The Ebro (Spanish and Basque ; , , ) is a river of the north and northeast of the

Iberian Peninsula The Iberian Peninsula ( ), also known as Iberia, is a peninsula in south-western Europe. Mostly separated from the rest of the European landmass by the Pyrenees, it includes the territories of peninsular Spain and Continental Portugal, comprisin ...

, in

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

. It rises in

Cantabria Cantabria (, ; ) is an autonomous community and Provinces of Spain, province in northern Spain with Santander, Cantabria, Santander as its capital city. It is called a , a Nationalities and regions of Spain, historic community, in its current ...

and flows , almost entirely in an east-southeast direction. It flows into the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

, forming a

delta Delta commonly refers to: * Delta (letter) (Δ or δ), the fourth letter of the Greek alphabet * D (NATO phonetic alphabet: "Delta"), the fourth letter in the Latin alphabet * River delta, at a river mouth * Delta Air Lines, a major US carrier ...

in the

Terres de l'Ebre Terres de l'Ebre (, in English 'Ebro, Ebre Lands') is the south-westernmost of the eight regions (Vegueria, ''vegueries'') defined by the Regional Plan of Catalonia. It has a population of 182,231 as of 2022, placing it second to last in terms of ...

region, in southern

Catalonia Catalonia is an autonomous community of Spain, designated as a ''nationalities and regions of Spain, nationality'' by its Statute of Autonomy of Catalonia of 2006, Statute of Autonomy. Most of its territory (except the Val d'Aran) is situate ...

. In the Iberian peninsula, it ranks second in length after the

Tagus The Tagus ( ; ; ) is the longest river in the Iberian Peninsula. The river rises in the Montes Universales between Cuenca and Teruel, in mid-eastern Spain, flows , generally westward, and empties into the Atlantic Ocean in Lisbon. Name T ...

and second in discharge volume, and

drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...

, after the

Douro The Douro (, , , ; ; ) is the largest river of the Iberian Peninsula by discharge. It rises near Duruelo de la Sierra in the Spanish Soria Province, province of Soria, meanders briefly south, then flows generally west through the northern par ...

. It is the longest river entirely within Spain; the other two mentioned flow into

Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...

. The Ebro flows through many cities ():

Reinosa Reinosa is a municipality in Cantabria, Spain. , it has 10,307 inhabitants. The municipality, one of the smallest by land area in Cantabria, is notable for being one of the nearest towns to the headwaters of the Ebro River. It is surrounded by th ...

; Frías and Miranda de Ebro in

Castile and León Castile and León is an Autonomous communities of Spain, autonomous community in northwestern Spain. Castile and León is the largest autonomous community in Spain by area, covering 94,222 km2. It is, however, sparsely populated, with a pop ...

; Haro,

Logroño Logroño ( , , ) is the capital of the autonomous community of La Rioja (Spain), La Rioja, Spain. Located in the north of the Iberian Peninsula, primarily in the right (South) bank of the Ebro River, Logroño has historically been a place of pa ...

, Calahorra, and Alfaro in

La Rioja La Rioja () is an autonomous communities in Spain, autonomous community and provinces of Spain, province in Spain, in the north of the Iberian Peninsula. Its capital is Logroño. Other List of municipalities in La Rioja, cities and towns in the ...

; Tudela in

Navarre Navarre ( ; ; ), officially the Chartered Community of Navarre, is a landlocked foral autonomous community and province in northern Spain, bordering the Basque Autonomous Community, La Rioja, and Aragon in Spain and New Aquitaine in France. ...

; Alagón, Utebo, and

Zaragoza Zaragoza (), traditionally known in English as Saragossa ( ), is the capital city of the province of Zaragoza and of the autonomous communities of Spain, autonomous community of Aragon, Spain. It lies by the Ebro river and its tributaries, the ...

