Category: Research Sponsored by GWRI

Sponsor: GWRI
Start Date: 1992-04-01; Completion Date: 1992-04-01;
Keywords: Reservoir Operation, Electric Power, Water Supply, Competing Uses, River Forecasting

Description:
A major complicating factor in water resources systems management is handling unknown inputs. Stochastic optimization provides a sound mathematical framework but requires that enough data exist to develop statistical input representations. In cases where data records are insufficient (e.g., extreme events) or atypical of future input realizations, stochastic methods are inadequate. This article presents a control approach where input variables are only expected to belong in certain sets. The objective is to determine sets of admissible control actions guaranteeing that the system will remain within desirable bounds. This approach is applied to the operation of Lake Lanier, a U.S. Army Corps of Engineers multiobjective reservoir and is shown to be an effective management tool. This investigation led to the following conclusions: (1) Increases of dependable energy generation are possible, albeit at the expense of wider reservoir level fluctuations and more frequent water shortages. Thus, recreation and water supply reliability are in conflict with energy generation. (2) Good quality forecasts can minimize lake level fluctuations and, at the same time, meet higher dependable energy commitments and water supply requirements. (3) Forecasting also facilitates reservoir operation with maximum outflow and generation hour restrictions. Such constraints can be used to minimize off-peak energy generation, thus maximizing overall energy value.

Technical Report

Principal Investigator: Aris Georgakakos (GWRI/Georgia Tech)
Principal Investigator: Huaming Yao (GWRI/Georgia Tech)

Principal Investigator: Seth Rose (Georgia State University)

Sponsor: GWRI
Start Date: 1993-08-01; Completion Date: 1993-08-01;
Keywords: Environmental Tritium, Stable Oxygen Isotope Ratios,Ground Water, Surface Water, Well-Pumping

Description:

Systematic temporal isotopic (δ180 and 3H) and geochemical variation was analyzed within precipitation, shallow ground water, baseflow and deeper ground water from the southeastern Piedmont Province of Georgia. These samples, acquired predominantly during 1992, provide a valuable addition to a growing set of environmental isotopic data for this region. There was a substantial degree of isotopic variation (mostly random) observed between successive precipitation events; however,only a relatively small degree of variation observed within shallow ground water, baseflow and deeper ground water acquired from four production wells. Typically δ180 and 3H values varied by ~5% within ground water between successive 1.5 – 3.0 month sampling periods. Stable oxygen isotope ratios within deeper ground water (derived from production wells) systematically decreased by ~0.5 to 1.0 per mil during the summer months. However, accompanying trends were not observed with respect to either tritium or major ion concentrations. There is little to infer from these data that ground-water pumping rates appreciably affects the age distribution (generally 15-35 years) of ground water within these small Piedmont basins. Ground water becomes isotopically well homogenized (however, not perfectly homogenized) as the result of dispersion and the exchange of water upon clay mineral surfaces.

Principal Investigator: David Wenner (University of Georgia)

Sponsor: GWRI
Start Date: 1993-04-01; Completion Date: 1993-04-01;
Keywords: oxygen isotopes, groundwaters, confined aquifer,unconfined aquifer, phreatic aquifer

Description:

A total of 127 groundwater samples were analyzed to date for their oxygen isotopic composition from 50 counties throughout the Coastal Plain of Georgia during the period from June 24, 1992 to September 17, 1992. Samples from shallow wells (<200 ft.) have measurable north to south isotopic variations, coincident with yearly mean rainfall. In general, groundwaters from the Upper Coastal Plain are about 1‰ more negative than those from the Lower Coastal Plain. Groundwaters from varying depths also have differing δ180 values, although inland and coastal areas appear to have contrasting isotopic patterns. For example, samples from cluster wells varying from 180 feet to >1200 feet deep from coastal Glynn County show oxygen isotopic enrichment with increasing depth, probably due to sea water encroachment. In contrast, samples from wells ranging from 35 feet to 900 feet deep from Worth County in south central Georgia do not have isotopic variations that correlate with depth. At both sites, however, groundwaters taken from different hydrostratigraphic levels have small isotopic variations (0.6 ‰). The present stable isotopic data set is not sufficient to be able to quantify the amount of leakage between aquifers at different hydrostratigraphic zones within the Coastal Plain.

