Reliability, resilience, and vulnerability of Chalous Watershed based on drought index

Drought is one of the natural disasters related to climate and one of the most important threats to human survival leading to adverse effects on social, economic, and environmental sustainability. In this study, it has been tried to evaluate the changes in reliability, resilience, and vulnerability of the Chalous Watershed under the influence of drought in the period of 1982-2017. In this vein, rainfall data of nine stations were interpolated using invers distance squared method to the whole watershed. The SPI drought index was then determined through determining the mean and standard deviation of the data. To calculate Rel, Res and Vul indices, the mean value of SPI Index was used. By calculating the geometric mean value of these indicators, the general health status of the watershed was determined and quantified. The results showed that the SPI Index in this period varied between -1.43 and 2.25. Drought index had a similar pattern to that of rainfall with an increasing trend at the end of the period. The watershed health assessment also showed that the indicators of reliability, resilience, and vulnerability were found 0.5, from 0.23 to 0.62 and from 0.06 to 1, respectively. The geometric mean of these indices was also ranged between 0.19 and 0.58. The overall health condition of the Chalous Watershed based on the dynamics of drought index with a mean index of 0.45 was classified as “moderate”. The findings of the current research will play an important role in explaining the methods of adaptive management of the watershed.