Mathematical Model of Salinity Intrusion in the Arvand Tidal River and Its Effect on Salinity of Lands around the River

An increase in soil and water salinity is one of the world’s problems that are an obstacle to economic and agricultural development. The Arvand river (Shatt Al-Arab), one of the most critical border rivers, is facing a significant decrease in the quality of water and soil due to the intrusion of salty water from the Persian Gulf, which is considered a severe threat to the region. It is formed from the intersection of the Tigris and Euphrates rivers and finally flows into the Persian Gulf. In the current research, the simulation results determined that in the average inflow conditions of Arvand, the saline front penetrates the river up to 60 km from the downstream and affects the river’s water quality. Then the effect of river water salinity on soil salinity was done from two aspects, soil salinity by direct infiltration from riverbanks and soil salinity by long-term use of river water for irrigation. The results showed that in 188 km from the upstream of the river, up to 242 meters, saline water affects the soil on both sides of the river, and in the south of Abadan, this saline band disappears. The prediction of land salinity by irrigation with river water in steady conditions showed that the average salinity of saturated soil extract in Iran in Al-gasbah and in Iraq south of Faw region reaches 97.3 ppt.