Category: Research Sponsored by GWRI

Principal Investigator: Elizabeth Blood (Albany State University)

Sponsor: GWRI
Start Date: 2002-03-01; Completion Date: 2003-02-28;
Keywords: Management and Planning

Problem Statement:

The Flint River Basin is in the cross-hairs of public policy debate on water. Atlanta resides in the headwaters, irrigated agriculture in the lower basin, and the entire basin is a critical component of the Alabama, Georgia, and Florida interstate water compact negotiations. Concerns over unsustainable consumption of water resulting from uncontrolled growth of metro-Atlanta; water quality issues associated with this urbanization; and agricultural withdrawals of groundwater in southwest Georgia have made water the focus of public policy debate. Conflicts are arising over these water withdrawals to fuel growth, the economy, and sustain the natural resources. During the past four years, these concerns have been heightened by the most severe and prolonged drought of record. This drought has resulted in record low flows and water levels in reservoirs and aquifers; water restrictions and bans; domestic and municipal well failures; communities with fewer than two weeks municipal reserves, and negative impacts on natural resources have raised concerns over long-term water security.

An effective water management strategy is clearly needed to address these challenges and provide a fair and equitable process to allocate and sustain the water resources. The North Georgia Metropolitan Planning District was the first regional strategy created to address the water resource issues. The plan encompasses sixteen counties forming the Greater Atlanta metropolitan area including the upper basin of the Flint River. The Flint River Basin has distinct regional differences in water issues, concerns, and values; sociology; economy; natural resources; governance; and management infrastructure. The formal structure and organization of the metro plan will not work for rural Georgia or the lower Flint River basin. Water decisions, management, regulation and infrastructure are controlled by county, municipal, or organizational entities in the upper basin. In the lower basin, water decisions, management, and infrastructure are primarily controlled by individuals. County and municipal oversight is restricted to a few larger cities. The water management plan; the planning process and organizational structure; and the implementation options, infrastructure, and policy must be developed to incorporate regional perspectives, values, opportunities, and resources.

Principal Investigator: Ching-Hua Huang (Georgia Tech)

Sponsor: GWRI
Start Date: 2002-03-01; Completion Date: 2003-02-28;
Keywords: Water Quality, Water Treatment, Wastewater

Description:

Results of this study indicate that representative members of three environmentally relevant antibiotic classes – fluoroquinolones, sulfonamides, and dihydrofolate reductase (DHFR) inhibitors – are substantially degraded under conditions simulating chlorination of water supplies during disinfection processes, yielding a wide variety of lower and higher mass degradates. The mechanistic understanding of the reactions between chlorine and these three antibiotics classes provides a critical basis for predicting the fate of related antibiotics and pollutants in the chlorination disinfection processes.

Principal Investigator: Bruce Beck (University of Georgia)

Sponsor: GWRI
Start Date: 2001-03-01; Completion Date: 2002-02-28;
Keywords: Surface Water, Iron, Nutrient Dynamics, Phosphorus

Introduction:

The complex interactions iron and phosphorus play a primary role in the availability of phosphorus in surface waters of the Georgia Piedmont. Exploration of these dynamics can provide information for nutrient management in surface water systems of this region. The soils of the Georgia Piedmont are rich in iron primarily as iron hydroxides (oxidized iron). Iron hydroxides form a ligand exchange with phosphate ions, making the phosphate biologically unavailable. Phosphorus, particularly inorganic phosphate, delivered through non-point source runoff to receiving waterbodies may be sorbed to iron hydroxides and not biologically available, while phosphorus, as organic phosphorus, delivered from a point source (such as an effluent pipe) may be immediately biologically available. Illuminating the biogeochemistry of phosphorus in surface waters rich in iron hydroxides will provide information useful in setting local water quality criteria and standards, and will help define the relationship between point and non-point pollution in surface waters receiving runoff from iron-rich soils.

