Contribution of two Sioul and Ghadah tributaries in reducing the water quality of the Meimeh River: determination of critical points and remedial solutions

Meymeh River which is located in the southern region of the Ilam Province, Iran, originates from good quality karst aquifer of the Kabir Koh anticline but its water quality decreases during the flow path of the river. The main geological formation at the flow path of the river is Gachsaran formation which partly composed of gypsum and sometimes salty (Halite) rocks. The aim of this study is to determine the contribution of Sioul and Ghadah tributaries in the salinity levels of the Meymeh river water and determining the critical points and also providing remedial solutions for this problem.

In order to determine the locations of quality changes along the Meymeh River, several field visits were arranged and finally 35 sampling stations were determined along the river flow path. Monthly sampling and field measurements were schedualed in the selected stations for measuring the discharge, EC and Temperature for the 2016-2017hyrologic year.  After transferring the water samples to the laboratory, their chemical properties including major cations and anions were measured in the central laboratory of Ilam University.

Meymeh River has several tributaries and its discharge increases gradually. One of its main tributaries is the Sarkadeh River wich collect mainly the water of sulfur spring and Sioul River. The results showed that the Meymeh River quality gradually decreased along its path after originating from the karst formations and entering the Gachsaran formation, (EC at the source and the final station was measured as 500 and 12500 µs/cm, respectively). The results of mass balance showed that 28% Sulfur Springs, 21% Sioul river and 25% gradual changes by Gachsaran formation are effective in the salinity of the Meymeh River. In other words, about 50% of the Meymeh River’s salinity is due to the impact of the Sarkadeh River.

In order to modify the water quality of the Meymeh River, it is necessary to reduce the impact of tributaries which has the highest undesirable effects on the Meymeh River watre quality. Since the Sarkadeh River has the highest impact on the quality of the Meymeh River, the main action was to enhance the water quality of this branch. For this purpose, by constructing channels along the salinity zones of Sioul river, as well as creation of a water transmission pipe line for transfering the water of sulfur springs to the downstream of the Meymeh dam, can reduced more than 50% of the river water salinity and enhance the EC of the Meymeh River from 12500 (current situation) to 5700 µs/cm (doing above activities).