Investigating the Relationship between Hydrological Drought and the Electrical Conductivity of the River in the Downstream Stations of the Karkheh River

This research was conducted with the aim of investigating the effect of hydrological drought periods on the electrical conductivity of water in selected stations of the southern part of the Karkheh River. Mann-Kendall test was used to assess the trend of the data and Petit test was used to determine the break points in the data. The results of Petit's test for electrical conductivity parameter indicated a failure in the data trend in 1996 and 1997 in different stations. Because of meteorological drought, the electrical conductivity has been increased and at the same time a sharp decrease in discharge is recognizable. Although, the trend of SDI index has not always been accompanied by the trend of increasing EC. In addition, the increase in electrical conductivity in Karkheh Dam’s downstream stations is probably due to the dam regulatory flow decreasing. By observing the break point in the time series of discharge and electrical conductivity in 1997, it was fund that the occurrence of drought and as a result the increase in salinity occurred before the dam impoundment. Also, after that, there is no significant change in electrical conductivity in Abdulkhan and Paypol stations. It seems that the Karkheh dam was not the most effective factor in the increase of EC in the downstream stations after its operation, and reducing the discharge and, as a result, increasing the salinity of the South Karkheh area can be considered as a result of the increase in drought and consumption in the upstream regions.