Impact of Dam Construction on Duration and Magnitude of Drought (Case Study: Karkheh River)

Today’s drought and dehydration have become one of the great problems of the country and as a solution; several dams have been established in different regions of Iran to combat that. Typically, hydrological drought is affected by climate change and human activities, which has been studied with respect to climate change and its relation to drought, but the impact of human activities on droughts has been less widely considered. Therefore, in this research has tried to investigate the effect of Karkhe dam construction on occurrence of hydrological droughts. To achieve the research objectives, information was obtained from 14 hydrometric stations and 19 Rain gauge station which had long-term data of 30 years. First, hydrological drought was calculated using SDI and meteorological drought using SPI index. Then, in order to answer the research question, the regression relations, the analysis of the boxplot in SPSS software and descriptive statistics of droughts were analyzed by two statistical periods before and after the construction of the dam. The results showed that, before the dam was constructed, the magnitude and duration of hydrological droughts in the upper regions of the catchment area was higher, but with dam construction, the magnitude and duration of droughts in the bottom of the dam increased. These results indicate the negative impact of the dam on the Karkheh River. Therefore, Karkheh dam can not only reduce the hydrological droughts of the area but also increase them.