Geology topics

A.S. Goodman

Publications and source records attributed to A.S. Goodman.

3 recordsLinked to original sources

USGS2006

Analysis of steady-state salt-water upconing with application at Truro well field, Cape Cod, Massachusetts

Salt-water upconing describes the phenomenon where salt water is transported vertically upward under a well in response to pumpage in a fresh-water aquifer underlain by salt water. Sharp interface methods have been used successfully to describe the physics of upconing. A finite-element model is developed to simulate a sharp interface for determination of the steady-state position of the interface and maximum permissible well discharges. The model developed is compared to previous published electric-analog model results of Bennett and others (1968). Both methods are applied to a test case at Truro, Massachusetts, where maximum permissible discharges are determined by the finite-element model to range from 0.47 to 1.05 cubic feet per second for the Test Site No. 4 location.

Groundwater↗

USGS1987

Analysis of saltwater upconing beneath a pumping well

Aquifer systems that contain freshwater and saltwater are usually stratified, with the more dense saltwater underlying the freshwater. A groundwater well discharging from the freshwater zone causes the saltwater to move upwards towards the well. This phenomenon is known as saltwater upconing. Two methods of analysis, the sharp-interface method and the fluid-density-dependent solute-transport method, are used to simulate saltwater upconing. Numerical experiments including comparisons of the two methods indicate: (1) for low to moderate pumpages the 50% isochlor and sharp interface correlate well; (2) the well can discharge significant concentrations of saltwater, even though a stable cone (according to the sharp-interface method) exists below the well screen; (3) an almost linear relationship exists between the well discharge rate and the concentration of the discharge at low pumping rates that maintain a stable cone; and (4) upconing is sensitive to transverse dispersivity, whereas it is insensitive to longitudinal dispersivity. A simulation of upconing at Test Site No. 4, Truro, Cape Cod, Massachusetts, indicates that the appropriate field value of transverse dispersivity is very small. This supports the validity of the sharp-interface assumption for analyzing the behavior of systems with thin saltwater-freshwater transition zones.

Journal of Hydrology↗

USGS1985

Quantitative analysis of saltwater-freshwater relationships in groundwater systems-A historical perspective

Although much progress has been made toward the mathematical description of saltwater-freshwater relationships in groundwater systems since the late 19th century, the advective and dispersive mechanisms involved are still incompletely understood. This article documents the major historical advances in this subject and summarizes the major direction of current studies. From the time of Badon Ghyben and Herzberg, it has been recognized that density is important in mathematically describing saltwater-freshwater systems. Other mechanisms, such as hydrodynamic dispersion, were identified later and are still not fully understood. Quantitative analysis of a saltwater-freshwater system attempts to mathematically describe the physical system and the important mechanisms using reasonable simplifications and assumptions. This paper, in developing the history of quantitative analysis discusses many of these simplifications and assumptions and their effect on describing and understanding the phenomenon.

Journal of Hydrology↗