Aragon Aragon ( , ; Spanish and ; ) is an autonomous communities of Spain, autonomous community in Spain, coextensive with the medieval Kingdom of Aragon. In northeastern Spain, the Aragonese autonomous community comprises three provinces of Spain, ...

; and Flix,

Móra d'Ebre Móra d'Ebre () is the capital of the ''comarca'' of the Ribera d'Ebre in Catalonia, Spain. It is situated on the right bank of the Ebre river in the Móra Hollow, and is served by the N-420 road to Reus and Gandesa, the N-230 road to Lleida ...

, Benifallet, Tivenys, Xerta, Aldover,

Tortosa Tortosa (, ) is the capital of the '' comarca'' of Baix Ebre, in Catalonia, Spain. Tortosa is located at above sea level, by the Ebro river, protected on its northern side by the mountains of the Cardó Massif, of which Buinaca, one of the hi ...

, and

Amposta Amposta () is the capital of the ''comarca'' of Montsià, in the province of Tarragona, Catalonia, Spain, 190 km south of Barcelona on the Mediterranean Coast. It is located at 8 metres above sea level Mean sea level (MSL, often shorten ...

in the

province of Tarragona Tarragona (; ) is a province of eastern Spain, in the southern part of the autonomous community of Catalonia. It is bordered by the provinces of Castellón, Teruel, Zaragoza, Lleida and Barcelona and by the Mediterranean Sea. The province's po ...

(

Geography

Upper part and tributaries

The source of the river Ebro is in the Cantabrian Mountains, in Fontibre,

(''Fontibre'' is from Latin , i.e. 'source of the Ebro'), just from the

Bay of Biscay The Bay of Biscay ( ) is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Point Penmarc'h to the Spanish border, and along the northern coast of Spain, extending westward ...

, in the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

. Close by is a large

artificial lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

, ''Embalse del Ebro'', created by its damming. The upper Ebro rushes through rocky gorges in Burgos Province. Flowing roughly eastwards it passes and begins forming a wider river valley among

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

rocks when it reaches

and

. Southern tributaries rise on the nearby watershed, the Sistema Ibérico, a mountain range among those of Spain's centre. North of the headwaters is the Cantabrian mountain range (south of

Bilbao Bilbao is a city in northern Spain, the largest city in the Provinces of Spain, province of Biscay and in the Basque Country (greater region), Basque Country as a whole. It is also the largest city proper in northern Spain. Bilbao is the List o ...

and Santander). Much of the total water volume of the Ebro comes from its northern tributaries, which drain about of the southern slopes of the

Pyrenees The Pyrenees are a mountain range straddling the border of France and Spain. They extend nearly from their union with the Cantabrian Mountains to Cap de Creus on the Mediterranean coast, reaching a maximum elevation of at the peak of Aneto. ...

mountains, which run along the border with

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

. All of Andorra's drainage basin is in the Ebro, through the Segre.

Climate

Downstream from Cantabria the climate in the Ebro basin – the valley being isolated from sea air masses by surrounding mountains – becomes Mediterranean/Atlantic influenced and

continental Continental may refer to: Places * Continental, Arizona, a small community in Pima County, Arizona, US * Continental, Ohio, a small town in Putnam County, US Arts and entertainment * ''Continental'' (album), an album by Saint Etienne * Continen ...

. This implies summer/winter seasonal contrast and a rather dry climate. Summers of the Ebro Valley most often mirror those of a

semiarid climate A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of se ...

; some of them see more breaks of storms or showers, yet others are more

arid Aridity is the condition of geographical regions which make up approximately 43% of total global available land area, characterized by low annual precipitation, increased temperatures, and limited water availability.Perez-Aguilar, L. Y., Plata ...

