Analysis of salinity time-trend for the country's surface water resources using the Mankendall method

The electrical conductivity parameters are directly related to the water salinity, and its variation trend indicates the variation trend in water resources salinity. Regarding Iran's water resources, there is a concern that due to climate change and drought in recent years, as well as increased water consumption compared to the past, the quality of these resources in terms of salinity is growing. In this study, the Mankendall trend analysis test by eliminating the discharge background effect (noise), which is a documented method in trend analysis on time series without a specific statistical distribution. In order to find the variation time-trend, the electrical conductivity (EC) parameter was used in 20 hydrometric stations located on different rivers of Iran. In selecting hydrometric stations, climatic, hydrological, land use index and different geographical conditions have been considered as effective factors. The results of this test provide a clearer and more citationable perspective of the salinity process. These results indicate the increasing trend of salinity in Moshiran (Darreh River), Samian (Qarasu River), Ahvaz (Karun River), Doab Nosard (Sirvan River), Maraveh Tappeh (Atrak River) and Nozarabad (Nekaroud River) stations and (30% of selected stations). Among control strategies and reduce this trend are observance of rivers and wetlands, balancing and reducing withdrawal from groundwater resources, implementation of watershed management projects, drainage management and prevent the development of agriculture.