Temporal trend calculation of di (drought index) and comparison of two methods of IDW and KRG as important spatial analysis tools

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Research Paper 01/07/2014
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Temporal trend calculation of di (drought index) and comparison of two methods of IDW and KRG as important spatial analysis tools

Maryam Rashidfar, Hassan Ahmadi, Gholamreza Zehtabian
J. Bio. Env. Sci.5( 1), 385-395, July 2014.
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Abstract

Drought is one of the main natural causes of agricultural, economic and environmental damage. The objective of this study is to provide a comparative spatial analysis by using IDW and KRG methods in Taleghan Watershed in Iran with the view to identifying trends and onset of drought. Data-set is collected from 8 climatology station within the watershed from 1967 to 2008. After testing and if needed normalizing the data, they transformed to the DIP software for calculating the DI. In the second stage we used data in GS+ for assessing the spatial variability of DI Geostatic calculations. To increase certainty, we used cross validation and t-student test to make better decision in choosing best manner for mapping. As results of test, KRG had the highest accuracy compared to the others in making spatial maps. The lack of rain and abnormally dry weather that has happened in 1976 and 1988 was the same and the watershed has been exposed only in extremely dry condition. In addition, for wet period we observed a reverse condition i.e. the area and severity of wet in 2005 is weaker than 1994. In the map of 1994 we can see the extremely wet class in all parts of the watershed, while in the second peak year of wet period, there are moderate, severe and extreme conditions. We can indicate that KRG method for mapping the spatial distribution of climate condition by using the DI can end in a better map than that of IDW method.

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