, bringing

drought A drought is a period of drier-than-normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, ...

save where advanced irrigation is used. The valley

flood plain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...

s experience annual

rainfall Rain is a form of precipitation where water droplets that have condensed from atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. ...

between , with maxima in fall and spring. It is often covered with

chaparral Chaparral ( ) is a shrubland plant plant community, community found primarily in California, southern Oregon, and northern Baja California. It is shaped by a Mediterranean climate (mild wet winters and hot dry summers) and infrequent, high-intens ...

vegetation. Summers are hot and winters are cold. The dry summer season has temperatures of more than , occasionally reaching over . In winter, the temperatures often drop below . In some areas the vegetation depends heavily on moisture produced by condensation fog. It is a continental Mediterranean climate with extreme temperatures. There are many ground frosts on clear nights, and sporadic

snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...

falls.

Soil and geology

The natural

topsoil Topsoil is the upper layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs. Description Topsoil is composed of mineral particles and organic mat ...

s across the plains are, outside of historically well-forested zones, thin. The subsoil being close to the surface is organically poor and quick-draining: calcareous, pebbly, stony layers. These are in places salt-rich, seeing some saltwater

endorheic An endorheic basin ( ; also endoreic basin and endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water (e.g. rivers and oceans); instead, the water drainage flows into permanent ...

lagoons.

Karst Karst () is a topography formed from the dissolution of soluble carbonate rocks such as limestone and Dolomite (rock), dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. Ther ...

geological processes shaped the landscape of layers of soluble

carbonate rock Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO3), and Dolomite (rock), dolomite rock (also kn ...

of extensive limestone

bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of bed ...

formed in an ancient seabed.

Flow volume

The valley expands and the Ebro's flow then becomes slower as its water volume increases, flowing across Aragon. There, larger tributaries flowing from the central Pyrenees and the Iberian System discharge large amounts of water, especially in spring during the thawing season of the mountain snow.

Ecosystems

The

biome A biome () is a distinct geographical region with specific climate, vegetation, and animal life. It consists of a biological community that has formed in response to its physical environment and regional climate. In 1935, Tansley added the ...

s are diverse in these Mediterranean climate zones:

Mediterranean forests, woodlands, and scrub Mediterranean forests, woodlands and scrub is a biome defined by the World Wide Fund for Nature. The biome is generally characterized by dry summers and rainy winters, although in some areas rainfall may be uniform. Summers are typically hot in ...

. Hinterlands are particularly distinctive on account of extensive

sclerophyll Sclerophyll is a type of vegetation that is adapted to long periods of dryness and heat. The plants feature hard leaves, short Internode (botany), internodes (the distance between leaves along the stem) and leaf orientation which is parallel or ...

shrublands known as maquis, or garrigues. The dominant species are ''

Quercus coccifera ''Quercus coccifera'', the kermes oak or commonly known as Palestine oak, is an oak shrub or tree in section '' Ilex'' of the genus. It has many synonyms, including ''Quercus calliprinos''. It is native to the Mediterranean region and Northern ...

'' (in drier areas) and '' Quercus ilex''. These trees form monospecific communities or communities integrated with ''

Pinus A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as c ...

'', Mediterranean

buckthorn ''Rhamnus'' is a genus of about 140 accepted species of shrubs or small trees, commonly known as buckthorns, in the family Rhamnaceae. Its species range from tall (rarely to ) and are native mainly in east Asia and North America, but found thr ...

s, '' Myrtus'', '' Chamaerops humilis'',

juniper Junipers are coniferous trees and shrubs in the genus ''Juniperus'' ( ) of the cypress family Cupressaceae. Depending on the taxonomy, between 50 and 67 species of junipers are widely distributed throughout the Northern Hemisphere as far south ...

s, '' Pistacia'', '' Rosmarinus'', ''

Thymus The thymus (: thymuses or thymi) is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. The thymus ...

'', and so on. The hinterland climate becomes progressively more continental and drier, and therefore there is an end from extreme temperatures accompanied by slow-growing dwarf juniper species to unvegetated desert steppes as in "llanos de Belchite" or "Calanda desert". The mountain vegetation is mostly coniferous forests that are drought-adapted, and hardier trees in the oak genus (''

Quercus An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

''), typically less tolerant, in the wetter highlands.

