditions by fitting the logarithms of the annual peak discharge data to a Pearson type III distribution curve. The effect of each flood-detention reservoir on peak discharges downstream was determined by comparison of peak discharges simulated with and without the flood-detention reservoirs. The cumulative effect of all flood-detention reservoirs in a basin on peak discharges downstream was determined by comparison of peak discharges for a flood with a given recurrence interval simulated with and without the reservoirs. Results of these comparisons indicate that removal of an individual flood-detention reservoir during simulations changes peak discharges from - 1 to 24 percent for the 2-year recurrence interval, from - 1 to 27 percent for the 10-year recurrence interval, and from -2 to 31 percent for the 100-year recurrence interval. The cumulative effect of removing all of the reservoirs from each of the six basins during simulation increases peak discharges from 1 to 38 percent for the 2-year recurrence interval, from 1 to 37 percent for the l O-year recurrence interval, and from 3 to 31 percent for the 100-year recurrence interval. In this study of six basins, several factors influenced the effect of flood-detention reservoirs on peak discharges downstream. The contributing drainage area, the maximum storage capacity, the outflow-structure capacity, and the elevation-to-storage relation of the flood-detention reservoir affected peak discharges in several basins. The location in the drainage basin and number of flood-detention reservoirs affected peak discharges in some basins.

Georgia↗
USGS1994

Effects of urban flood-detention reservoirs on peak discharges and flood frequencies, and simulation of flood-detention reservoir outflow hydrographs in two watersheds in Albany, Georgia

This report describes the effects of flood-detention reservoirs on downstream peak discharges of two urban tributaries to Kinchafoonee Creek (tributaries 1 and 2) in Albany, Georgia and presents simulated flood-detention reservoir outflow hydrographs. Rainfall-runoff data were collected for six years at two stations in these two urban watersheds. Tributary number 1 basin has a drainage area of 0.12 square miles, contains 23.8 percent impervious area, and contains two detention reservoirs. Tributary number 2 basin has a drainage area of 0.09 square miles, contains 12.9 percent impervious area, and has one detention reservoir. The Distributed Routing Rainfall-Runoff Model (DR3M) was calibrated using rainfall-runoff data collected during 1987- 92 at each station. DR3M was then used to simulate long-term (1906-33, 1941-73) peak discharges for these stations for conditions ranging from the existing condition with all detention reservoirs in place to the condition of no detention reservoirs. Flood-frequency relations based on the long-term peak discharges were developed for each simulation by fitting the logarithms of the annual peak discharge data to a Pearson type III distribution curve. The effect of detention reservoirs on peak discharge data to a Pearson type III distribution curve. The effect of detention reservoirs on peak discharges was determined by comparison of simulated flood-frequency peak discharges for conditions with and without the detention reservoirs. The comparisons indicated that the removal of flood-detention reservoirs from the tributary number 1 basin would increase the 10-, 50-, and 100-year peak discharges by 164 to 204 percent. Removal of the reservoir from tributary number 2 basin would increase these discharges by about 145 percent.

Georgia↗
USGS1993

Toxicity of sediments and pore water from Brunswick Estuary, Georgia

A chlor-alkali plant in Brunswick, Georgia, USA, discharged >2 kg mercury/d into a tributary of the Turtle River-Brunswick Estuary from 1966 to 1971. Mercury concentrations in sediments collected in 1989 along the tributary near the chlor-alkali plant ranged from 1 to 27 μg/g (dry weight), with the highest concentrations found in surface (0–8 cm) sediments of subtidal zones in the vicinity of the discharge site. Toxicity screening in 1990 using Microtox ® bioassays on pore water extracted on site from sediments collected at six stations distributed along the tributary indicated that pore water was highly toxic near the plant discharge. Ten-day toxicity tests on pore water from subsequent sediment samples collected near the plant discharge confirmed high toxicity to Hyalella azteca , and feeding activity was significantly reduced in whole-sediment tests. In addition to mercury in the sediments, other metals (chromium, lead, and zinc) exceeded 50 μg/g, and polychlorobiphenyl (PCB) concentrations ranged from 67 to 95 μg/g. On a molar basis, acid-volatile sulfide concentrations (20–45 μmol/g) in the sediments exceeded the metal concentrations. Because acid-volatile sulfides bind with cationic metals and form metal sulfides, which are generally not bioavailable, toxicities shown by these sediments were attributed to the high concentrations of PCBs and possibly methylmercury.

