Temporal trend study of hydrological and meteorological drought in Karkheh watershed

Drought is one of the known environmental phenomenon and impartible part of change climate that occurs in each geographic region. In this study was used Standardized Precipitation Index (SPI) and streamflow drought index (SDI) for assessment and analysis of droughts incidence temporal. For this purpose, were used monthly statistics of 10 rain gauge and 5 hydrometric stations in Karkheh watershed and indicators investigated in 3 timeframes (12, 24, 48 months). At the first, relationship of precipitation and runoff investigated for drought effect study on surface water resources. Then the standardized data rate (SDI) with SPI time series at varies temporal interval using Pearson correlation was studied in the whole of basin and sub basin also compared separately. The results showed that temporal relationship of hydrological and meteorological drought occurrence is meaningful in level of 99 % with together and this correlation is maximum in 48 months. Drought occurrence in case study showed its effect on surface water resources with a delay of 2 months or 1 month that due to the karstic region.