Halophile A halophile (from the Greek word for 'salt-loving') is an extremophile that thrives in high salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more ...

s (

extremophile An extremophile () is an organism that is able to live (or in some cases thrive) in extreme environments, i.e., environments with conditions approaching or stretching the limits of what known life can adapt to, such as extreme temperature, press ...

s as to salt) abound in zones of endorheic lagoons and their feeder creeks.

Tamarix The genus ''Tamarix'' (tamarisk, salt cedar, taray) is composed of about 50–60 species of flowering plants in the family Tamaricaceae, native to drier areas of Eurasia and Africa. The generic name originated in Latin and may refer to the Ta ...

-covered, these include endemic species of

bryophyte Bryophytes () are a group of embryophyte, land plants (embryophytes), sometimes treated as a taxonomic Division (taxonomy), division referred to as Bryophyta ''Sensu#Common qualifiers, sensu lato'', that contains three groups of non-vascular pla ...

s, chenopodiaceae,

plumbaginaceae Plumbaginaceae is a family (biology), family of flowering plants, with a cosmopolitan distribution. The family is sometimes referred to as the leadwort family or the plumbago family. Most species in this family are perennial plant, perennial h ...

, ruppiaceaes, ''

Carex ''Carex'' is a vast genus of over 2,000 species of grass-like plants in the family (biology), family Cyperaceae, commonly known as sedges (or seg, in older books). Other members of the family Cyperaceae are also called sedges, however those of ge ...

'', lythraceaes, asteraceaes, and others. Their presence is related to the marine origin of the valley and the extensive marine deposits. Just as it enters Catalonia, the valley narrows, and the river becomes constrained by mountain ranges, making wide bends. 3 massive dams have been built in this area: Mequinenza dam ( Province of Zaragoza, 1955), Riba-roja dam (1955), and Flix dam (1948), the latter two in the

. In the final section of its course the river bends southwards and flows through spectacular gorges. The calcareous cliffs and high, rocky hills of the Serra de Cardó almost abut the river separating the Mediterranean coastal strip. After passing the gorges, the Ebro bends again eastwards near

before discharging in a

on the Mediterranean Sea close to

in the province of

Tarragona Tarragona (, ; ) is a coastal city and municipality in Catalonia (Spain). It is the capital and largest town of Tarragonès county, the Camp de Tarragona region and the province of Tarragona. Geographically, it is located on the Costa Daurada ar ...

The delta

The Ebro Delta (), in the

('Ebro Lands') region,

, is at , or 20km² less, one of the largest

wetland A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...

s of the western Mediterranean. Designated a

Ramsar site A Ramsar site is a wetland site designated to be of international importance under the Ramsar Convention,8 ha (O) *** Permanent 8 ha (P) *** Seasonal Intermittent < 8 ha(Ts) **

. Recorded and thus confirmed as a

seaport A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as Hamburg, Manc ...

in the Roman Warm Period in the 4th century, it is now well inland from the mouths. The rounded form of the delta attests to the subsequent balance between

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

deposition by the Ebro and removal of this material by wave

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

. The modern delta is in intensive

agricultural Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created f ...

use for rice, fruit (in particular citrus), and vegetables. The Ebro delta also has numerous beaches, marshes, and salt pans that provide habitat for over 300 species of birds. The Ebro delta was classified as a wetland area of international interest by Spain's Bureau Mar in 1962. Since a phased-introduction law (1983 to 1986) Spain has designated as the Ebro Delta Natural Park () to protect its natural resources. A network of canals and irrigation ditches dug by agricultural and conservation groups help to maintain the ecologic and economic resources of the delta.

