Analytical and numerical analysis of constant-rate pumping test data considering aquifer boundary effect

Luminda Niroshana Gunawardhana*, Fatma Al-Harthi, Ahmed Sana, Mahad Said Baawain

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The constant-rate pumping test (CRT) is commonly used to determine the aquifer properties. In this method, measured drawdown in the pumping well and the monitoring wells are usually matched with type curves developed by various analytical methods. However, numerous assumptions used to develop the analytical solution are not always compatible with the actual site conditions. In this study, drawdown records collected in a pumping well and two monitoring wells located near a river, were analyzed to investigate the boundary effects on the estimated aquifer properties. This site condition violates the assumption that the aquifer is of infinite areal extent. Moreover, time varying water heads during the pumping and recovery tests were simulated numerically to determine the effect of hydraulic gradient, which does not satisfy the assumption of horizontal potentiometric surface used in the analytical solution. Calibrated aquifer properties without the boundary effect showed clear differences, where the transmissivity, anisotropy ratio and specific yield varied by 12%, 34% and 53%, respectively, as compared to the results obtained by including the boundary effect. Numerical simulation conducted by considering a horizontal potentiometric surface as in the analytical model produced an averaged root-mean-squared-error (RMSE) of 0.055 m, which was approximately 57% higher than the RMSE value estimated with the effect of the hydraulic gradient. Therefore, it was concluded that the simplified analytical solutions may lead to misleading estimations of aquifer properties when the pumping test was conducted in an area with complex site conditions.

Original languageEnglish
Article number543
JournalEnvironmental Earth Sciences
Volume80
Issue number17
DOIs
Publication statusPublished - Sep 2021

Keywords

  • MODFLOW
  • Oman
  • Partially penetrating well
  • River boundary
  • Unconfined aquifer

ASJC Scopus subject areas

  • Global and Planetary Change
  • Environmental Chemistry
  • Water Science and Technology
  • Soil Science
  • Pollution
  • Geology
  • Earth-Surface Processes

Cite this