Principal Investigator: Jeffrey L. Jordan (University of Georgia)

Sponsor: GWRI
Start Date: 1993-03-01; Completion Date: 1993-03-01;
Keywords: Economics, Water Demand, Planning

Description:

This report used the contingent valuation method to estimate the willingness-to-pay (WTP) for water as a commodity. Analysis was based on a telephone survey of Georgia residents conducted in 1992. Results indicated that the average WTP was about nine dollars per month above current monthly water cost. This research, funded through the Georgia Water Research Institute Program, benefited from the work of Abdelmoneim H. Elnagheeb, Post-Doctoral Research Associate, Department of Agricultural and Applied Economics, Georgia Experiment Station, University of Georgia, Griffin, GA 30223-1797.

Principal Investigator: Evangelos A. Voudrias (Georgia Institute of Technology)
Principal Investigator: J. M. Wampler (Georgia Institute of Technology)
Principal Investigator: Charles E. Weaver (Georgia Institute of Technology)

Sponsor: GWRI
Start Date: 1992-04-01; Completion Date: 1993-03-31;
Keywords: Organoclays, Quaternary ammonium ions, Clay minerals, Montmorillonite, Sorption, Adsorption and exchange, Aromatic hydrocarbons, Organic wastes, Wastewater treatment

Description:

The sorption at room temperature of benzene and naphthalene from water and from methanolwater mixtures by four different organophilic clays has been determined. The organophilic clays were prepared from Wyoming montmorillonite by replacing the natural exchange ions of the clay by the quaternary ammonium ions TMA (tetramethylammonium), TMPA (trimethylphenylammonium), HDTMA (hexadecyltrimethylammonium), and BDTDA (benzyldimethyltetradecylammonium). Of these organoclays, TMPA-montmorillonite has the greatest sorptive ability for naphthalene and is followed in order of decreasing sorptive ability by BDTDA-, HDTMA-, and TMA-montmorillonite. TMA-montmorillonite is much more effective as a sorbent for benzene than it is for naphthalene. For benzene sorption, TMPA-montmorillonite is most effective, followed in order by TMA- and BDTDA-montmorillonite. The presence of methanol as a co solvent reduces the sorption coefficients in the manner predicted by the solvophobic theory of Rao et al. (1985), that is, the sorption coefficients decrease approximately in log-linear fashion as the methanol content increases, but the decrease in the sorption coefficients is generally less than that to be expected because of increasing solubility of the sorbate with increasing methanol content (that is, the value of a is less than 1). As others have shown, the form of the isotherms for sorption of benzene and naphthalene from water by organoclays having small quaternary ammonium ions (TMA and TMP A) indicates that adsorption is the primary mechanism of sorption. Organoclays having a long-chain alkyl substituent on the organic cation (BDTDA- and HDTMA-montmorillonite) sorb by a mechanism that is essentially partitioning of the sorbate between water and the organic material in the clay interlayers. The cosolvent methanol affects the form of the isotherms, causing the isotherms to become progressively closer to linear form as the fraction of methanol in the liquid phase increases. This observation is interpreted to indicate that the partitioning mechanism of sorption becomes predominant as the methanol content of the solvent increases. Isotherms obtained from single-step desorption experiments indicate that sorbed naphthalene reaches equilibrium with fresh methanol-rich solvent in less than 48 hours, but if the volume fraction of methanol is 30% or less, such equilibrium may not be achieved in 48 hours.