Name

The Greeks called the river (''Ibēr''), ''abir'', ''ah'ir'' and the Romans called it the ''Hibēr'', ''Ibēr'', or ''Ibērus flūmen'', leading to its current name. The

and the ''Hibērī'' or ''Ibērī'' (the people of the area) were named after the river.Westrem, Scott D. ''The Hereford Map: A Transcription and Translation of the Legends With Commentary'', page 328. Brepols, 2001. It is not known with any certainty whether the Greeks used a local native name for the river. Nor is it known what the word "''Ibēr''" or "''Hibēr''" might mean. In modern

Basque Basque may refer to: * Basques, an ethnic group of Spain and France * Basque language, their language Places * Basque Country (greater region), the homeland of the Basque people with parts in both Spain and France * Basque Country (autonomous co ...

the word ''ibar'' means 'valley' or 'watered meadow', while ''ibai'' means 'river', but there is no proof relating the etymology of the Ebro River with these Basque words. There are rivers in the Balkans called Ibar (Montenegro and Serbia) and Evros (Bulgaria and Greece).

History

In antiquity, the Ebro was used as the dividing line between Roman (north) and Carthaginian (south) expansions after the

First Punic War The First Punic War (264–241 BC) was the first of three wars fought between Rome and Carthage, the two main powers of the western Mediterranean in the early 3rd century BC. For 23 years, in the longest continuous conflict and grea ...

(264–241 BC). When the

Roman Republic The Roman Republic ( ) was the era of Ancient Rome, classical Roman civilisation beginning with Overthrow of the Roman monarchy, the overthrow of the Roman Kingdom (traditionally dated to 509 BC) and ending in 27 BC with the establis ...

, fearful of

Hannibal Hannibal (; ; 247 – between 183 and 181 BC) was a Punic people, Carthaginian general and statesman who commanded the forces of Ancient Carthage, Carthage in their battle against the Roman Republic during the Second Punic War. Hannibal's fat ...

's growing influence in the Iberian Peninsula, made the city of

Saguntum Sagunto () is a municipality of Spain, located in the province of Valencia, Valencian Community. It belongs to the modern fertile '' comarca'' of Camp de Morvedre. It is located approximately north of the city of Valencia, close to the Costa ...

(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 The Second Punic War (218 to 201 BC) was the second of Punic Wars, three wars fought between Ancient Carthage, Carthage and Roman Republic, Rome, the two main powers of the western Mediterranean Basin, Mediterranean in the 3rd century BC. For ...

. One of the earliest

Cistercian The Cistercians (), officially the Order of Cistercians (, abbreviated as OCist or SOCist), are a Catholic religious order of monks and nuns that branched off from the Benedictines and follow the Rule of Saint Benedict, as well as the contri ...

monasteries A monastery is a building or complex of buildings comprising the domestic quarters and workplaces of monastics, monks or nuns, whether living in communities or alone ( hermits). A monastery generally includes a place reserved for prayer which m ...

in Spain, Real Monasterio de Nuestra Señora de Rueda ( Monastery of Our Lady of the Wheel), is located on the banks of the Ebro in

. Established in 1202, the edifice survives intact. The monastery is strongly connected to the Ebro, since it used one of the first large

waterwheel A water wheel is a machine for converting the kinetic energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a large wheel (usually constructed from wood or metal), with numerous blade ...

s 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 The Spanish Civil War () was a military conflict fought from 1936 to 1939 between the Republican faction (Spanish Civil War), Republicans and the Nationalist faction (Spanish Civil War), Nationalists. Republicans were loyal to the Left-wing p ...

. Known as the

Battle of the Ebro The Battle of the Ebro (, ) was the longest and largest battle of the Spanish Civil War and the greatest, in terms of manpower, logistics and material ever fought on Spanish soil. It took place between July and November 1938, with fighting mainly ...

, 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, , and area of drainage basin, . 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 Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

and the evaporation (higher than the rainfall, due to low rainfall, high sunshine and strong and dry winds) from

reservoirs A reservoir (; ) is an enlarged lake behind a dam, usually built to store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of water, interrup ...