Georgia↗
USGS1993

Aerobic and anaerobic degradation of a range of alkyl sulfides by a denitrifying marine bacterium

A pure culture of a bacterium was obtained from a marine microbial mat by using an anoxic medium containing dimethyl sulfide (DMS) and nitrate. The isolate grew aerobically or anaerobically as a denitrifier on alkyl sulfides, including DMS, dimethyl disulfide, diethyl sulfide (DES), ethyl methyl sulfide, dipropyl sulfide, dibutyl sulfide, and dibutyl disulfide. Cells grown on an alkyl sulfide or disulfide also oxidized the corresponding thiols, namely, methanethiol, ethanethiol, propanethiol, or butanethiol. Alkyl sulfides were metabolized by induced or derepressed cells with oxygen, nitrate, or nitrite as electron acceptor. Cells grown on DMS immediately metabolized DMS, but there was a lag before DES was consumed; with DES-grown cells, DES was immediately used but DMS was used only after a lag. Chloramphenicol prevented the eventual use of DES by DMS-grown cells and DMS use by DES-grown cells, respectively, indicating separate enzymes for the metabolism of methyl and ethyl groups. Growth was rapid on formate, acetate, propionate, and butyrate but slow on methanol. The organism also grew chemolithotrophically on thiosulfate with a decrease in pH; growth required carbonate in the medium. Growth on sulfide was also carbonate dependent but slow. The isolate was identified as a Thiobacillus sp. and designated strain ASN-1. It may have utility for removing alkyl sulfides, and also nitrate, nitrite, and sulfide, from wastewaters.

Georgia↗
USGS1993

Recent growth increases in old-growth longleaf pine

Longleaf pine ( Pinus palustris Mill.) tree-ring data were obtained from an old-growth stand located in Thomas County, Georgia. The tree-ring chronology from the pine stand is composed of a collection of cores extracted from 26 trees ranging in age from approximately 100 to 400 years. These cores were prepared, dated, and measured, and the resulting data were examined with dendrochronological and statistical techniques. Beginning in approximately 1950 and continuing to the present, annual increments of all age classes examined in this study have increased, resulting in an average annual ring increment approximately 40% greater in 1987 than in 1950. When compared with expected annual increment, the increase for 100- to 150-year-old trees is approximately 45%, while the increase for 200- to 400-year-old trees is approximately 35%. In terms of stand-level aboveground biomass accumulation, the increased growth has resulted in approximately 5% more biomass than expected. The increased growth cannot be explained by disturbance; stand history; or trends in precipitation, temperature, or Palmer drought severity index over the last 57 years. Increased atmospheric CO 2 is a possible explanation for initiation of the observed trend, while SO x and NO x may be augmenting continuation of this phenomenon.

Georgia↗
USGS1993

Geochemical reconnaissance of the Carroll County Gold Belt and southwestern part of the Dahlonega Gold Belt, western Georgia

The gold deposits in the Carroll County gold belt and the southwestern part of the Dahlonega gold belt are in interlayered metasedimentary and metavolcanic rocks of Late Proterozoic to early Paleozoic age. These rocks are in several thrust sheets that form the southwest continuation of the Blue Ridge thrust stack. The rocks are now mostly mica gneiss and schist, graphitic schist and phyllite, quartzite, amphibolite, and granite gneiss. A sample suite of 788 rock and saprolite samples was collected; the suite represents most of the rock types exposed in the southwest extension of the Dahlonega gold belt in Cherokee, Cobb, Bartow, Paulding, and Haralson Counties, Ga., and in the Carroll County gold belt in Carroll and Douglas Counties, Ga. The samples were analyzed semiquantitatively for 30 elements and quantitatively for gold, copper, lead, and zinc; some samples were also analyzed quantitatively for arsenic, mercury, and molybdenum. Whole-rock analyses were made on 27 samples of relatively fresh mafic rock. More than two-thirds of the samples are saprolite derived from mica schist and gneiss, graphitic schist, amphibolite, and quartzite, or vein quartz in saprolite. The samples were collected from roadcuts, surface and underground mine workings, and mine dumps. Of the samples collected, 78 percent of those from old mine areas and 13 percent of those from roadcuts contain gold at or above a limit of determination of 0.02 parts per million (ppm). Of those samples that contain detectable gold, 36 percent of the mine samples and 92 percent of the roadcut samples have less than 0.2 ppm gold. Gold is present in detectable amounts in some samples from all the major rock types that were sampled. Gold does not correlate consistently with the other elements in the data set. The few positive correlation coefficients greater than 0.50 are restricted to the smaller subsets of a few samples. Most of the old mine areas contain small resources of gold in saprolite and probably larger amounts of lower grade material in unweathered rock. The mineralized zones are generally about 5 to 100ft wide, but may be as much as 250ft wide. Many deposits are only 100 to 800ft long, but a few mineralized zones are longer; one is as much as 0. 75 mi long.