Principal Investigator: Terry Snell (Georgia Institute of Technology)
Principal Investigator: Nancy Walls (Georgia Institute of Technology)
Principal Investigator: David Dusenbery (Georgia Institute of Technology)
Principal Investigator: Lloyd Dunn (Georgia Institute of Technology)

Sponsor: GWRI
Start Date: 1992-04-01; Completion Date: 1993-04-01;
Keywords: sediment toxicity, biomarkers, rapid toxicity assessment, enzyme inhibition, ingestion rate, fluorescence

Description:
Sediment samples were collected from 23 sites in Utoy Creek and its tributaries over a distance of about 12 km. Toxicity tests were performed on sediment elutriates using the freshwater rotifer Brachionus calyciflorus and the nematode Caenorabditis elegans. Several endpoints were evaluated in the rotifer tests including mortality, swimming activity, enzyme activity and ingestion rate. For nematodes, LC50s were estimated using mortality as endpoint. Toxicity was detected at several sites in an industrial area near two former wood treatment plants. 80% of the stations sampled in a small tributary draining this site contained sediments with significant toxicity. Some sediment elutriates were quite toxic, requiring 97% dilution to remove toxic effects. A toxicity identification evaluation was performed on elutriates from station 6. About 50% of the toxicity was removed by passage over a XAD-2 or activated charcoal column, both of which remove organics. Passage of elutriate over an Amberlite-200 column that removes cations eliminated virtually all of the toxicity. Addition of 50 μm EDTA likewise removed most of the toxicity. Analysis of extracts from the XAD-2 column with GC-mass spectroscopy revealed the presence of several non-polar organic compounds including derivatives of pentanone, benzene, dimethylstyrene, napthalene, and cyclohexane. In addition to the sediment samples, the toxicity of 10 pure chemicals was investigated using rotifer esterase and PLA2 inhibition and ingestion rate tests to develop a data base for comparison to other species. Ingestion rate NOEC was consistently more sensitive than LC50s by a factor of 3-35, depending on the chemical. Reproductive rate NOEC was usually more sensitive than ingestion rate NOEC by a factor of 2-10 times. The relative sensitivity of esterase and PLA2 enzyme inhibition compared to ingestion rate varied with each chemical. Relative sensitivity could not be predicted a priori for broad classes of toxicants like metals, organics and pesticides. Ceriodaphnia and B. calyciflorus had identical LC50s for station 6 elutriate, however, rotifer ingestion rate NOEC was 12 times lower. The LC50 of nematodes exposed to whole sediments was a less sensitive measure of toxicity than rotifer ingestion or enzyme inhibition tests. Use of the rapid toxicity tests described here could 

Principal Investigator: Mary C. Mayhew (Gainesville College)
Principal Investigator: Edmond A. Mayhew (Gainesville College)

Sponsor: GWRI
Start Date: 1991-04-01; Completion Date: 1992-03-01;
Keywords: water quality, phosphorus, chlorophyll, transparency, sedimentation, clay, trophic state

Description:

There is evidence that southeastern reservoirs have lower than expected concentrations of phosphorus and algae due to coprecipitation with clays. This appears to be true for Lake Lanier, a major reservoir in N.E. Georgia. The purpose or this study was to investigate the effects of clay on phosphorus and algae and to determine the impact of these effects on Carlson’s Trophic State Index. Clays from the watershed were collected and measured for their phosphorus content and adsorption of phosphorus, which was similar to that for kaolin. Suspensions of clay were added to cultures of the blue-green alga Chroococcus limneticus grown in Bold’s medium and in Rhodes’ medium. Little coprecipitation of algae and phosphorus occurred in the more concentrated Bold’s medium; the more dilute Rhodes’ medium showed precipitation of algae and phosphorus with clay additions. Sediment traps in a tributary of Lake Lanier had high rates of sedimentation of organics and phosphorus, although there did not appear to be a direct coupling between clay and algal sedimentation, as some previous studies indicated. Field sampling of the lake showed deposition of algae, phosphorus, inorganics (clay), and organic matter from upstream to open lake stations. The result indicates that clays do have a profound effect upon Lake Lanier and that the Trophic State Indices for chlorophyll and phosphorus are low due to clay coprecipitation. The TSI for transparency is influenced by inorganic turbidity but is nonetheless the best indicator of the trophic status of the lake eutrophy. An important finding of this study is that siltation is reducing the phosphorus and algae in the water column, and thus slowing the effects of eutrophication. If silt loading is controlled without controlling phosphorus loading, the lake will show algal blooms and other characteristics of eutrophy.