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 , the salt wedge can occupy the last of the estuary, but when the discharge is between , the salt wedge can advance up to from the mouth. For less than , the salt wedge quickly advances to its maximum extent, reaching 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 Sediment transport is the movement of solid particles (sediment), typically due to a combination of gravity acting on the sediment, and the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural systems wh ...

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

during floods, from the end of the 19th century is as follows: * March 1888: * January 1891: * February 1892: * January 1895: * March 1930: * December 1930: * October 1937: * January 1941: * February 1952: * January 1961: * November 1966: * January 1981: * February 2003: * March 2003: * April 2007: The Ebro poured into the delta from 27 March 2007 to 11 April 2007, with an average of per day.

Ecology

Academics and local government have criticised ecological impacts of: * dams * pollution from populations * factories * agricultural dumping *

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

affecting the original

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

; the introduced species have rapidly caused the

extinction Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

of numerous indigenous species In past times numerous

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...

s, endorheic saltwater

pond A pond is a small, still, land-based body of water formed by pooling inside a depression (geology), depression, either naturally or artificiality, artificially. A pond is smaller than a lake and there are no official criteria distinguishing ...

s, and freshwater

swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...

s and

marsh In ecology, a marsh is a wetland that is dominated by herbaceous plants rather than by woody plants.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p More in genera ...

es were drained, dried or filled. Almost entire

riparian forest A riparian forest or riparian woodland is a forested or wooded area of land adjacent to a body of water such as a river, stream, pond, lake, marshland, estuary, canal, Sink (geography), sink, or reservoir. Due to the broad nature of the definitio ...

s were cleared for crops or for

pulpwood Pulpwood can be defined as timber that is ground and processed into a fibrous pulp. It is a versatile natural resource commonly used for Papermaking, paper-making but also made into low-grade wood and used for chips, energy, pellets, and engineered ...

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 lake An oxbow lake is a U-shaped lake or stream pool, pool that forms when a wide meander of a river is meander cutoff, cut off, creating a free-standing body of water. The word "oxbow" can also refer to a U-shaped bend in a river or stream, whether ...

s, and new abandoned

meander A meander is one of a series of regular sinuous curves in the Channel (geography), channel of a river or other watercourse. It is produced as a watercourse erosion, erodes the sediments of an outer, concave bank (cut bank, cut bank or river cl ...

s 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

s are protected. The Ebro Delta Natural Park, covering , 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 The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...

prohibits their sale, notably the huge Wels catfish. The

zebra mussel The zebra mussel (''Dreissena polymorpha'') is a small freshwater mussel, an Aquatic animal, aquatic bivalve mollusk in the family Dreissenidae. The species originates from the lakes of southern Russia and Ukraine, but has been accidentally Intro ...

, an

, 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 In fish anatomy and turtle anatomy, a barbel is a slender, whisker like sensory organ near the mouth (sometimes called whiskers or tendrils). Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the z ...

, genus '' Barbus'' in the

Cyprinidae Cyprinidae is a family of freshwater fish commonly called the carp or minnow family, including the carps, the true minnows, and their relatives the barbs and barbels, among others. Cyprinidae is the largest and most diverse fish family, and t ...

, 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

Citations

External links

*
The River Ebro and Delta

The Ebro Delta at Google Maps

* ttp://www.flordeldelta.com/data_en/sal-gourmet.php The Trinidad Salt Pans within the Ebro River Delta Nature Reserve
Awarded "EDEN – European Destinations of Excellence" non traditional tourist destination 2009

in the ''

Columbia Encyclopedia The ''Columbia Encyclopedia'' is a one-volume encyclopedia produced by Columbia University Press and, in the last edition, sold by the Gale Group. First published in 1935, and continuing its relationship with Columbia University Columbi ...

'' {{Authority control * European drainage basins of the Mediterranean Sea Rivers of Aragon Rivers of Burgos Rivers of Cantabria Rivers of Castile and León Rivers of Catalonia Rivers of La Rioja (Spain) Rivers of Navarre Rivers of Spain