Category: Research Sponsored by GWRI

Principal Investigator: John F. Dowd (University of Georgia)
Principal Investigator: Phillip J. Smith (University of Georgia)

Description:
The objective of this research is to evaluate field methods for estimating streamflow reductions due to pumping from nearby wells. This project is a supplement to previous work which provided a microcomputer model for estimating streamflow depletion due to pumping from nearby wells. Four direct measurement techniques and one indirect estimation technique are described and evaluated for estimating induced recharge through stream bottoms for phreatic and confined aquifers. Direct techniques are seepometers, minipieozmeters, temperature probes, and tracers. The indirect estimate is derived from streamflow correlations. Streamflow correlation estimates and tracers are not generally useful. Seepometers, minipiezometers, and temperature probes are useful for both phreatic and confined aquifers subject to certain bottom sediment and flow volume constraints.

Seepometers, minipiezometers, and temperature probes can be used to measure groundwater discharge from phreatic aquifers through fine-grained and relatively porous bottom sediments such as silts and sands. All three methods require clusters of at least five identical instruments to be installed at each of several measurement points in the stream bottom to properly assess micro- and meso-scale variability in sediment composition and groundwater flux patterns. Seepometers are the easiest to use and directly measure vertical flux through the stream bottom. Minipiezometers require accurate measurements of sediment saturated vertical hydraulic conductivity over the depth sampled, and temperature probes require the measurement of sediment specific heat and specific density and the thermal conductivity of the sediment-fluid complex. None of these three methods can be used in dense clay bottom sediments.

Seepometers and minipiezometers are inappropriate for estimating impacted discharge from confined aquifers. Springs are useful in assessing changes in discharge from confined aquifers. If local conditions do not allow installation of a V -notch wier or other precise instrumentation to directly measure spring discharge, then temperature probes can be used if the discharge volume and temperature gradient are sufficient to change the ambient stream temperature passing the spring during lowflow conditions. Temperature probes are easy to fabricate, install, and automatically monitor

Principal Investigator: Gian S. Ghuman (Savannah State College)
Principal Investigator: Kamalakar B. Raut (Savannah State College)

Sponsor: GWRI
Start Date: 1988-06-01; Completion Date: 1989-07-01;
Keywords: ion exchange, soil erosion, solute transport, toxic substances.

Description:

During 1988-89, release of major and toxic (trace) metals from two soil types in coastal Georgia was studied regarding the impact of rainfall. Results were compared in the runoff water from plots under grass and forest vegetation. Leaching experiments were conducted to evaluate the effect of two leaching solutions on the downward transport of metals. Runoff water samples were collected from four field plots (4m x 4m) into plastic buckets via a spillway laid-out in the corner of each plot. Four periodic collections of samples of runoff water were made after significant rainfall events from August to September, 1988. Water samples were filtered through 0.45 mMillipore filters and their pH was adjusted to 2.0 for the estimation of metals by atomic absorption spectroscopy. Six sequential leachings were conducted in 40 cm long (6 cm I.D.) PVC columns packed with reconstructed field soil profiles to a depth of 36 cm. Two leaching solutions were, (i) deionized water adjusted to pH 6.5 with nitric acid, and (ii) deionized water adjusted to pH 5.0 with carbon dioxide. Exchangeable metals of the surface soil were determined in IN ammonium acetate extract. In both the runoff water and the leachates, there was greater removal of metals from forested soil than the grass-covered soil. Losses of K and Na far exceeded the losses of Ca and Mg. Release of K was consistent in both sandy and loamy soil plots probably due to K-rich minerals in coastal soils. Slightly high concentrations of Mn, Ni, Zn and Cu and low concentrations of Cd were released by both mechanisms (runoff and leaching), but all were below toxic limits. Removal of trace metals was greater by acidified water than by carbonated water. Ammonium acetate-extractable metals were diminished in the forested soil due to its lower pH than the grass-covered soil. Resutls are important for the maintenance of soil fertility and observing the quality of effluent water to prevent any toxicity.

Principal Investigator: James L. Cooley (University of Georgia)
Principal Investigator: Gail M. Cowie (University of Georgia)

Sponsor: GWRI
Start Date: 1989-04-01; Completion Date: 1989-04-01;
Keywords: watershed protection, watershed management, land use, planning, municipal water, water supply, water quality, water quality management

Description:

In Georgia, recent years have seen an increasing emphasis on watershed protection as a critical component of water supply planning. Effective watershed management requires significant action at the local level. However, many local officials have limited understanding of water quality protection techniques and methods for planning watershed management programs. The objective of this research was development of guidelines, clearly useful to local officials, for watershed protection planning at the local level. Development of guidelines began with a survey of existing watershed protection programs in the Southeast. Preliminary elaboration of a planning process was based on evaluation of thirteen proposed water supply watersheds in Northeast Georgia. The planning process was further refined through detailed analysis of three of these watersheds. Results for the study watersheds are presented with specific discussion of considerations in watershed protection planning.

