Tigris River

• Category: Inland Aquatic Biomes.
• Geographic Location: Asia.
• Summary: Long a fertile provider to natural species and human cities alike, the Tigris River has been damaged, and many of its diverse habitats have been disrupted.

The Tigris River bounds Mesopotamia from the east; the Euphrates River sets the western boundary. The name Mesopotamia, or between the rivers, speaks to the great fertile lands between these great flows that gave rise to many ancient civilizations.

The Tigris originates in the Taurus Mountains of eastern Türkiye and flows southward through Iraq, passing through Baghdad, and joins the Euphrates near the southern Iraqi marshlands, then flows through the Shatt al-Arab estuary to drain into the northern reaches of the Persian Gulf.

From its origin in tiny Lake Hazar to the gulf, the Tigris is about 1,180 miles (1,900 kilometers). About 248 miles (400 kilometers) of its length runs through Türkiye; the next 27 miles (44 kilometers) flows through Syria; and the remaining approximately 900 miles (1,450 kilometers) runs through Iraq. The Tigris catchment is about 145,000 square miles (375,000 square kilometers). From one-third to one-half of the drainage into the Tigris River originates in Türkiye, with other source water streaming down from the Zagros Mountains of Iran.

The Tigris system experiences major spring flooding, which has been in recent times heavily controlled by the erection of dams in Türkiye, Iran, and Iraq. These controls, added by the mid-20th century, have dramatically changed the hydrology of lower Mesopotamia, especially the dynamics in the southern marshes and alluvial plains. Large dams mark a fundamental departure in the course and focus of the basin’s historical riverine development. They induced a major shift from ancient downstream diversion activities by barrages and irrigation canals in the lowlands of southern Iraq in ancient times to modern water storage and hydroelectric projects in the upper basin of the Tigris and its associated tributaries.

As the Tigris flows southward beyond the headwaters, it nears the third-largest city in Iraq, Mosul, where the largest dam in Iraq was constructed and completed by the mid-1980s to provide hydroelectric power.

Flora and Fauna

The range of aquatic plants in the Tigris includes submerged varieties such as pondweed (Potamogeton lucens) and eelgrass (Vallisneria sp.), emergent types such as reed mace (Typha domingensis), and the iconic papyrus (Cyperus papyrus).

Water lilies, duckweed, hornwort, and stonewort are also found in abundance, interspersed with broad swaths of common reed (Phragmites australis).

In the southern reaches of the Tigris, and particularly around the marshlands north of the Shatt al-Arab estuary, many stands of date palm (Phoenix dactylifera) have been grown, both naturally and by cultivation, since antiquity.

Among Tigris River animals that are endemic, or found nowhere else on Earth, two are birds: the Iraq babbler (Argya altirostris) and the Basra reed warbler (Acrocephalus griseldis). Both find sanctuary among the reeds and ponds of the southern marshlands, which serve as a vital stopover for millions of birds migrating between the three continents of Africa, Asia, and Europe. Among them are pelicans, cormorants, gulls, herons, ducks, and storks.

The marshes are also a vast nursery for shrimp, mollusks, and fish that are key to the ecosystem here and to the economic livelihood of many Iraqis. Numerous species of fish dwell in the Tigris River biome, including the endemic catfish Glyptothorax steindachneri. The Hilsa shad (Tenualosa ilisha) is anadromous, spawning in the waters of the estuary, the marshes, or the Tigris proper and growing to maturity in the Persian Gulf or the greater Indian Ocean to which it is linked.

Threats

Climate change is exerting an irrepressible rise in temperatures across the Tigris River region, bringing great stress to many habitats. The rising temperatures and decreased rainfall are causing the region to gradually dry out. In 2023, the United Nations estimated that, in Iraq, about 400,000 acres of farmland a year were being overtaken by the desert owing to degradation, forcing people to abandon many of the farming villages in the area. The 2020 and 2021 rainy seasons were the driest in 40 years across the country, which led to a 29 percent decrease in water flow in the Tigris and a 73 percent decrease in the Euphrates. However, numerous species here have evolved in a climate regime that has seen many cycles of drought and flood across the millennia. Still, the current warming occurs against a background marked by unprecedented human-driven impact: construction, damming, water diversion and drain-offs, air pollution, tainted water, war and its dislocations, poaching, ill-considered land-use, and agricultural overuse of fertilizers and pesticides. In this case, the habitat pressures of global warming may push some species to the brink. The Mesopotamian marshes in Iraq are declining critically, negatively affecting the biodiversity and habitats of the region.

Bibliography

“Climate Change Costs Iraq 400,000 Dunums of Agricultural Land Annually: UN.” Rudaw, 14 Aug. 2023, www.rudaw.net/english/middleeast/iraq/140820231. Accessed 4 Mar. 2026.

Geopolicity. Managing the Tigris-Euphrates Watershed: The Challenges Facing Iraq. Geopolicity, 2010.

Hamden, M. A., et al. Vegetation Response to Re-Flooding in the Mesopotamian Wetlands, Southern Iraq. Society of Wetland Scientists, 2010.

“Iraq Is Losing 400,000 Acres of Agricultural Land Annually Due to Climate Change.” +964, 14 Aug. 2023, en.964media.com/1087/. Accessed 4 Mar. 2026.

McCarron, Leon. “The Tigris: The River That Birthed Civilization.” BBC, 1 Aug. 2023, www.bbc.com/travel/article/20230731-the-tigris-the-river-that-birthed-civilisation. Accessed 4 Mar. 2026.

“The Mesopotamian Marshes: A World Heritage on the Brink.” United Nations Iraq, 15 Jan. 2025, iraq.un.org/en/308406-mesopotamian-marshes-world-heritage-brink. Accessed 4 Mar. 2026.

Salim, Mustafa. “From Cradle to Grave.” The Washington Post, 21 Oct. 2021, www.washingtonpost.com/world/interactive/2021/iraq-climate-change-tigris-euphrates/. Accessed 4 Mar. 2026.

Trondalen, Jon Martin. Climate Changes, Water Security and Possible Remedies for the Middle East. United Nations Educational, Scientific, and Cultural Organization, 2009.