Georgia↗
USGS1993

Water, energy, and biogeochemical budgets investigation at Panola Mountain research watershed, Stockbridge, Georgia; A research plan

The Panola Mountain Research Watershed (PMRW), located in the Panola Mountain State Conservation Park near Stockbridge, Georgia has been selected as a core research watershed under the Water, Energy and Biogeochemical Budgets (WEBB) research initiative of the U.S. Geological Survey (USGS) Global Climate Change Program. This research plan describes ongoing and planned research activities at PMRW from 1984 to 1994. Since 1984, PMRW has been studied as a geochemical process research site under the U.S. Acid Precipitation Thrust Program. Research conducted under this Thrust Program focused on the estimation of dry atmospheric deposition, short-term temporal variability of streamwater chemistry, sulfate adsorption characteristics of the soils, groundwater chemistry, throughfall chemistry, and streamwater quality. The Acid Precipitation Thrust Program continues (1993) to support data collection and a water-quality laboratory. Proposed research to be supported by the WEBB program is organized in 3 interrelated categories: streamflow generation and water-quality evolution, weathering and geochemical evolution, and regulation of soil-water chemistry. Proposed research on streamflow generation and water-quality evolution will focus on subsurface water movement, its influence in streamflow generation, and the associated chemical changes of the water that take place along its flowpath. Proposed research on weathering and geochemical evolution will identify the sources of cations observed in the streamwater at Panola Mountain and quantify the changes in cation source during storms. Proposed research on regulation of soil-water chemistry will focus on the poorly understood processes that regulate soil-water and groundwater chemistry. (USGS)

Georgia↗
USGS1993

Water resources data, Georgia, water year 1992

Water-resources data for the 1992 water year for Georgia consists of records of stage, discharge, and quality of streams; stage and contents of lakes and reservoirs; ground-water levels; and precipitation quality. This report contains discharge records of 114 gaging stations; stage for 27 gaging stations; stage and contents for 18 lakes and reservoirs; water quality for 143 continuing-record stations; peak stage and discharge only for 101 crest-stage partial-record stations and 7 miscellaneous sites; water levels of 25 observation wells, and water quality for 1 precipitation-quality site. These data represent that part of the National Water Data System collected by the U.S. Geological Survey and cooperating State and Federal agencies in Georgia.

Georgia↗
USGS1993

Ground-water quality of the Upper Floridan Aquifer near an abandoned manufactured gas plant in Albany, Georgia

Manufactured gas plants produced gas for heating and lighting in the United States from as early as 1816 into the 1960's. By-products including, but not limited to, oil residues and tar, were generated during the gas-manufacturing process. Organic compounds (hydrocarbons) were detected in water in the upper water-bearing zone of the Upper Floridan aquifer near an abandoned manufactured gas plant (MGP) in Albany, Georgia, during an earlier investigation in 1990. Chemical analyses of ground-water samples collected from five existing monitoring wells in 1991 verify the presence of hydrocarbons and metals in the upper water-beating zone of the Upper Floridan aquifer. One well was drilled into the lower water-beating zone of the Upper Floridan aquifer in 1991 for water-quality sampling and water-level monitoring. Analyses of ground water sampled from this well did not show evidence of benzene, toluene, xylene, napthalene, acenaphthlene, or other related compounds detected in the upper water-bearing zone in the study area. Low concentrations of tetrachloroethane, trichloromethane, and l,2-cisdichloroethene were detected in a water sample from the deeper well; however, these compounds were not detected in the upper water-bearing zone in the study area. Inorganic constituent concentrations also were substantially lower in the deeper well. Overall, ground water sampled from the lower water-bearing zone had lower specific conductance and alkalinity; and lower concentrations of dissolved solids, iron, and manganese compared to ground water sampled from the upper water-bearing zone. Water levels for the upper and lower water-bearing zones were similar throughout the study period.

