Georgia Water Resources Conference

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Georgia Water Resources Conference

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https://hdl.handle.net/1853/70886

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Georgia Water Resources Institute

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Now showing 1 - 10 of 10

Water Quality Dynamics in Lake Lanier

(Georgia Institute of Technology, 1999-03) Xiao-Qing, Zeng ; Rasmussen, Todd C.

We present a summary of water quality changes in Lake Lanier using data from 1966, 1973, 1991, and 1997. The data are used to characterize water quality variability a) at various locations within the lake, b) with depth below the surface, c) by season of the year, and d) over the thirty years of record. We focus on the physical, chemical and biological parameters related to nutrient cycling in Southeastern reservoirs, including temperature, dissolved oxygen, pH, Secchi depth, TSS, and turbidity, specific conductance and alkalinity, chlorophyll a and biomass, and nutrients. Changes with depth dominate changes along the lake for most parameters, and short-term seasonal changes dominate long-term changes at most sites.
In-Situ Monitoring of Suspended Sediments: Development of a Densimetric Monitoring Instrument

(Georgia Institute of Technology, 1999-03) Calhoun, Daniel L. ; Rasmussen, Todd C.

We present a new technique for continuously monitoring total suspended solids concentrations. Our approach is to use a differential pressure sensor to measure the fluid density within the water column. The fluid density is directly affected by the concentration of suspended solids, thus allowing us to infer the sediment concentration. Ten demonstration sites on the Broad River in northeast Georgia have been selected for comparing the densimetric technique with turbidity, grab samples, and integrated samples. Variations in sediment concentrations with stage, velocity, and temperature will be evaluated.
Daily Sediment Loads in the North Oconee River

(Georgia Institute of Technology, 1999-03) Cox, Bobbie ; Rasmussen, Todd C.

We present 65 years of daily turbidity data from the North Oconee River obtained from the Athens drinking water treatment facility. We use these data to characterize short- and long-term water quality changes from nonpoint sources. The turbidity data have been coupled with daily USGS discharge data for the Middle Oconee River to provide an estimate of the distribution of daily sediment loads for the period of record.
Characterization of Temporal and Spatial Variability of Turbidity in the Upper Chattahoochee River

(Georgia Institute of Technology, 1997-03) Holmbeck-Pelhaml, Skelly A. ; Rasmussen, Todd C.

Our objective is to develop the information necessary for establishing a regulatory basis for sediment control. We present sediment data at four USGS monitoring stations in the Upper Chattahoochee River Watershed. The data show that TSS is a strong function of discharge. A unique relationship between TSS and discharge is found for all stations when the discharge is normalized by its long-term mean. With this regional relationship, we can establish a baseline for comparing watersheds as a function of discharge.
Complex Variable Boundary Integral Modeling of Groundwater Flow and Transport

(Georgia Institute of Technology, 1997-03) Rasmussen, Todd C. ; Yu, Guo-Qing

Solution of difficult groundwater flow and transport problems is made easier when the groundwater equipotentials are coupled with streamlines. This approach, embedded in a new formulation of the Complex Variable Boundary Element Method (CVBEM), is shown to readily solve groundwater flow and transport problems. Examples of this method are presented for recalcitrant problems related to flow under a dam, dipole transport, and regional groundwater flow. The presented technique solves the two-dimensional Laplace equation using Ordinary Least Squares (CVBEMlOLS). This strategy is used to determine unknown boundary values at nodes along the exterior boundary. Once all boundaly values are known, the problem is reformulated in the complex potential plane to solve for the complex position of specified potential-streamline pairs so that the flownet can be constructed. This strategy greatly simplifies the determination of groundwater flownets, capture zones, solute-front migration, and travel times.
Predicting the Fate of Imidacloprid in a Coastal Plain Setting Using VS2DT

(Georgia Institute of Technology, 1997-03) Burkingstock, Bryan K. ; Bush, Parshall B. ; Berisford, Yvette C. ; Dowd, John F. ; Feild, James B. ; Johnson, West W. ; Rasmussen, Todd C. ; Taylor, John W.