The paradigm for phosphorus cycling was developed based on data from lakes in northern temperate regions. Lakes in north temperate regions tend to be glacial in origin. The phosphorus cycling paradigm in north temperate systems involves the sinking of inorganic particulates and organic material which result in a steady increase in dissolved phosphorus in the hypolimnetic waters of strongly stratified lakes. The dissolved phosphorus is then recirculated to the lake at fall mixis (Hutchinson 1957; Wetzel 1983; Goldman and Horne 1994). In contrast, Southeastern Piedmont lakes are primarily man-made impoundments. The climate in the southeastern US provides for a longer growing season and warmer annual average temperatures than those found in north temperate regions. This difference in climate affects the strength and length of summer stratification, and creates the conditions for monomictic rather than dimictic lakes in the southeastern Piedmont. The parent geology of the southeastern Piedmont is responsible for the differences in the cycling of phosphorus in southeastern Piedmont systems. The high iron content of the soils in the southeastern Piedmont provides transport of iron via runoff to aquatic systems in this region. The steady increase in hypolimnetic P during stratification, and the pulse of soluble P at fall turnover, is not found in southeastern Piedmont lakes. Oxidized iron in the water column binds phosphate via surface sorption and ligand exchange. We hypothesize that this sorption removes inorganic phosphorus from the biologically available fraction, thus creating a different lake phosphorus cycling regime for systems in the southeastern Piedmont.

We investigated the biogeochemical processes involved in the cycling of phosphorus as phosphate in the iron-rich waterbodies of the Georgia Piedmont. We explored the sorption chemistry of iron and phosphorus using the chemical equilibrium model MINTEQ. We conducted laboratory studies of the geochemical processes involved in phosphorus and iron interactions in surface water. We also conducted corresponding fieldwork on Lake Lanier sampling metals and phosphorus at depth four times in the annual cycle, to investigate the current roles of iron and phosphorus in the surface waters of Lake Lanier. The work conducted in this study will allow us to help identify appropriate in waterbody concentrations of phosphorus, given the local geochemistry, for local waterbody specific water quality criteria and standards, and may help evaluate appropriate parameters for monitoring significant changes in water quality of Lake Lanier.

The MINTEQ model program was released initially by USEPA in 1991 as a chemical equilibrium model for the calculation of dilute aqueous solutions in the laboratory or in natural aqueous systems. The model can calculate the equilibrium mass distribution among dissolved species, adsorbed species, and multiple solid phases under a variety of conditions and gas phase partial pressures. MINTEQ comes complete with a comprehensive database, and also allows for user defined parameter input [http://www.epa.gov/ceampubl/minteq.htm]. We used the VMINTEQ model program, which is a modified form of the MINTEQ model to explore the iron-phosphorus chemistry of Georgia Piedmont lake systems. VMINTEQ has been modified by the addition of a Visual Basic interface and the Stockholm Humic Model sub-model to include dissolved organic matter interactions using the diffuse layer model rather than the Gaussian distribution for organic matter physical chemistry (Gustaffson 2001). The laboratory experiments we conducted utilized the results of the model runs to determine initial conditions for the sorption capacity experiments.

The laboratory experiments were conducted in multiple phases. The first phase involved 24 and 48 hour sorption capacity experiments. The second phase involved measuring changes in sorption of phosphorus to iron in the presence of elevated organic matter introduced as concentrated humate in the form of Agrolig powder. The final phase of the planned laboratory work involving algal response to additions of iron complexed phosphorus was not completed due to time and funding constraints.

The third component of our work included depth measurements of metals, nutrients, and basic water chemistry parameters taken four times in the annual cycle on Lake Lanier. We analyzed these data to evaluate the hypothesis that phosphorus cycling in Georgia Piedmont lakes differs significantly from the northeast temperate lake paradigm. Measurements at depth of iron, manganese, and phosphorus show the lack of phosphate in the anoxic bottom waters, and the lack of soluble iron at the sediment-water interface. These measurements help define the role of iron in the phosphorus cycle in Georgia Piedmont lakes.

Principal Investigator: Aris Georgakakos (GWRI/Georgia Tech)

Sponsor: GWRI
Start Date: 2000-04-15; Completion Date: 2002-02-14;
Keywords: Flow requirements, In-stream Biological Integrity, Trade-off Analysis, Interbasin Transfer

Scope of Study:

The purpose of this study is to assess the response of the ACF river basin to biological integrity requirements. These requirements are quantified in a preliminary guidance document drafted by US EPA and the Fish and Wildlife Service (1999).

