Salinization of Karun River in Iran by shallow groundwater and seawater encroachment

Abstract

Karun is the largest and the longest river in Iran which flows down the Zagros mountain range and into the Khuzestan plain. The river winds its way through this flat alluvial plain until it reaches the Persian Gulf. Karun enjoys a reasonably good drinking quality at the point of entry to Khuzestan plain, but after collecting agricultural, municipal and industrial effluents, uptake for irrigation and domestic use, and groundwater intrusion, its quality deteriorates significantly. Agriculture is by far the biggest user and polluter of Karun water. Several large irrigation-drainage projects have been planned to bring large tracks of highly saline lands with shallow groundwater table under sugarcane production. Groundwater salinity in the region is close to that of the seawater. Two of the five projects have so far been completed but their returning drainage/salt leaching water has already contributed to a significant increase in river salinity. For the last 60 km of its route to the Persian Gulf, Karun is joined by the two Iraqi rivers of Euphrates and Tigris, thus forming a large shipping waterway over which the two countries have gone to war a number of times. Excessive use of water by Iran and Iraq has reduced the flow in the river to such extent that during the high tide seawater enters the river reaching pumping stations of Abadan and Khoramshahr. Deterioration of river water quality and the encroachment of seawater have also put the future survival of the world largest date palm plantations on the banks of this river in jeopardy. An investigation is under way to develop a long-term management plan for the reclamation and sustainable use of the Karun River. The objectives of the first phase of the project is to develop a salt interception technique for the one sugar cane plantation already in production, together with a diversion canal and appropriately located evaporation basins.