Nonparametric Test of Spatio -Temporal Changes of Rainfalls in Isfahan Province During the Last Three Decades

Document Type : Research Paper

Author

Associate Professor, Department of Geography, Faculty of Humanities, University of Meybod, Meybod, Iran.

10.29252/aridbiom.2026.4247

Abstract

The water crisis in Iran represents a critical environmental challenge, driven primarily by rainfall deficits, unfavorable spatiotemporal precipitation distribution, and a declining trend in recent decades. This study investigates the spatiotemporal distribution of rainfall across Isfahan province over a 30-year period (1996–2025). Rainfall trends were initially evaluated using the non-parametric Mann-Kendall and Sen's slope estimator tests. Subsequently, by analyzing shifts in monthly precipitation regimes across various stations, a spatial distribution map of rainfall trends (Z-statistic) was generated via GIS interpolation techniques. The findings indicate that while the overall provincial annual rainfall trend remained relatively stable with a baseline Z-statistic of 0.11, the spatial distribution of the Z-statistic reveals that the eastern, northern, and southern regions of Isfahan province are significantly more vulnerable to climate change, exhibiting a more severe decline in precipitation. Furthermore, the analysis demonstrates that the Z-statistic values operate independently of long-term annual rainfall volumes, with negative precipitation trends manifested across both high-rainfall and low-rainfall zones of the province. Crucially, a comparative analysis of monthly rainfall revealed opposing trends in March and May, which exhibit significant downward (negative) and upward (positive) trajectories, respectively. This structural shift highlights a critical alteration in Isfahan's precipitation regime, characterized by a seasonal migration of rainfall from winter to spring.

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References

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Journal of Arid Biome
Volume 16, Issue 1
March 2026
Pages 57-70

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