Principal Investigator: Terry W. Sturm (Georgia Tech)

Sponsor: GWRI
Start Date: 1991-04-01; Completion Date: 1992-03-31;
Keywords: Erosion, Sediment transport, Urban runoff, Settling basins, Design criteria, Urbanization

Description:
This research has focused on an evaluation of current design criteria for meeting an effluent turbidity limit in runoff from construction sites and landfills in Georgia. The research has been completed in two-phases. In Phase I, field data collected by Georgia EPD were analyzed, and the effectiveness of sediment basins in reducing turbidity was studied using numerical data generated by a computer simulation model. In Phase II, the numerical model was used to investigate the effect of changing various sediment basin design criteria, and a new sediment basin design procedure was developed. Both the field data and the numerical simulation results from Phase I showed that sediment basins can be very effective in reducing suspended sediment in runoff, but they cannot meet the turbidity standard in all cases without additional erosion control measures. In Phase II of the research, it was found that the major factor affecting sediment basin performance is soil type followed by basin surface area. The value of erosion control measures used in combination with sediment basins was demonstrated. The proposed design criteria include a detention storage based on the runoff volume from frequent storms; a minimum sediment basin surface area which is a function of soil grain size; a minimum level of erosion control; and a comparison of peak outflow sediment and water discharges with those from the undisturbed watershed. This approach provides a uniform and rational design basis for optimizing sediment basin design to meet the turbidity standard.

Principal Investigator: George Vellidis (University of Georgia)
Principal Investigator: Matt C. Smith (University of Georgia)
Principal Investigator: Richard Lowrance (University of Georgia)
Principal Investigator: Robert K. Hubbard (Southeast Watershed Research Laboratory)
Principal Investigator: Joseph C. Johnson, Jr. (University of Georgia)
Principal Investigator: Larry Newton (University of Georgia)

Sponsor: GWRI
Start Date: 1991-04-01; Completion Date: 1992-03-31;
Keywords: wetlands, restoration, bioremediation, nutrients, ground water, surface runoff, nitrogen, phosphorus

Description:
The feasibility and effectiveness of restoring a riparian wetland and using it as a bioremediation site for nutrients moving downslope from an animal waste application site is being evaluated. In question is the short-term effectiveness of the restored wetland in enhancing the quality of the water leaving the site. Details on wetland restoration and instrumentation used for measurement of nutrient movement through the wetland in surface runoff and shallow groundwater are presented. The data from the first year of restoration are inconclusive and indicate that the vegetation which was used to restore the wetland is too recently established to significantly affect nutrient assimilation and retention in the wetland. The study is being continued for an additional 2-year period at the end of which the effectiveness of the restored wetland will be reevaluated. The instrumentation, the sampling schedule, and the techniques that are described are well suited to evaluate the bioremediation potential of a restored wetland.

Principal Investigator: Lynn J. Torak (Hydrologist -U.S. Geological Survey)
Principal Investigator: Shahrokh Rouhani Ph.D (Newfields Inc)

Sponsor: GWRI
Start Date: 1991-06-01; Completion Date: 1991-06-01;
Keywords: Ground-water, Hydrogeology, Statistical Methods, Regional Analysis

Description:

The parameter estimation is a crucial phase of any ground water flow investigation, which determines the success or failure of the prediction process. The commonly used parameter-estimation approaches are based on various inverse procedures that in many instances prove to be inadequate. This report presents an advanced alternative approach which is based on the geostatistical co-estimation technique, known as co-kriging. The investigated parameters are: aqulfer transmissivity, piezometric head, and residual, which is defined as the computed minus the measured water level at a specified location. Values of computed head were obtained by using the MODular linite ~lement model (MODFE) of two-dimensional ground water flow. The data set was derived from a regional study of the Upper Floridan aquifer in southern Georgia. The initial results indicate that the log-transformed transmissivity and the uncalibrated residual are suitable for co-estimation. Direct kriging provides estimated maps for these variables, which are unbiased linear estimates with minimum variance of estimation. The co-kriging goes one step further by permitting the incorporation of measured values of both parameters in the estimation processes of each one. The results indicate that the co-kriged maps represent more spatial details with higher accuracy than their ordinary kriged counterparts. Considering the high cost of field tests in ground water investigations, the above more efficient co-estimation process offers an attractive alternative for parameter evaluation than previously used inverse procedures.