Analysis of Steady‐State Salt‐Water Upconing with Application at Truro Well Field, Cape Cod, Massachusetts

Abstract

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.

Estimation of Salt Water Upconing Using a Steady‐State Solution for Partial Completion of a Pumped Well

“…The upconing analysis assumes that flow‐zone thinning is small enough to be excluded from the analysis on the critical rise. To check this assumption, a comparison to the results of Reilly et al (1987) was made. The steady‐state analysis by Reilly et al (1987) used a finite‐element numerical model developed to simulate a sharp salt water‐fresh water interface for determining maximum sustainable well discharges without salt water breakthrough to the pumping well.…”

“…To check this assumption, a comparison to the results of Reilly et al (1987) was made. The steady‐state analysis by Reilly et al (1987) used a finite‐element numerical model developed to simulate a sharp salt water‐fresh water interface for determining maximum sustainable well discharges without salt water breakthrough to the pumping well. Several different comparisons were made with the model, most notably to the results of Bennett et al (1968).…”

“…Reilly's model was also applied to a real world site (no. 4) located on Cape Cod, Massachusetts, where the fresh water lens is in a sandy aquifer, approximately 125 feet (38 m) thick, and underlain by sea water (Reilly et al 1987, figures 4 to 7); other descriptions of the aquifer and the fresh water‐salt water relations include those by LeBlanc et al (1986) and Masterson (2004). Although several scenarios were tested as part of this effort, the most appropriate cases were those with “alternative boundary conditions” using the top boundary as a stream line and the outer radial boundary as a constant potential (i.e., sea level).…”

Effects of Urbanization on Groundwater

“…Saltwater up-coning can be described as the movement of saltwater from a deeper saltwater zone into the fresh groundwater zone in response to reduction of pressures due to pumping at a single well or a well filed (Reilly, Frimpter et al, 1987;. This is a widespread problem that is also observed in coastal aquifers in several states in the USA including Georgia (ASCE, 1969;Krause and Clarke, 2001) as well as globally in other countries.…”

“…This is a widespread problem that is also observed in coastal aquifers in several states in the USA including Georgia (ASCE, 1969;Krause and Clarke, 2001) as well as globally in other countries. The solution of this EFFECTS OF URBANIZATION ON GROUND WATER problem has been attempted using a sharp interface model (Motz, 1992) or the variable density flow analysis approach as discussed above and also in (Reilly, Frimpter et al, 1987;. The most recent work on this line of research is by (Oswald and Kinzelbach, 2004).…”