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Volume 41, Issue 2 (2026)
GeoRes 2026, 41(2): 141-148 |
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Received: 2026/06/16 | Accepted: 2026/09/7 | Published: 2026/09/19
Received: 2026/06/16 | Accepted: 2026/09/7 | Published: 2026/09/19
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Javadeein S, Behzadi J, Amiri E, Moghimi A. (2026). Short- and Long-Term Dry Periods in Lahijan and Their Implications for Water Resources. , GeoRes. 41(2), 141-148. doi:10.58209/geores.41.2.141
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1- Department of Water Engineering, La.C. (Lahijan Campus), Islamic Azad University, Lahijan, Iran
Abstract (433 Views)
Aims: Drought and short- and long-term wet and dry periods are among the most important effects of climate change on precipitation. This study determined the severity, frequency, and timing of dry periods in Lahijan and examined their spatial distribution in Gilan Province.
Methodology: This study used time-series analysis of precipitation. Thirty years (1994-2023) of monthly precipitation data from the Lahijan station and 14 other stations in Gilan Province were analyzed. Dry periods were identified with the Standardized Precipitation Index at 3- and 36-month scales, precipitation trends with the Mann-Kendall test, and the spatial distribution of dryness by interpolation in a geographic information system.
Findings: Mean annual precipitation in Lahijan was 1491.2±270.3mm, and autumn received 41% of it. Seasonal fluctuations in precipitation exceeded annual fluctuations. Twenty-five 3-month dry periods lasting 2 to 12 months occurred, with a maximum intensity of -2.7. Two 36-month dry periods were recorded; the most intense and longest lasted from October 2016 to June 2023 (81 months) with an intensity of -2.39. Most dry periods occurred in eastern and central Gilan, including Lahijan.
Conclusion: 36-month dry periods are less frequent but more intense and longer than 3-month periods. Short-term dry periods affect agriculture, and long-term dry periods affect water resources. Agricultural water planning and water resource protection in Lahijan must take these periods into account.
Methodology: This study used time-series analysis of precipitation. Thirty years (1994-2023) of monthly precipitation data from the Lahijan station and 14 other stations in Gilan Province were analyzed. Dry periods were identified with the Standardized Precipitation Index at 3- and 36-month scales, precipitation trends with the Mann-Kendall test, and the spatial distribution of dryness by interpolation in a geographic information system.
Findings: Mean annual precipitation in Lahijan was 1491.2±270.3mm, and autumn received 41% of it. Seasonal fluctuations in precipitation exceeded annual fluctuations. Twenty-five 3-month dry periods lasting 2 to 12 months occurred, with a maximum intensity of -2.7. Two 36-month dry periods were recorded; the most intense and longest lasted from October 2016 to June 2023 (81 months) with an intensity of -2.39. Most dry periods occurred in eastern and central Gilan, including Lahijan.
Conclusion: 36-month dry periods are less frequent but more intense and longer than 3-month periods. Short-term dry periods affect agriculture, and long-term dry periods affect water resources. Agricultural water planning and water resource protection in Lahijan must take these periods into account.