Analysis of Spatial and Temporal Changes in the Water Salinity (EC) Along the Meymeh River via the SWAT Semidistributed Model and Field Data

ABSTRACT The objective of this study is to examine the causes of the decrease in river water quality along the path and to determine the locations where quality changes occur in the Meymeh Basin, west of Iran, so that, if possible, solutions can be provided to prevent the river from becoming salty. The hydrological model of the basin was developed via the semidistributed SWAT model to calculate the water budget and yield of the subbasins. Then, to check the salinity and salt balance of the subbasins and main river reaches, field data and salt load calculations are utilized. Model sensitivity analysis, calibration and validation were carried out via the SUFI‐2 program. The results show that the average EC value of both periods at the origin of the Meymeh River (Kilometre 0) was 0.021 S/m. From the origin up to km 68, despite the addition of the Sarab‐e‐Gorab, Shahr‐e‐mir, Kharbozan and Vorazan tributaries to the main river, all of which have EC values higher than those of the main river, the rate of increase in the salinity of the river in both dry and wet periods occurred with a gentle slope, and at km 68, it reached an average value of 0.028 S/m.