Ebro

Name

The Greeks called the river Ἴβηρ (Ibēr), abir, ah'ir and the Romans called it the Hibēr, Ibēr, or Ibērus flūmen, leading to its current name. The Iberian Peninsula and the Hibērī or Ibērī (the people of the area) were named after the river. It is not known with any certainty whether the Greeks used a local native name for the river, nor is it known what the words hibēr or ibēr might have meant. In modern Basque the word ibar means 'valley' or 'watered meadow', while ibai means 'river', but it is unknown whether these words are related to the etymology of the Ebro River. There are rivers in the Balkans called Ibar (Montenegro and Serbia) and Evros (Bulgaria and Greece). The Greek name might have referred to the Jewish colonies along the river and around the area, as the Hebrew word for a Hebrew-speaking Jew or Hebrew-speaking colony is Ivrí or Ivērí.

History

In antiquity, the Ebro was used as the dividing line between Roman (north) and Carthaginian (south) expansions after the First Punic War (264–241 BC). When the Roman Republic, fearful of Hannibal's growing influence in the Iberian Peninsula, made the city of Saguntum (considerably south of the Ebro) a protectorate of Rome, Hannibal viewed the treaty violation as an aggressive action by Rome and used the event as the catalyst to the Second Punic War.

One of the earliest Cistercian monasteries in Spain, Real Monasterio de Nuestra Señora de Rueda (lit. 'Royal' Monastery of Our Lady of the Wheel), is located on the banks of the Ebro in Aragon. Established in 1202, the edifice survives intact. The monastery is strongly connected to the Ebro, since it used one of the first large waterwheels built for the production of power in Spain. The monastery also diverted flow from the Ebro to create a circulating, hydrological central heating system for its buildings.

The Ebro in 1938 was the starting ground of one of the most famous Republican offensives of the Spanish Civil War. Known as the Battle of the Ebro, the offensive ended in defeat for the Republican forces, although they enjoyed success in its first stages. They were not able to reach their objective of Gandesa.

Flow and floods

The Ebro is the most important river in Spain in terms of length, 928 km (577 mi), and area of drainage basin, 85,550 km² (33,030 mi²). However, the mean annual flow decreased by approximately 29 percent during the 20th century due to many causes: the construction of dams, the increasing demands for irrigation and the evaporation (higher than the rainfall, due to low rainfall, high sunshine and strong and dry winds) from reservoirs in the river basins. This situation has a direct impact on the deltaic system at the mouth of the river because its hydrological dynamics are mainly controlled by the river discharge.

The decrease in river discharge has meant introduction of the salt wedge further into the river. The mean annual river flow is approximately the critical flow which determines the formation and the break-up of the salt wedge. Thus, when the river discharge is between 300 and 400 m³/s (11,000 and 14,000 cu ft/s), the salt wedge can occupy the last 5 km (3 mi) of the estuary, but when the discharge is between 100 and 300 m³/s (3,500 and 10,600 cu ft/s), the salt wedge can advance up to 18 km (11 mi) from the mouth. For less than 100 m³/s (3,500 cu ft/s), the salt wedge quickly advances to its maximum extent, reaching 32 km (20 mi) from the mouth. In addition to decreased mean annual flow, the increased river regulation in the Ebro basin has produced daily and seasonal changes in the flow pattern.

With regards to the sediment load, several authors conclude that the sediment load was reduced by more than 99 percent during the last century. The drastic reduction in sediment transport implies a sediment deficit in the delta, which is causing the erosion of the coastline and lack of sediment replenishment. The unstable surface is due to weather changes and tidal surges. The river floods from time to time, although advance warning can now be given as a result of monitoring within the catchment area. The river flow in Zaragoza during floods, from the end of the 19th century is as follows:

• March 1888: 3,760 m³/s (132,800 cu ft/s)
• January 1891: 3,250 m³/s (114,800 cu ft/s)
• February 1892: 3,790 m³/s (133,800 cu ft/s)
• January 1895: 3,118 m³/s (110,100 cu ft/s)
• March 1930: 3,600 m³/s (127,100 cu ft/s)
• December 1930: 3,000 m³/s (105,900 cu ft/s)
• October 1937: 3,000 m³/s (105,900 cu ft/s)
• January 1941: 4,000 m³/s (141,300 cu ft/s)
• February 1952: 3,260 m³/s (115,100 cu ft/s)
• January 1961: 4,130 m³/s (145,800 cu ft/s)
• November 1966: 3,154 m³/s (111,400 cu ft/s)
• January 1981: 2,940 m³/s (103,800 cu ft/s)
• February 2003: 2,988 m³/s (105,500 cu ft/s)
• March 2003: 2,220 m³/s (78,400 cu ft/s)
• April 2007: 2,282 m³/s (80,600 cu ft/s)

The Ebro poured 1,874 million cubic metres (1,519,000 acre-feet) into the delta from 27 March 2007 to 11 April 2007, with an average of 117 million cubic metres (95,000 acre-feet) per day.

Ecology

Academics and local government have criticised ecological impacts of:

• dams
• pollution from populations
• factories
• agricultural dumping
• invasive species affecting the original ecosystem; the introduced species have rapidly caused the extinction of numerous indigenous species

In past times numerous lagoons, endorheic saltwater ponds, and freshwater swamps and marshes were drained, dried or filled. Almost entire riparian forests were cleared for crops or for pulpwood forest plantations. Due to these changes numerous plant and animal species have disappeared. Due to dams and hydraulic canalization, the dynamics of the river have been altered and new scroll-bars, new oxbow lakes, and new abandoned meanders will not now be created. Over a period of time, many of these phenomena tend to dry out or fill in with sediments. Some small representatives of these river dynamics and wetlands are protected.

The Ebro Delta Natural Park, covering 7,802 hectares (19,280 acres), was finalised in 1986 and is of international importance for 8 of its plant species and 69 of its vertebrate fauna. It has some 95 breeding species of birds, is also very important for a wide range of overwintering species, and serves as an essential stopover point for large numbers of migratory birds. The Ebro delta has the world's largest colony of Audouin's gulls. In 2006 it held a record number of more than 15,000 pairs, its highest to date.

The introduction of American crayfish Procambarus clarkii has resulted in economic losses, introduced elsewhere for cultivation, its success is attributable to its ability to colonise disturbed habitats that would deter the edible iberian crayfish. The semiaquatic rodent Myocastor coypus is beginning to expand in some northwest tributaries of the head damaging crops and protected national parks in the Basque Country. Fish caught in all lower reaches of the Ebro are high in mercury and the European Union prohibits their sale, notably the huge Wels catfish.

The zebra mussel, an invasive species, is expanding upstream in the Ebro's waters. Due to its rapid rate of reproduction, the species adversely affects the port's underwater machinery as well as that of dams and hydroelectric plants, in addition to competing with native species. Following the introduction of Wels catfish, many fish species' numbers are in clear and rapid decline. Since the Wels catfish's introduction in the Mequinenza reservoir in 1974, it has spread to other parts of the Ebro and its tributaries, especially the Segre. Some endemics species of iberian barbels, genus Barbus in the Cyprinidae, have declined drastically, having once been abundant, especially in the Ebro. Competition and predation by Wels catfish caused its complete disappearance in the middle channel Ebro around 1990. Barbel species from mountain stream tributaries of the Ebro that Wels catfish have not colonized were not affected. The ecology of the river also now has the problem of a major increase in aquatic vegetation, seaweed and algae.

Notes and citations

Explanatory footnotes