As defined through this research, the planning process has seven distinct portions: 1) preliminary statement of objectives; 2) watershed assessment; 3) highlighting of areas that require particul~ attention in the management program; 4) refining objectives with public input; 5) definition of alternative watershed protection packages; 6) screening to select the preferred alternative; and 7) planning for implementation and evaluation of program effectiveness. Several components are fundamental to this planning process and make it adaptable to water supply watersheds across north Georgia. First, the process needs to be individually applied to specific watersheds. Second, a variety of technical solutions to watershed protection problems exist. For a watershed protection program to be effective, specific solutions for particular watersheds must be defined by citizens and officials from the locality. Finally, public education and participation is integral to successful application of the watershed protection planning process.

Principal Investigator: Aris Georgakakos (GWRI/Georgia Tech)

Sponsor: GWRI
Start Date: 1988-03-01; Completion Date: 1988-03-01;
Keywords: Streamflow Forecasting, Reservoir Operation, Hydropower, Flood

Description:
The value of streamflow forecasts in reservoir operation depends on a number of factors and may vary considerably. Assessment of forecast benefits is presented here for three specific systems. Statistical streamflow models of increasing forecasting ability are coupled with a recently developed stochastic control method in extensive simulation experiments. The systems’ performance is statistically evaluated with regard to energy generation and flood and drought prevention. The results indicate that forecast benefits are system specific and may range from quite substantial to fairly minimal.

Principal Investigator: John F. Dowd (University of Georgia)
Principal Investigator: Phillip J. Smith (University of Georgia)

p class=IndexItemTitle>Sponsor: GWRI
Start Date: 1988-03-01; Completion Date: 1988-03-01;
class=IndexItemTitle>Keywords: Groundwater, water management, groundwater models, streamflow depletion, induced recharge, seepometer, minipiezometer, temperature

Description:
The objective of this research is to evaluate field methods for estimating streamflow reductions due to pumping from nearby wells. This project is a supplement to previous work which provided a microcomputer model for estimating streamflow depletion due to pumping from nearby wells. Four direct measurement techniques and one indirect estimation technique are described and evaluated for estimating induced recharge through stream bottoms for phreatic and confined aquifers. Direct techniques are seepometers, minipieozmeters, temperature probes, and tracers. The indirect estimate is derived from streamflow correlations. Streamflow correlation estimates and tracers are not generally useful. Seepometers, minipiezometers, and temperature probes are useful for both phreatic and confined aquifers subject to certain bottom sediment and flow volume constraints.

Seepometers, minipiezometers, and temperature probes can be used to measure groundwater discharge from phreatic aquifers through fine-grained and relatively porous bottom sediments such as silts and sands. All three methods require clusters of at least five identical instruments to be installed at each of several measurement points in the stream bottom to properly assess micro- and meso-scale variability in sediment composition and groundwater flux patterns. Seepometers are the easiest to use and directly measure vertical flux through the stream bottom. Minipiezometers require accurate measurements of sediment saturated vertical hydraulic conductivity over the depth sampled, and temperature probes require the measurement of sediment specific heat and specific density and the thermal conductivity of the sediment-fluid complex. None of these three methods can be used in dense clay bottom sediments.

Seepometers and minipiezometers are inappropriate for estimating impacted discharge from confined aquifers. Springs are useful in assessing changes in discharge from confined aquifers. If local conditions do not allow installation of a V -notch wier or other precise instrumentation to directly measure spring discharge, then temperature probes can be used if the discharge volume and temperature gradient are sufficient to change the ambient stream temperature passing the spring during lowflow conditions. Temperature probes are easy to fabricate, install, and automatically monitor.

Principal Investigator: John E. Noakes (University of Georgia)
Principal Investigator: David Wenner (University of Georgia)
Principal Investigator: Gregory C. Simones (University of Georgia)
Principal Investigator: James D. Spaulding (University of Georgia)

Sponsor: GWRI
Start Date: 1988-03-01; Completion Date: 1988-03-01;
Keywords: Elberton, granite, pegmatites, radon, ground water, liquid scintillation

Description:
Our study reveals that the radon (Rn) activity of ground waters is primarily controlled by the geologic setting of the sample site. Neither the sample depth, short term time variations, nor sampling error alter this basic observation. Results from studies in the vicinity of Elberton, Georgia, reveal that ground waters from the main outcrop area of the Elberton Granite Batholith have elevated Rn activities compared to those from adjacent metamorphic terrains to the northwest and southeast. Areas just off the southwest and northeast edges of the main outcrop area of granite, however, yield ground waters with the highest Rn activities. This may be related to the unique geologic setting of these two areas in which small, U-enriched pegmatites lie just below the surface.