Georgia↗
USGS1993

Hydrogeology, water quality, and water-resources development potential of the upper Floridan Aquifer in the Valdosta area, south-central Georgia

Water quality in the Upper Floridan aquifer in the Valdosta, Georgia area is adversely affected by direct recharge from the Withlacoochee River. Water enters the aquifer along a short reach of the river where sinkholes have formed in the stream bed. The water receives little filtration as it recharges the Upper Floridan aquifer through these sinkholes. Naturally occurring organic material in the river provides a readily available source of energy for the growth of microbiota in the aquifer. Microbiological processes and chemical reactions in the aquifer produce methane and hydrogen sulfide as the water from the river mixes with ground water and moves downgradient in the aquifer. Humic substances associated with the organic material in the ground water in this area can form trihalomethanes when the water is chlorinated for public supply. To assess areas most suitable for ground-water supply development, areal distributions of total organic carbon, total sulfide, and methane in the Upper Floridan aquifer were mapped and used to evaluate areas affected by recharge from the Withlacoochee River. Areas where concentrations of total organic carbon, total sulfide, and methane were less than or equal to 2.0 milligrams per liter, 0.5 milligrams per liter, and 100 micrograms per liter, respectively, were considered to be relatively unaffected by recharge from the river and to have the greatest potential for water- resources development.

Georgia↗
USGS1993

Geology and ground-water resources in the Zebulon area, Georgia

The current (1991) surface-water source of drinking-water supply for the city of Zebulon, Pike County, Georgia, no longer provides an adequate water supply and periodically does not meet water-quality standards. The hydrogeology of crystalline rocks in the Zebulon area was evaluated to assess the potential of ground-water resources as a supplemental or alternative source of water to present surface-water supplies. As part of the ground-water resource evaluation, well location and construction data were compiled, a geologic map was constructed, and ground water was sampled and analyzed. Three mappable geologic units delineated during this study provide a basic understanding of hydrogeologic settings in the Zebulon area. Rock types include a variety of aluminosilicate schists, granitic rocks, amphibolites/honblende gneisses, and gondites. Several geologic features that may enhance ground-water availability were identified in the study area. These features include contacts between contrasting rock types, where a high degree of differential weathering has occurred, and well-developed structural features, such as foliation and jointing are present. High-yielding wells (greater than 25 gallons per minute) and low-yielding wells (less than one gallon per minute) were located in all three geologic units in a variety of topographic settings. Well yields range from less than one gallon per minute to 250 gallons per minute. The variable total depths and wide ranges of casing depths of the high-yielding wells are indicative of variations in depths to water-bearing zones and regolith thicknesses, respectively. The depth of water-bearing zones is highly variable, even on a local scale. Analyses of ground-water samples indicate that the distribution of iron concentration is as variable as well yield in the study area and does not seem to be related to a particular rock type. Iron concentrations in ground-water samples ranged from 0.02 to 5.3 milligrams per liter. Both iron concentration and well yield vary substantially over a relatively small area. Implementation and Verification of a One-Dimensional, Unsteady-Flow Model for Spring Brook near Warrenville, Illinois By Mary J. Turner, Anthony P. Pulokas, and Audrey L. Ishii Abstract A one-dimensional, unsteady-flow model, Full EQuations (FEQ) model, based on de Saint-Venant equations for dynamic flow in open channels, was calibrated and verified for a 0.75-mile reach of Spring Brook, a tributary to the West Branch Du Page River, near Warrenville in northeastern Illinois. The model was used to simulate streamflow in a small urban stream reach with two short culverts, one with overbank flow around the culvert during high flows. Streamflow data were collected on the reach during three high-flow periods. Data from one period were used to calibrate the model, and data from the other two periods were used to verify the model. Stages and discharges over the periods were simulated, and the results were compared graphically with stage and discharge data collected at 10 sites in the study reach. Errors in simulated stage and discharge were small except when debris, not represented in the model, clogged the culvert. The effects of changes in physical and computational model parameters also were studied. The model was insensit'lve to replacement of measured cross sections with interpolated cross sections, especially if the measured thalweg elevation was preserved. Variation of the roughness, slope, and length of the culvert over-bank section, as well as the chosen representative measured cross section, caused only slight changes in the simulated peak stage and discharge. Changes in the modeled culvert area caused large differences in the simulated highflows in the vicinity of the culvert, whereas simulated low flows were unaffected. At all flows, the misrepresentation of the culvert area caused the simulated water-surface elevations to deviate from the measured elevations, especially on the falling

Georgia↗
USGS1993

Geohydrology and evaluation of water-resource potential of the upper Floridan Aquifer in the Albany area, southwestern Georgia

