Category: Research Sponsored by GWRI

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.

Principal Investigator: James Hook (University of Georgia)

Sponsor: GWRI
Start Date: 1990-04-01; Completion Date: 1991-03-31;
Keywords: None

Description:
Knowledge of water demands during periods of severe drought is needed to develop strategies for water management. Determination of amount and timing of water withdrawals is necessary for water managers to predict the impact of irrigation on groundwater reserves. As information becomes available on location of wells, aquifers tapped, acres irrigated, and crops managed, we will be able to anticipate water needs for irrigation. This will help in licensing new wells,anticipating seasonal drawdown, and recommending water use optimization. A first step in this examination is water use during drought years. The specific objectives of this proposal were 1) to determine the amount and schedule of agricultural demands for groundwater in years of severe droughts, and, 2) to estimate the impact of water restrictions on irrigation water use and water use efficiency.
The potential (no-water stress) and the lowest (no irrigation) yields for corn, soybean and peanut were calculated using three publicly available crop growth and water use models – CERES-Maize, SOYGRO, and PNUTGRO models, respectively. Rainfall, temperature, and solar radiation records were used with these models to identify the 15 most severe drought years in the 53 year record in the central Coastal Plain region of Georgia. Irrigation needed to bring yields into the range 80 to 90% of potential yields was determined for these drought years. Water use efficiency with and without irrigation was estimated. The amount and time of water withdrawals which could be expected for those severe drought years was calculated using the current cropping patterns and irrigated acreage in two multi-county regions in the Georgia Coastal Plain – the Dougherty Plain Region and the Georgia Cooperative Extension Southwest District.
Corn and soybean were more severely affected by drought than peanut. In the 15 driest years, yield losses for corn averaged 75% and, for soybean, 73%. For peanut, an average of 64% of the yield was lost due to drought. Of particular interest, almost half of the 15 worst drought years since 1938 occurred after 1979. The average irrigation needed to meet crop water needs was computed for 10-day periods. Most of the irrigation needs of corn in these drought years occur before irrigation is needed for peanut or soybean. Peanut and soybean needs coincide during late summer. The 36-county Southwest Georgia Extension District, contains almost 75% of Georgia’s irrigated land. In 1989 the reported irrigated land area for corn, peanut, and soybean in that region was 70,300,133,300 and 29,300 ha. The combined effect of irrigation timing and land area on water withdrawals was calculated. For most of the 130 days between late May and late September, withdrawals could exceed 3 million m3 per day, on the average, for these severe drought years. Peak water use occurred in late-July, when peanut irrigation was underway. Similar estimates were made for the Dougherty Plain area in Southwest Georgia. Further application of the techniques used here could lead to county or watershed specific estimates of maximum water needs.

Principal Investigator: Terry W. Sturm (Georgia Tech)
Principal Investigator: Ronald E. Kirby, Jr. (Georgia Institute of Technology)

Sponsor: GWRI
Start Date: 1990-04-01; Completion Date: 1991-03-31;
Keywords: Erosion, Sediment transport, Urban runoff, Settling basins, Design criteria, Urbanization

Description:
This research has focused on an evaluation of current design criteria and best-management practices for controlling sediment in runoff from construction sites in response to recent Georgia legislation which established an effluent limit on turbidity. The research approach has been two-pronged with an analysis of field data collected by Georgia EPD and of numerical data generated by a computer simulation model. The field data were collected at landfill sites which had a sediment basin. Regression relations between suspended solids in mg/l and turbidity in NTU were developed for each landfill site and were found to be dependent on the soil types at each site, which included clay loam, loam, and sandy loam. The field data indicated that the sediment basins at two of the landfill sites met the turbidity discharge standard for all storm events sampled while the sediment basin at a third site did not. It is apparent from the field data that the probability of meeting the turbidity discharge standard is dependent on rainfall characteristics, the hydrologic condition and size of the watershed contributing to the receiving stream, soil properties and soil conservation measures on the disturbed watershed, and the sediment basin design.

Computer simulation results were obtained from the model SEDCAD+ for disturbed watersheds with sediment basins designed according to the Georgia Erosion and Sediment Control Manual. The results showed that sediment basins can be very effective in reducing suspended sediment in construction-site runoff. However, for a disturbed area with significant soil-conservation treatment, the peak sediment concentration in the sediment-basin outflow exceeded the undisturbed peak concentration for a meadowland use. This was the case for storm recurrence intervals from 2 to 25 years and for all three soils tested. For an undisturbed land use of 1/3 agriculture, 1/3 woods, and 1/3 pasture, disturbed sediment concentrations in the sediment-basin outflow were less than the undisturbed values. Sediment-basin trap efficiencies obtained from the numerical model varied from approximately 45 percent for the clay loam soil to 80 percent for the sandy loam soil. The trap efficiencies decreased with increases in surface loading rate. The numerical results suggest that an improvement in the design criteria for sediment basins would be to re-define the surface loading rate and to specify lower allowable values for soils with high percentages of clay. The numerical results also quantitatively demonstrate the importance of applying soil conservation measures so as to prevent as much sediment as possible from ever reaching the sediment basin.

Principal Investigator: Ronald M. North (University of Georgia)
Principal Investigator: Jackie Sellers (University of Georgia)

Sponsor: GWRI
Start Date: 1989-04-01; Completion Date: 1990-04-01;
Keywords: water demand, forecasting, water use, demand models, water pricing, conservation.

Description:
Direct water demand estimates are useful for resolving capacity needs, system expansion, financing of systems, acquiring and issuing water use permits from water authorities and for efficient management purposes. Hickman and Associates, Inc. developed a water use forecasting system called MAIN (Municipal and Industrial Needs system). This was later adopted by the Institute for Water Resources, Corps of Engineers, our source for the program to calibrate for Georgia conditions.

Our experiences with calibrating the IWR-MAIN model were not as accurate as some of the reported calibration tests in western states. Our best reconciliation of IWR-MAIN estimate for 1990 (23.6 mgd) with data supplied by the Macon/Bibb County Water Authority (21. 8 mgd) was 7.5% higher than the water authority records, excluding public and unaccounted uses. The USGS estimated uses for publicly supplied water at 28.3 mgd was 7.6% higher than the IWR-MAIN estimate of 26.3 mgd and 15% higher than the estimate from the Macon/Bibb County Water Authority. Implementation of two conservation programs in Macon indicate water savings for out years (1990-2010) could be reduced by four to seven percent. We conclude that the IWR-MAIN water demand forecasting system would provide reasonably consistent results because of the standard methodology used if it were applied throughout the state of Georgia.