Document Type : Original Article
Authors
1
Ph.D. Graduate, Department of Desertification, Faculty of Desert Studies, Semnan University, Semnan, Iran.
2
M.Sc. Graduate, Department of Natural Resoources, Isfahan University of Technology, Isfahan, Iran.
10.22075/ceasr.2025.37883.1051
Abstract
Introduction and Objectives: Meteorological drought is a critical issue in semi-arid regions, impacting agriculture, water resources, and ecosystems. The Damghanrud Basin in Semnan Province, with its arid climate and reliance on seasonal rainfall, is highly vulnerable to climatic variability. This study aimed to assess multi-scale drought patterns using the Standardized Precipitation Index (SPI) over a 30-year period.
Materials and Methods: Monthly precipitation data (1990–2020) from three meteorological stations representing different land uses and microclimates were analyzed. Data quality was tested using the Shapiro–Wilk test (normality), Pettitt test (homogeneity), and IQR method (outlier detection). Anomalies were corrected by interpolation. SPI values were calculated at 1-, 3-, 6-, 12-, 24-, and 48-month scales using a gamma distribution and converted to standard normal. Drought (SPI < -1) and wet (SPI > 1) periods were identified in R software. Spatial variability was assessed based on topography and land use.
Results and Discussion: Drought patterns varied across stations due to microclimatic and land use differences. Damghan station showed short-term droughts in late winter–spring, affecting planting. Fooladmahaleh experienced autumn–winter droughts, reducing soil moisture. Chahardeh Damghan, in a drier zone, had spring–summer droughts impacting vegetation. Medium-term droughts were persistent, and long-term droughts, while rare, were severe—posing risks to groundwater-dependent ecosystems. Limitations include limited station data and lack of temperature or socio-economic variables.
Conclusion: SPI analysis confirmed Damghan’s drought vulnerability. The diverse drought effects highlight the need for localized water management. Future studies should use satellite data, multiple drought indices, and hydrological models for improved drought assessment.
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