Principal Investigator: Aris Georgakakos (GWRI/Georgia Tech)

Sponsor: GWRI
Start Date: 2001-03-01; Completion Date: 2002-02-28;
Keywords: Basinwide planning, Decision support systems, Irrigation assessment, Technical

Abstract:

The water resources systems of the Southeastern U.S. are increasingly stressed by various demands. This stress is magnified during the periodic periods of drought that occur in the region, and agriculture is particularly affected by these droughts. Recent public policy has attempted to mitigate the impacts on farmers, but reliable methods of drought assessment and forecasting are needed to allow efficient policy implementation. A methodology is presented to assess the effects of droughts on crop yields, irrigation demands, and the full yield- irrigation relationship. The technique utilizes irrigation optimization algorithms coupled with physiologically based crop models. Ensembles of climatic forcing allow for quantification of the stochastic crop-water production function at specific sites and quantification of the changes in this function in drought periods. Data needs for assessment are discussed as well as sensitivity of the methodology to some input parameters. The technique is applied to four case study sites in southwestern Georgia, and potentially useful information is derived. Options for drought forecasting are briefly discussed.

Principal Investigator: Aris Georgakakos (GWRI/Georgia Tech)

Sponsor: GWRI
Start Date: 1999-07-01; Completion Date: 2001-06-30;
Keywords: Surface aquifer linkages, Irrigation supply, Hydrologic budget

Project Description:

In the coastal area of Georgia, ponds are sometimes excavated at golf courses, farms, or communities by digging through sandy surface soils until the water table is reached. These man-made seepage ponds are often used to supply water for irrigation, and are thus a potential supplemental source of water to the Upper Floridan aquifer. Because the potential availability of water from seepage ponds is poorly understood in coastal regions, a test site will be selected for detailed evaluation.

This course will review the fundamentals of turbulence modeling for flows of engineering interest, discuss the latest advancements in model development and applications, and address a number of issues that are critical for successful numerical simulations of turbulent flows. The main emphasis will be on closure models for the Reynolds-averaged Navier-Stokes equations, as they provide the only practical framework for modeling complex flows. Isotropic eddy-viscosity models, non-linear eddy-viscosity models and algebraic and transport Reynolds-stress models will be presented and their relative performance in a number of complex benchmark flows will be discussed. Special emphasis will be placed on approaches for modeling the structure of turbulence near smooth and rough walls and free-surfaces as well as on turbulence models for sediment-laden and stratified flows. Numerical issues regarding the robust and efficient implementation of turbulence models in CFD flow solvers will also be emphasized.

Principal Investigator: Fotis Sotiropoulos (Georgia Tech)

Sponsor: GWRI
Start Date: 2000-03-01; Completion Date: 2001-02-28;
Keywords: Hydrodynamic Models, Open Channel Flow, Numeric Simulation

Summary:

In this report, we develop a two-dimensional hydrodynamic model for simulating swallow-water open-channel flows using depth-averaged equations. The model is capable of handling arbitrarily shaped channel geometries such as those typically encountered in natural rivers. The time-dependent, depth-averaged equations are formulated in generalized, non-orthogonal curvilinear coordinates so that complex river reaches can be accurately modeled using body-fitted computational grids. The equations are discretized in space using a conservative second-order accurate finite-volume method. Adaptive artificial dissipation terms, with scalar and matrix-valued scaling, are explicitly introduced into the discrete equations to ensure that the resulting scheme is applicable to all flow regimes and can accurately capture hydraulic jumps. The discrete equations are integrated in time using a four-stage Runge-Kutta method. For steady-state computations the convergence of the Runge-Kutta algorithm is enhanced using local time stepping, implicit residual smoothing, and multigrid acceleration. Time accurate solutions may also be obtained by integrating the governing equations in time using the four-stage, second-order accurate in time, Runge-Kutta scheme without implementing the aforementioned convergence acceleration measures.
To validate the numerical model, we carry out calculations for a variety of open channel flows for which experimental data have been reported in the literature. The calculated test cases include flow in strongly curved channels and channel expansions. For all cases considered the numerical method is shown to yield solutions of comparable accuracy to those reported in earlier studies in the literature using depth-averaged equations. Discrepancies between predictions and experiments are observed only for very strongly curved channels for which three-dimensional effects dominate.
Due to the lack of detailed bathymetry and flow measurement data for the ACT and ACF basins, the present numerical model was not applied to a real-life reach as was initially intended. This not withstanding, however, the method has been designed to be sufficiently general and its application to a natural geometry is straightforward. The good overall agreement between measurements and numerical simulations for the test cases considered in this report suggests that the present method could serve as a powerful computational tool for understanding the complex flow patterns in the ACT and ACF basins and for guiding the development of simpler one-dimensional models.

