Investigation of relationship between meteorological and hydrological drought in karkheh watershed

Drought is one of the natural disasters which is strongly influenced by climatic fluctuations and makes a set of complex problems in various parts. The aim of this study is investigation of time relationship between meteorological and hydrological drought in Karkhe catchment. To achieve the goal, 26 rain gauge stations and 8 gauging stations were used. In part of research for understanding delay trends in compare with precipitation in real mood, Pearson correlation coefficient between precipitation and discharge was calculated with different time delays. Two indices (SPI and SDI index) were selected for examining Meteorological drought and hydrological drought. Index values in short term step (1 to 3 months), medium-term (6 months) and long term (12 months) was calculated by DrinC software. The results showed that there is 99% direct significant correlation between precipitation-discharge and two SPI-SDI indices in four steps of time. However the correlation coefficient is significant for any four time steps, but the value of correlation coefficient is containing more delay time in a mood that there is not delay time in compare with other cases. Therefore, we can conclude that drought occurs simultaneously in the catchment Karkhe meteorological and hydrological. Also, due to the lack of consistent correlation coefficients and delay time in both cases, two aforementioned indices properly show drought conditions.