Use of time–subsidence data during pumping to characterize specific storage and hydraulic conductivity of semi-confining units
2003; Elsevier BV; Volume: 281; Issue: 1-2 Linguagem: Inglês
10.1016/s0022-1694(03)00197-5
ISSN1879-2707
Autores Tópico(s)Groundwater flow and contamination studies
ResumoA new graphical technique is developed that takes advantage of time–subsidence data collected from either traditional extensometer installations or from newer technologies such as fixed-station global positioning systems or interferometric synthetic aperture radar imagery, to accurately estimate storage properties of the aquifer and vertical hydraulic conductivity of semi-confining units. Semi-log plots of time–compaction data are highly diagnostic with the straight-line portion of the plot reflecting the specific storage of the semi-confining unit. Calculation of compaction during one-log cycle of time from these plots can be used in a simple analytical expression based on the Cooper–Jacob technique to accurately calculate specific storage of the semi-confining units. In addition, these semi-log plots can be used to identify when the pressure transient has migrated through the confining layer into the unpumped aquifer, precluding the need for additional piezometers within the unpumped aquifer or within the semi-confining units as is necessary in the Neuman and Witherspoon method. Numerical simulations are used to evaluate the accuracy of the new technique. The technique was applied to time–drawdown and time–compaction data collected near Franklin Virginia, within the Potomac aquifers of the Coastal Plain, and shows that the method can be easily applied to estimate the inelastic skeletal specific storage of this aquifer system.
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