Principal Investigator: Peter Hartel (University of Georgia)

Sponsor: GWRI
Start Date: 2000-03-01; Completion Date: 2001-02-28;
Keywords: Coliform isolation, Pollution source assessment, Pollution transport assessment, Pollutant source control

Problem and research objective:

Fecal coliforms consist of several bacterial genera from the family Enterobacteriaceae that can grow on a selective medium at 44.5°C for 24 hours. Fecal coliforms normally inhabit the intestinal tract of warm-blooded animals and their presence in soil or water is a good indicator that the soil or water was contaminated by bacterial pathogens. For example, when numbers of fecal coliforms exceed 2,000 per 100 mL of water, the likelihood of bacterial pathogens in the water is 98.1% (Geldreich, 1970). Fecal coliform counts are typically used to monitor Georgia’s recreational waters.

One of the most vexing problems in isolating fecal coliforms from water samples is not knowing the host origin of these bacteria. In the past, the only way to identify the host origin of a bacterium was to observe the bacterium’s various phenotypic markers (i.e., characteristics expressed by the bacterium, like antibiotic resistance). The main problems with using phenotypic markers are their lack of reproducibility and lack of discriminatory power (ability to distinguish two closely related strains). However, in recent years, it has become possible to identify the host origin of a bacterium based on its DNA. This alternative method, called genotyping, not only has increased reproducibility, but also has increased discriminatory power. The most common of these genotypic methods include chromosomal DNA restriction analysis, plasmid typing, pulsed field gel electrophoresis, various polymerase chain reaction (PCR) methods, and ribotyping (Farber, 1996).

Each genotypic method has its advantages and disadvantages with respect to strains that can be typed, reproducibility, discriminatory power, ease of interpretation, and ease of performance. In this report, the genotypic method selected was ribotyping. Ribotyping is based on ribosomal RNA (rRNA). Ribosomal RNA is present in all bacteria, and is composed of three species, 5S, 16S, and 23S. The DNA in the bacterium that encodes for these three species of rRNA is usually present in 2 to 11 copies and is highly conserved (does not mutate; Grimont and Grimont, 1986). In ribotyping, the DNA is isolated from the bacterium and cut with a special enzyme that only recognizes certain DNA sequences (i.e., a restriction enzyme). The DNA is electrophoresed in a gel and the DNA transferred to a nylon membrane (this is called Southern blotting). The membrane is probed with a chemiluminescent copy of the 5S, 16S, and 23S portions of the DNA and, when properly treated, the membrane gives a pattern that can be scanned with an imager. As a method for distinguishing a subspecies of a bacterium, ribotyping is considered to have excellent reproducibility, good discriminatory power, excellent ease of interpretation, and good ease of performance (Farber, 1996).

Here, the fecal coliform selected for ribotyping was Escherichia coli. This bacterium was selected for five reasons. First, as a fecal coliform, E. coli is accepted by the American Public Health Association as a good indicator of pathogenic bacteria (Clesceri et al., 1998). Second, most environmental ribotyping has been done with this bacterium. As a result, the methodology for ribotyping this bacterium is established. Third, there is good scientific evidence that specific strains of E. coli are associated with different host species (e.g., Amor et al., 2000). Fourth, E. coli does not exist as a stable population in the environment unless the source of contamination is persistent. Fifth, E. coli is easy to isolate and easy to manipulate genetically.

Principal Investigator: Carolyn Ruppel (Georgia Tech)

Sponsor: GWRI
Start Date: 1998-09-01; Completion Date: 2000-08-31;
Keywords: Groundwater, Hydrogeochemistry, Water Quality

Problem and Research Objectives:

Three undeveloped barrier islands in coastal Georgia have been mentioned as possible sites for future developments. This has led to interests by regional planners in the impact of urbanization and ecosystem destruction on the hydrologic systems beneath these barrier islands. In fact, the availability and quality of fresh water resources on barrier islands are considered key factors controlling the sustainability of natural systems and human development, as well as the continued viability of ecosystems in adjacent wetlands. The goal of this project is to develop a baseline for monitoring future development related changes in surficial acquifer systems on the concerned islands. The project is scheduled to last two years, of which the first one has now been completed. The following text presents the preliminary results of year 1. It also provides an overview of the planned work for year 2.