Imidacloprid has been shown to control pine tip moths (Rhyacionia spp.) in loblolly pine seedlings (Pinus taeda L.). We describe an imidacloprid dissipation study on a small watershed near Downs, Georgia. Field data are utilized to calibrate the computer model VS2DT (Variably Saturated 2- Dimensional Transport) that uses a fmite-difference approximation of the advection-dispersion equation to simulate contaminant transport through variably saturated porous media. The site is simulated in a vertical cross section (X-Z plane) of a treated watershed from the soil surface to the water table (approximately 60 ft) spanning 260 ft horizontally. The cross section is centered on an ephemeral stream which drains the watershed, but for symmetry reasons, only half (130 ft horizontal distance) of the cross section is modeled. Modeling results show that imidacloprid moves more rapidly through sandy soils than sandy clay loam soil material. No imidacloprid concentrations above the detection limit of 0.6 ppb are predicted for the lysimeters in the unsaturated zone or in groundwater.
Recommendations of the Georgia Board of Regents' Scientific Panel on Evaluating the Erosion Measurement Standard Defined by the Georgia Erosion and Sedimentation Act

(Georgia Institute of Technology, 1995-04) Kundell, James E. ; Rasmussen, Todd C.

The 1993 Senate Stormwater Control Study Committee reviewed the Georgia Erosion and Sedimentation Act of 1975 and, among other recommendations, petitioned the Lieutenant Governor to request that a scientific panel be appointed by the Board of Regents to make recommendations for a turbidity instream standard necessary to protect state waters from siltation and sedimentation.' This review by a scientific panel was incorporated in the 1994 amendments to the Georgia Erosion and Sedimentation Act.' At the behest of the Lieutenant Governor, the Board of Regents submitted the names of qualified individuals to James E. Kundell of the Carl Vinson Institute of Government and requested that he convene the panel and coordinate its work? The panel met on five occasions between May and December 1994, to consider the issues before it and to develop recommendations for the Board of Natural Resources. The report of the panel was submitted to the Board of Natural Resources in January 1995.4 This paper presents the recommendations of the panel.
Hydraulic Evidence For Vertical Flow From Okefenokee Swamp To The Underlying Floridan Aquifer In Southeast Georgia

(Georgia Institute of Technology, 1995-04) Kitchens, Susannah ; Rasmussen, Todd C.

rapid response is observed between water level fluctuations in the Okefenokee Swamp and water levels in the underlying Floridan Aquifer. A lag of approximately one month is common, and a hydraulic diffusivity of 3.83 x 10-3 m2 s4 best matches the calculated aquifer response to the swamp water level perturbations. The magnitude of leakage between the swamp and the aquifer is uncertain because of a lack of knowledge about the specific storage coefficient in the aquitard separating the swamp and the aquifer which has not been explicitly measured. An intermediate value of specific storage within the likely range of values results in a downward vertical flow of 1.2 meters of water per year. This induced recharge can significantly alter the natural water balance within the swamp. Such a large loss of water from the swamp may be responsible for observed pH and water level changes, and increased heavy metal accumulations in aquatic organisms in the swamp.
Field vs. Laboratory Permeability Estimates

(Georgia Institute of Technology, 1993-04) Rasmussen, Todd C.

Estimates of subsurface fluid flow and solute transport parameters are used to model the migration of contaminants, as well as to predict the efficiency of proposed remediation strategies. Important parameters can be measured using laboratory analyses conducted on cores, or using field tests. To compare the representativeness of field vs. laboratory procedures, both laboratory and field estimates of hydraulic conductivity and air permeability were collected from an unsaturated fractured rock. Measured parameters were obtained from a large sample of 105 core segments collected at 3-m intervals. Field borehole tests were also conducted over 3-m intervals centered at the location where the core segments were collected.
The Role and Design of Water Quality Monitoring on Forested Watersheds

(Georgia Institute of Technology, 1993-04) Chen, Y. David ; Rasmussen, Todd C.

While many point sources of pollution have been ameliorated over the last twenty years, nonpoint sources (NPSs) of pollution remain a serious threat to the nation's water quality (Reilly, 1991). On a national scale, silvi-culture is one of the leading causes of NPS pollution, and has been identified as a localized problem in the Southeast (Myers, et al., 1985). Because forested watersheds often possess the nation's best quality waters, NPS control programs for protecting these waters must be undertaken. In this paper, a conceptual framework is established that shows the complex interrelationships between management mechanisms, investigation methods, and criteria and assessment methodologies for silvicultural NPS pollution control. The role and definition of water quality monitoring for the operation of this management framework is discussed, and the fundamental components related to the design of water quality monitoring programs are discussed. The monitoring programs include monitoring objectives, sampling stations and frequency, and environmental parameters. It should be emphasized that there does not currently exist a technical guide for forest water quality monitoring in the Southeast. It is the intent of this paper, therefore, to draw upon monitoring guidelines developed for other regions, and to clarify the role of water quality monitoring and to propose general design guidelines for implementing forest water quality monitoring programs in the Southeast.