Spatiotemporal investigation of drought pattern in Iran via statistical analysis and GIS technique
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ORIGINAL PAPER
Spatiotemporal investigation of drought pattern in Iran via statistical analysis and GIS technique Mehdi Bahrami 1
&
Samira Bazrkar 1 & Abdol Rassoul Zarei 2
Received: 16 August 2019 / Accepted: 23 November 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Drought monitoring is very important for water resource planning due to the impact of climate change on the frequency of drought events. The objective of this study was to evaluate the spatiotemporal characteristics of drought in Iran. Spatial and temporal distributions of drought severity were assessed using the well-accepted standardized reconnaissance drought index (RDIst) in seasonal and annual scales in 40 synoptic meteorological stations of Iran during the years 1967–2014. Parametric and nonparametric statistical tests were further used for trend assessments. According to the results of RDIst on an annual time scale, the trends of drought were positive in 87.5% of the stations. The results of seasonal RDIst also indicated that the trends of drought in winter (92.5%), spring (82.5%), summer (37.5%), and fall (67.5%) were upward. In sequence series of all seasons, 90% of all stations had a negative trend in the value of their calculated RDIst over time, which means an upward trend in drought over time. Our findings demonstrated an upward trend in drought over the study period. In 45% of the studied stations, winter had the most significant positive trend at all time scales. The results also showed that a moderate drought covered the highest portion of the study area. Generally, a positive trend was observed in coverage of extreme, severe, and moderate drought. However, a negative trend was evident in the coverage of extreme, severe, and moderate wet conditions during the time. It is suggested that the spatiotemporal distribution of the RDIst trend can be used to identify drought and mitigate its impacts in Iran. Keywords Drought . GIS . Iran . Spatiotemporal distribution . Standardized RDI
1 introduction Drought is a natural phenomenon, which is defined as a sustained and regionally extensive incidence of belownormal natural water availability (Tallaksen and Van Lanen 2004). Drought has large impacts on economies, societies, and the environment. Changes in drought frequency, duration, and severity have vast impacts on the hydrological cycle, water
* Mehdi Bahrami [email protected] Samira Bazrkar [email protected] Abdol Rassoul Zarei [email protected]; [email protected] 1
Department of Water Engineering, Faculty of Agriculture, Fasa University, Fasa, Iran
2
Department of Range and Watershed Management (Nature Engineering), Faculty of Agriculture, Fasa University, Fasa, Iran
management, and agricultural production. So, one major concern arising from climate change is its potential effects on water resources (Nam et al. 2015). Drought classified into four categories, including meteorological, agricultural, hydrological, and socioeconomic (Wilhite and Glantz 1985; Dracup et al. 1980). The Palmer
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