Returning periods of drought and climate change in the Zayandeh Rud River Basin

Abstract

Drought is the result of altered hydrological conditions, in particular, due to precipitation deficit over a period of time, and is one of the most common disasters in all kinds of climate regimes (Chen et al. 2013). Unlike other natural disasters, the effects of drought appear gradually over time, typically on the order of several months to several years. Drought analysis usually involves estimating one of the drought indices and then calculating drought characteristics based on the determined drought index such as severity, duration, and peak intensity (Yang 2010). Among the methods for determining drought characteristics, the threshold value could provide a frame of reference for drought assessment (Yevjevich 1967). As climate change is expected to vary worldwide due to natural and model ambiguities, predicting the impact of climate change on future droughts is vital for water resources management. In the Northern Hemisphere-between 15° and 45° latitudes, including the current study area-drought periods have been particularly severe (Mousavi 2005).