Karun River

Karun River is a major river located in southwestern Iran, recognized as the country’s longest and most water-rich river. With a length of approximately 900 km, the Karun originates from the high peaks of the Zagros Mountains, particularly the Zard Kuh region (4548 m), and flows through Iran’s Khuzestan Province before joining the Arvand Rūd (Shatt al-Arab) River, which empties into the Strait of Hormuz.

Geographical and Geological Characteristics

The Karun River basin covers an area of approximately 67,500 km² and includes the provinces of Isfahan, Chaharmahal and Bakhtiari, Lorestan, Kohgiluyeh and Boyer-Ahmad, and Khuzestan. This vast geography, characterized by heterogeneous topography and climatic conditions, is a significant factor influencing the river’s flow regime.

Geologically, the Karun River is part of the Tigris-Euphrates-Karun fluvial system and constitutes an important component of the Mesopotamian foreland basin. The sediments carried by the river are poor in quartz and have formed significant sedimentary deposits shaped by the region’s arid climatic conditions.

Hydrological Characteristics

The Karun River is of great importance in Iran for controlling river floods, irrigation, and supplying drinking water. Measurements conducted at the Ahvaz hydrological station between 1954 and 2005 recorded the river’s annual:

• Maximum discharge: 6704 m³/s
• Minimum discharge: 107 m³/s
• Average discharge: 641 m³/s

In recent years, significant declines in the Karun River’s flow regime have been observed due to climate change, dam construction, population growth, and agricultural use. Statistical analyses have revealed a clear downward trend since the 2000s.

Pollution and Environmental Impacts

The Karun River faces severe water pollution problems due to intensive agriculture, industry, and urban development in its surrounding areas. Studies conducted between 2009 and 2011 detected residues of organochlorine pesticides (OCPs) in the river water. In particular:

• β-Endosulfan (28.51 µg/L) and
• pp’DDT (0.01 µg/L) were found at high concentrations.

According to World Health Organization (WHO) standards, these levels exceed ecological safety thresholds and pose a threat to aquatic life.

Ecological and Historical Significance

The Karun River holds strategic importance for the region not only hydrologically but also historically and culturally. Since ancient times, particularly during the Susiana civilization, it has been used for agriculture and transportation and played a decisive role in the development of major cities such as Ahvaz.

Moreover, the sediments transported by the river have been one of the key dynamics shaping the geological evolution of the Mesopotamian region. In this regard, the Karun is regarded as a natural system of geoarchaeological significance in scientific research.