In the Albany area of southwestern Georgia, the Upper Floridan aquifer lies entirely within the Dougherty Plain district of the Coastal Plain physiographic province, and consists of the Ocala Limestone of late Eocene age. The aquifer is divided throughout most of the study area into an upper and a lower lithologic unit, which creates an upper and a lower water-bearing zone. The lower waterbearing zone consists of alternating layers of sandy limestone and medium-brown, recrystallized dolomitic limestone, and ranges in thickness from about 50 ft to 100 ft. It is highly fractured and exhibits well-developed permeability by solution features that are responsible for transmitting most of the ground water in the aquifer. Transmissivity of the lower water-bearing zone ranges from about 90,000 to 178,000 ft2/d. The upper water-bearing zone is a finely crystallized-to-oolitic, locally dolomitic limestone having an average thickness of about 60 ft. Transmissivities are considerably less in the upper water-bearing zone than in the lower water-bearing zone. The Upper Floridan aquifer is overlain by about 20-120 ft of undifferentiated overburden consisting of fine-to-coarse quartz sand and noncalcareous clay. A clay zone about 10-30 ft thick may be continuous throughout the southwestern part of the Albany area and, where present, causes confinement of the Upper Floridan aquifer and creates perched ground water after periods of heavy rainfall. The Upper Floridan aquifer is confined below by the Lisbon Formation, a mostly dolomitic limestone that contains trace amounts of glauconite. The Lisbon Formation is at least 50 ft thick in the study area and acts as an impermeable base to the Upper Floridan aquifer. The quality of ground water in the Upper Floridan aquifer is suitable for most uses; wells generally yield water of the hard, calcium-bicarbonate type that meets the U.S. Environmental Protection Agency's Primary or Secondary Drinking-Water Regulations. The water-resource potential of the Upper Floridan aquifer was evaluated by compiling results of drilling and aquifer testing in the study area, and by conducting computer simulations of the ground-water flow system under the seasonally low conditions of November 1985, and under conditions of pumping within a 12-mi 2 area located southwest of Albany. Results of test drilling, aquifer testing, and water-quality analyses indicate that, in the area southwest of Albany, geohydrologic conditions in the Upper Floridan aquifer, undifferentiated overburden, and Lisbon Formation were favorable for the aquifer to provide a large quantity of water without having adverse effects on the groundwater system. The confinement of the Upper Floridan aquifer by the undifferentiated overburden and the rural setting of the area of potential development decrease the likelihood that chemical constituents will enter the aquifer during development of the ground-water resources. Computer simulations of ground-water flow in the Upper Floridan aquifer, incorporating conditions for regional flow across model boundaries, leakage from rivers and other surface-water features, and vertical leakage from the undifferentiated overburden, were conducted by using a finite-element model for ground-water flow in two dimensions. Comparison of computed and measured water levels in the Upper Floridan aquifer for November 1985 at 74 locations indicated that computed water levels generally were within 5 ft of the measured values, which is the accuracy to which measured water levels were known. Water-level altitudes ranged from about 260 ft to 130 ft above sea level in the study area during calibration. Aquifer discharge to the Flint River downstream from the Lake Worth dam was computed by the calibrated model to be about 1 billion gallons per day; about 300 million gallons per day (Mgal/d) greater than was measured for similar lowflow conditions. T

Georgia↗
USGS1992

Effect of membrane filtration artifacts on dissolved trace element concentrations

Among environment scientists, the current and almost universally accepted definition of dissolved constituents is an operational one-only those materials which pass through a 0.45-μm membrane filter are considered to be dissolved. Detailed laboratory and field studies on Fe and Al indicate that a number of factors associated with filtration, other than just pore size, can substantially alter “dissolved” trace element concentrations; these include: filter type, filter diameter, filtration method, volume of sample processed, suspended sediment concentration, suspended sediment grain-size distribution, concentration of colloids and colloidally-associated trace elements and concentration of organic matter. As such, reported filtered-water concentrations employing the same pore size filter may not be equal. Filtration artifacts may lead to the production of chemical data that indicate seasonal or annual “dissolved” chemical trends which do not reflect actual environmental conditions. Further, the development of worldwide averages for various dissolved chemical constituents, the quantification of geochemical cycles, and the determination of short- or long-term environmental chemical trends may be subject to substantial errors, due to filtration artifacts, when data from the same or multiple sources are combined. Finally, filtration effects could have a substantial impact on various regulatory requirements.

Georgia↗