The Tagus River

The Tagus River flowing through Lisbon, Portugal at night, shortly before emptying into the Atlantic Ocean.
The Tagus River flowing through Lisbon, Portugal at night, shortly before emptying into the Atlantic Ocean.

5. Description

The longest river of the Iberian Peninsula, the 1,038-kilometer long Tagus River arises in the Sierra de Albarracín of eastern Spain and flows westward across Spain past Teruel, Meseta, and Toledo to form parts of the Spanish-Portuguese border. The Tagus then enters into Portugal, flowing southwest until it drains into the Atlantic Ocean not far from Lisbon. The Tagus River drains an area of 80,100 square kilometers along its course, and forms an estuary of economic significance at its mouth near Lisbon. Most of the major tributaries join the Tagus on its right-hand banks, and the Alagón and Jarama Rivers are two of its chief tributaries.

4. Historical Role

The Tagus River, being one of the major rivers of the Iberian Peninsula, played a crucial role throughout history in encouraging the growth of settlements in the region. For centuries, the river has served as a lifeline for the people settled in its watershed, and thus was also instrumental in the development of the Spanish and Portuguese empires. In 1606, the Nossa Senhora dos Mártires, or the Pepper Wreck, saw a cargo ship wrecked at the mouth of the river near Lisbon when it struck a rock near the shore and sank. Until 2008, it remained the only Portuguese Indiaman ship known to be damaged, not by treasure hunters or pirates, but by a true sea accident. The Targus River, because of its significance in the lives of the Spanish and Portuguese, has also often been mentioned in many songs, poetry, and writings by the people of the Iberian Peninsula.

3. Modern Significance

The estuary of the Tagus River serves as one of the finest harbors in all of Europe, and hosts one of the continent’s longest suspension bridges, the Ponte 25 de Abril, which is 3,323 feet long. A very small section of the river, in its lower portion, is navigable, while most of the course of the river passes through deep gorges interrupted by waterfalls. Dams and hydroelectric power stations are common on the Tagus and, by the 1980s, 60 dams existed on the river, with an installed power capacity of more than 1,200,000 kilowatts. The dams serve the dual purpose of providing water for irrigating the agricultural lands along the river basin as well as generating electricity for the settlements living near the river. Cereal farming and the growth of olive trees and vineyards are important agricultural activities near the river basin. The coniferous forests in the upper course of the river support a thriving timber industry.

2. Habitat and Biodiversity

The climate throughout the basin of the Tagus River is of a semi-arid nature in its upper and middle reaches while towards the estuary, an oceanic climate prevails. Coniferous forests of pine and oak grow in the upper reaches of the river basin though about one third of the land of this basin has been cleared for agriculture. Royal carp, black bass, trout, and barbels are some of fishes caught in the Tagus and its reservoirs. Mammalian species like the Pyrenean ibex and fallow deer, and avian fauna like sand grouses, wall creepers, and raptors, might be spotted along the river's basin.The wetland ecosystems near the estuary of the Tagus Reserve are protected as the Tagus Estuary Natural Reserve due to its high ecological significance. Several species of migratory birds, including the Pied avocet, Greater flamingo, Dunlin, Grey-lag goose, Blue-throat, Little egret, Black-winged kite, and Booted eagle, can be observed in this region. Besides birds, the estuary is also highly rich in its diversity of insect and fish species.

1. Environmental Threats and Territorial Disputes

Pollution and damming are two of the major threats to the Tagus River and its wild habitats. The Tagus River provides drinking water to the millions of people settled along its banks, but this resource is under the risk of being heavily polluted as waters from industrial and municipal point sources have often dumped their wastes into the waters of the river. Extensive damming of the river also impacts the natural flows of the river, which in turn increases the chances of the erosion of its banks in the lower courses of the river, and also adversely affects the migration of fish species along the river.


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