Monitoring of drawdown pattern during pumping in an unconfined physical aquifer model

Seoung Sup Lee, Joung Souk Kim, Dong Ju Kim

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

In this study, we attempted to analyse a drawdown pattern around a pumping well in an unconfined sandy gravelly aquifer constructed in a laboratory tank by means of both experimental and numerical modelling of groundwater flow. The physical model consisted of recharge, aquifer and discharge zones. Permeability and specific yield of the aquifer material were determined by Dupuit approximation under steady-state flow and stepwise gravitational drainage of groundwater, respectively. The drawdown of water table in pumping and neighbouring observation wells was monitored to investigate the effect of no-flow boundary on the drawdown pattern during pumping for three different boundary conditions: (i) no recharge and no discharge with four no-flow boundaries (Case 1); (ii) no recharge and reservoir with three no-flow boundaries (Case 2); (iii) recharge and discharge with two no-flow boundaries (Case 3). Based on the aquifer parameters, numerical modelling was also performed to compare the simulated drawdown with that observed. Results showed that a large difference existed between the simulated drawdown and that observed in wells for all cases. The reason for the difference could be explained by the formation of a curvilinear type water table between wells rather than a linear one due to a delayed response of water table in the capillary fringe. This phenomenon was also investigated from a mass balance study on the pumping volume. The curvilinear type of water table was further evidenced by measurement of water contents at several positions in the aquifer between wells using time domain reflectometry (TDR). This indicates that the existing groundwater flow model applicable to an unconfined aquifer lacks the capacity to describe a slow response of water table in the aquifer and care should be taken in the interpretation of water table formation in the aquifer during pumping.

Original languageEnglish
Pages (from-to)479-492
Number of pages14
JournalHydrological Processes
Volume15
Issue number3
DOIs
Publication statusPublished - 2001 Feb 28

Keywords

  • Drawdown
  • Pumping
  • TDR
  • Unconfined aquifer
  • Water content
  • Water table

ASJC Scopus subject areas

  • Water Science and Technology

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