PUMPING TEST ANALYSIS FOR A TIDALLY FORCED AQUIFER

Citation
Mg. Trefry et Cd. Johnston, PUMPING TEST ANALYSIS FOR A TIDALLY FORCED AQUIFER, Ground water, 36(3), 1998, pp. 427-433
Citations number
13
Categorie Soggetti
Water Resources","Geosciences, Interdisciplinary
Journal title
ISSN journal
0017467X
Volume
36
Issue
3
Year of publication
1998
Pages
427 - 433
Database
ISI
SICI code
0017-467X(1998)36:3<427:PTAFAT>2.0.ZU;2-I
Abstract
The analysis of pumping test data for a shallow riverbank aquifer affo rded the opportunity to compare standard methods for determining hydra ulic conductivity (K) and storativity (S) with techniques based on the propagation of periodic fluctuations of head in the aquifer. Tidal fl uctuations in water level at the riverbank were found to propagate app roximately nondispersively for 200 m in the aquifer, allowing tidal ph ase lags and amplitude attenuations in the aquifer to be estimated fro m river levels by least-squares techniques. The least-squares attenuat ions and phases were used to correct measured pumping test drawdowns f or tidal influences. Standard transient analyses of the corrected draw downs were performed, yielding values of approximately 8 to 10 m/d for K and 0.002 for S. The low S value was taken to indicate semi-confine d conditions. The tidal attenuation coefficients were used to determin e the hydraulic diffusivity T/S, providing values that were integrated over the distance from the riverbank to the relevant monitoring wells . S values from the drawdown analyses then yielded K estimates ranging from 3 to 7 mid. A three-dimensional finite-element simulation of the pumping tests showed that the estimated K and S values yielded simula ted drawdowns in reasonable agreement with field observations.