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 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 Turkey 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 Turkey; the next 27 miles (44 kilometers) sets the border between Syria and Iraq; and the remaining approximately 900 miles (1,450 kilometers) runs through Iraq. The Tigris catchment exceeds 230,839 square miles (371,500 square kilometers). From one-third to one-half of the drainage into the Tigris River originates in Turkey, 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 Turkey, 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 in 1984 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 spp.).

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

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 (Turdoides 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. At least 60 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 is causing the region to gradually dry out. As of 2021, the United Nations estimated that about 100 square miles (259 square kilometers) of farmland a year were being overtaken by the desert, forcing many of the farming villages in the area to be abandoned. 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 over-use of fertilizers and pesticides. In this case, the habitat pressures of global warming may push some species to the brink.

Bibliography

Geopolicity. Managing the Tigris-Euphrates Watershed: The Challenges Facing Iraq. Abu Dhabi, United Arab Emirates: Geopolicity, 2010.

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

Salim, Mustafa. “From Cradle to Grave.” Washington Post, 21 Oct. 2021, www.washingtonpost.com/world/interactive/2021/iraq-climate-change-tigris-euphrates/. Accessed 29 Aug. 2022.

Trondalan, Jon Martin. Climate Changes, Water Security and Possible Remedies for the Middle East. Paris, France: United Nations Educational, Scientific, and Cultural Organization (UNESCO), 2009.