Document Type : Original Article
Author
Department of Geography, Faculty of Literature and Humanities, Sayyed Jamaleddin Asadabadi University, Asadabad, Iran
10.22034/iwm.2026.2076790.1252
Abstract
Extended Abstract
Introduction: Today, climate change has widespread impacts on human life and its natural environment, to the point that some researchers consider this phenomenon one of the most important global threats of the 21st century. By affecting factors such as temperature, evapotranspiration, and precipitation, climate change has accelerated the severity of droughts and imposed sudden stresses on most human, animal, and plant ecosystems. This ultimately leads to a shortage of water resources; the drying up of lakes, rivers and wetlands, a decrease in groundwater levels, land subsidence, a decline in water quality, soil erosion, desertification; and an increase in dust storms in the country. Therefore, the main goal of this research is to study climate behavior in the drainage basins of Iran to reveal the trends of climate elements and analyze environmental crises caused by climate change.
Materials and Methods: In the present study, daily precipitation, temperature, and humidity data from synoptic and climatological stations with at least 50 years of statistical data were used to analyze the climate of 6 major Iranian drainage basin (level 1 basins) in the last half century. The data, covering the period from 1975 to the end of 2024, were obtained from the National Center for Climate and Drought Crisis Management. Following statistical analysis, temporal and spatial analyses were conducted. Graphic diagrams of temperature, precipitation, and evapotranspiration were generated, and drought maps were extracted based on the Standardized Precipitation Index (SPI) separately for all major drainage basins of the country.
Results and Discussion: The results showed that the dominant climate pattern in Iran over the last 50 years has been an increasing trend in temperature and evapotranspiration, along with a decreasing trend in precipitation in many regions. Over the last half century, the annual temperature trend in the country has increased by about 0.41 °C per decade, which is higher than the global average. Furthermore, the trend of potential evapotranspiration in Iran indicates that this parameter has been increasing at a rate of 13.5 mm per year. Precipitation has also changed significantly and has become anomalous. This change is clearly evident both on a decadal scale and in annual time series, with the rainfall trend decreasing by 1.1 mm per year. The climatic analysis of Iran's drainage basins over the last half century revealed that the Caspian Sea watershed has been experiencing severe drought, with 37% of the basin area affected. In the Persian Gulf and Oman Sea basins, severe droughts have affected more than 50% of the basin area. In the Lake Urmia basin, a mountainous hub in the northwest, the share of severe drought is 47%. In the Central Plateau watershed, the largest in Iran, the share of wet years is near zero, while droughts cover close to 80% of the basin area. In the border watershed of eastern Iran, droughts cover 60% of the basin area. In the Qaraqom (Sarkhs) watershed, very severe droughts account for 44% of the area. It appears that drought in Iran is not limited to the inland and low-rainfall regions; the possibility of this phenomenon occurring in any climate (even the high-rainfall Caspian regions) exists. In the last half century, drought in Iran has both intensified and spread, penetrating even the northern, northwestern, and western halves of the country. Meanwhile, wet years are increasingly concentrated, following a phenomenon of climatic nesting. This situation confirms the role of increasing global warming and climate change.
Conclusion: Iran's specific geographical location—being situated in a hot and dry region of the planet, adjacent to the Lut Desert and central deserts, and distant from moisture-rich sources—has caused the amount of precipitation in Iran to be much lower than the global average. Today, increasing global warming and climate change have exacerbated the arid and drought conditions in the country. Therefore, increasing temperatures on one hand and decreasing precipitation on the other can lead to a reduction in surface water storage, a decrease in soil moisture retention, an increase in evaporation, and ultimately a water shortage and drought crisis. In addition, the distance from moisture sources, the proximity to internal deserts, and the location in the rain shadow of the Zagros and Alborz mountain ranges have caused Iran's drainage basins to suffer from severe drought and water crises.
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