Determination of drought Using Multi Criteria Decision Making Based on TOPSIS Method (A case study of selective Isfahan Province Stations)

This research was aimed to classify the drought in arid and semi arid regions of Isfahan province using TOPSIS technique. Four climatic elements including temperature, number of rainy days, annual rainfall and relative humidity were used for five meteorological stations during the 20-year period (1994-2013). For validation of the proposed method, the output of TOPSIS method was compared with the output of DPI, PNPI, RAI and SPI. For this purpose, Spearman's rank correlation coefficient was used between the quantified values of drought severity index and annual rainfall. The results showed that there was a strong correlation between the drought severity index and annual rainfall in the TOPSIS algorithm in all studied stations. Therefore, the validity of the model was approved. Generally, moisture fluctuations are high in the study area. In other words, drought is completely independent from station to station and from year to year, so that Nain and Isfahan had the highest (13 years) and lowest (7 years) number of drought years, respectively. In the TOPSIS algorithm, drought is closer to its real value since more parameters are used compared with previous simple methods. In this method, there is a systematic relationship between climatic elements in a year and other years, through which evaluation and ranking of drought is carried out. Finally, it could be concluded that the TOPSIS algorithm is a method capable of determining and ranking drought.