Principal Investigator: John E. Noakes (University of Georgia)
Principal Investigator: David Wenner (University of Georgia)
Principal Investigator: Gregory C. Simones (University of Georgia)
Principal Investigator: James D. Spaulding (University of Georgia)

Sponsor: GWRI
Start Date: 1988-03-01; Completion Date: 1988-03-01;
Keywords: Elberton, granite, pegmatites, radon, ground water, liquid scintillation

Description:
Our study reveals that the radon (Rn) activity of ground waters is primarily controlled by the geologic setting of the sample site. Neither the sample depth, short term time variations, nor sampling error alter this basic observation. Results from studies in the vicinity of Elberton, Georgia, reveal that ground waters from the main outcrop area of the Elberton Granite Batholith have elevated Rn activities compared to those from adjacent metamorphic terrains to the northwest and southeast. Areas just off the southwest and northeast edges of the main outcrop area of granite, however, yield ground waters with the highest Rn activities. This may be related to the unique geologic setting of these two areas in which small, U-enriched pegmatites lie just below the surface.

Principal Investigator: Aris Georgakakos (GWRI/Georgia Tech)

Sponsor: GWRI
Start Date: 1988-03-01; Completion Date: 1988-03-01;
Keywords: Streamflow Forecasting, Reservoir Operation, Hydropower, Flood

Description:
The value of streamflow forecasts in reservoir operation depends on a number of factors and may vary considerably. Assessment of forecast benefits is presented here for three specific systems. Statistical streamflow models of increasing forecasting ability are coupled with a recently developed stochastic control method in extensive simulation experiments. The systems’ performance is statistically evaluated with regard to energy generation and flood and drought prevention. The results indicate that forecast benefits are system specific and may range from quite substantial to fairly minimal.

Principal Investigator: John F. Dowd (University of Georgia)
Principal Investigator: Kathryn J. Hatcher (University of Georgia)
Principal Investigator: Phillip J. Smith (University of Georgia)
Principal Investigator: John F. Dowd (University of Georgia)

Sponsor: GWRI
Start Date: 1987-07-01; Completion Date: 1987-07-01;
Keywords: surface-groundwater relationships, groundwater, water management, conjunctive use, wells, regulation, streamflow, groundwater models

Description:
A groundwater model for estimating streamflow reductions due to pumping from nearby wells was developed. The model can be used to evaluate well permit applications for groundwater withdrawals. The computer program is based upon an analytical solution of a two-dimensional planimetric representation of a stream/aquifer system in a semi-infinite domain. The variables required are transmissivity, pumping rate, well location, and aquifer storativity. The program calculates drawdown in the aquifer, drawdown adjacent to the stream, amount of flow induced from the stream into the aquifer, and total contribution from the stream into the well for four time steps per simulation. The program runs interactively on IBM-PC-compatible microcomputers. Results are presented through a summary table and high-resolution graphics when hardware graphics support is available. Output options include line graphs of drawdown along the stream, flow from the stream into the aquifer, and a contour plot of water table drawdown.
The completion report also includes a sensitivity analysis of the computer program for ranges of data likely to be encountered in the southeastern coastal plain is presented. The results illustrate the relative influence of each input parameter and highlight critical data needs for permit evaluation. The results indicate that for many combinations of field conditions and sustained pumping, 90% or more of the total well withdrawal is derived from nearby streams.

Principal Investigator: Shih-Chao Chiang (Georgia Institute of Technology)
Principal Investigator: David E. Radcliffe (University of Georgia)
Principal Investigator: Shih-Chao Chiang (Georgia Institute of Technology)
Principal Investigator: William P. Miller (Georgia Institute of Technology)

Sponsor: GWRI
Start Date: 1987-03-01; Completion Date: 1987-03-01;
Keywords: flocculation, soil erosion, infiltration, permeability

Description:
Lateral movement of infiltrating water frequently occurs at the surface of Southern Piedmont soils and may occur below the surface when dense layers are present at a shallow depth. Our objective was to determine to what extent lateral movement occurred and what mechanisms might be responsible for the low permeability. Because of equipment problems with a field rainfall simulator we were unable to address subsurface lateral flow, but a greenhouse and laboratory experiment provided information on surface lateral flow. In Experiment I., infiltration rates declined steadily in three soils, two of which had final infiltration rates so low that run-off would occur under all but very low intensity rainfalls. The decline in infiltration was attributed to dispersion of soil particles upon impact by raindrops and the formation of a low permeability washed-in layer of dispersed clay particles just below the surface. In Experiment II, it was shown that soil dispersion varied among soils and could be severe when infiltrating water was low in mineral content (eg. rainfall) and soil pH had been raised through liming.