Journal of Ecohydrology

Journal of Ecohydrology

Multivariate Groundwater Quality Analysis of Qazvin Aquifer Using Archimedean & Elliptic Copula Functions

Document Type : Research Article

Authors
Mohammad Mofidi 1
Farhad Hooshyaripor 2
Hamid Kardan moghaddam 3
Roohollah Noori 4
1 Department of Civil Engineering, SR.C., Islamic Azad University, Tehran, Iran
2 Corresponding author, Department of Civil Engineering, SR.C., Islamic Azad University, Tehran, Iran
3 Water Research Institute (WRI), Ministry of Energy, Tehran, Iran
4 Graduate Faculty of Environment, University of Tehran, Tehran, Iran
10.22059/ije.2026.415928.1916
Abstract
Objective: Groundwater resources in arid and semi-arid regions of Iran, including the Ghazvin Aquifer, are increasingly affected by overexploitation and climate change. This study aims to provide a spatial multivariate assessment of contamination in the Ghazvin Aquifer by using the Groundwater Quality Index (GWQI) in 28 pizometers and Copula functons.
Method: Text. Text. Authors are encouraged to use AI for grammar checking to enhance derived from eleven hydrochemical parameters: Na⁺, K⁺, Mg²⁺, Ca²⁺, SO₄²⁻, Cl⁻, HCO₃⁻, pH, TDS, EC, and TH. Six copula families—Gaussian, Student’s t, Clayton, Frank, Joe, and Ali–Mikhail–Haq (AMH)—were applied. The dataset included observations from 28 piezometers distributed across the Ghazvin Plain over the period 2006–2022. Using data from multiple piezometers, copula functions were employed to investigate the spatiotemporal characteristics of the contamination index across the study area.
Results: The results showed that the AMH, Clayton, and Frank copulas provided the best performance. The joint return periods, TAND=11.11 years and TOR=1.73 years, showed a 6.4-fold difference, confirming that univariate approaches systematically underestimate risk.
Conclusions: The findings suggest that conditional copula functions can be effectively used for probabilistic spatiotemporal assessment of groundwater contamination risk in aquifer systems
Keywords
Ghazvin Aquifer
Joint probability
Copula function
Conditional return period
Water contamination index
Subjects
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Journal of Ecohydrology
Volume 13, Issue 3
Summer 2026
Pages 1433-1453

  • Receive Date 11 July 2026
  • Revise Date 06 August 2026
  • Accept Date 24 August 2026
  • First Publish Date 24 August 2026
  • Publish Date 23 September 2026