Marziye Sadat Mirahsani; Abdolrasol Salman Mahini; Reza Moddares; Alireza Soffianian; Reza Jafari; Jahangir Mohhamadi
Abstract
Zayandeh Rood Basin has a vital role in Iran's poetry, biomass, agriculture, industry and tourism, faced with drought problems. Clustering approach can be a management approach to reduce drought risk impacts which groups the members with regard to the division based on the Euclidean distance of stations. ...
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Zayandeh Rood Basin has a vital role in Iran's poetry, biomass, agriculture, industry and tourism, faced with drought problems. Clustering approach can be a management approach to reduce drought risk impacts which groups the members with regard to the division based on the Euclidean distance of stations. In this research, the approach of determining the spatial-temporal distribution of drought clusters in watersheds is used to express variations based on precipitation precipitation index (SPI) parameters of stations, which depends on the probability of precipitation for any time scale. Since the maximum spatial distribution of the meteorological stations in the region and the maximum time period of the long-term and possible long-term statistical period were considered the same, the data of 26 stations from 12 years (2003 to 2014) was used as reference data. In this regard, the12 months SPI index was first calculated. Then, the 12-month SPI index, which ended in December, was used for cluster analysis of the SPI, and then 144 data were clustered into four groups. Further, zoning analysis was performed on data clusters. Then, the relationship between elevations as an effective landform factor in drought with SPI drought index cluster was investigated using correlation of variables. SPI correlation with mean height of each cluster stations was studied and the results were compared and analyzed. The results of the SPI drought fluctuation chart showed a very severe drought in 2008 and 2009 and 2010, and severe drought in 2010 and mild drought in 2003, 2005 and 2013. Also, 12-month SPI drought data showed a high and negative correlation with height data. Consequently, spatial-temporal monitoring of drought indicators clusters is recommended as a way to manage the impacts of drought risk.
Alireza Shokoohi; Reza Morovati
Abstract
The Lake Urmia is the 20th largest lake and the second hyper saline lake in the world. In recent years, the drying out of the Urmia Lake has attracted attention of many researchers. The main motivation of this study is to evaluate the role of drought in this disaster. For this purpose, Standardized Precipitation ...
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The Lake Urmia is the 20th largest lake and the second hyper saline lake in the world. In recent years, the drying out of the Urmia Lake has attracted attention of many researchers. The main motivation of this study is to evaluate the role of drought in this disaster. For this purpose, Standardized Precipitation Index (SPI) and Reconnaissance Drought Index (RDI) are employed. The data for analysis including precipitation and temperature was provided from two global databases: GPCC for precipitation and NCEP/NCAR for temperature. The study was performed at the time span of 1980-2010 and the results showed that the Lake Urmia basin has experienced a severely drought during 1999-2000. After this period and during eight subsequent years, the negative effects of this drought could not be reduced completely by near normal to wet condition of the basin. Moreover, another severely drought occurred at 2008. RDI value for the 1999 drought was found to be -2.23 which is related to the extremely dry condition. The value of SPI for the same region and same year was obtained as -2.13. This comparison for other severe and extreme cases shows that RDI is more sensitive than SPI at the tails of the phenomenon. It was also observed that after 2000, while the region, in terms of rainfall and drought conditions, is generally close to normal condition, the lake follows a continuous decreasing trend up to the present time. Therefore, one can conclude that in addition to drought, other factors contribute to the drying out of the lake. The results indicated that the anthropogenic effects are responsible to some percent in this disaster. Construction of reservoir dams for agricultural development and other activities for job creation purposes like constructing fish ponds has intensified this crisis. The span of these activities is concurrent to the periods which the drought indices show the fragile condition of the basin in terms of available water resources. This fact emphasizes the importance of drought monitoring as an inseparable part of an IWRM program to prevent a nationwide disaster.
