GUADIANA RIVER: HISTORY, MOUTH, ROUTE, CHARACTERISTICS - GEOGRAPHY - 2024

The Guadiana River is a Spanish-Portuguese watercourse located in the Iberian Peninsula, specifically in the Southern Plateau. It runs approximately 852 km between Spain and Portugal and its waters move in a general direction from east to west, serving in two sections as a border between these countries.

Its length makes it worth the fourth place among the longest rivers on the peninsula. Its basin covers 67,733 km² of which 82% correspond to Spain and the remaining 18% are in Portugal.

The Guadiana basin covers 67,733 km². Photo: Francisco Antunes

Human intervention on its riverbed with the construction of dams and reservoirs has had a double effect: on the one hand, there are the specialists who affirm that the basin is overexploited and, on the other, the environmentalists who defend the wetlands and the wildlife that they congratulate the administration of water resources for the generation of new habitats.

History

Augusta Emerita Foundation

One of the most important archaeological antecedents of human settlements in the Guadiana River is located on the current Spanish city of Mérida, capital of the Autonomous Community of Extremadura.

The second longest Roman bridge in the entire empire is located on this site over the Guadiana riverbed, with 792 meters in length and 60 arches. This bridge served as the entrance to the Roman city of Augusta Emerita.

The foundation of the city is estimated in the year 25 a. C. as a residence for retired soldiers, being a reward for their services to the empire. In the various episodes of conquest and reconquest of the territory, the bridge has been blown up to prevent the entry of enemy troops into the city. The bridge has scars that show its restoration in the 17th and 19th centuries.

War of succession

In 1709, during the War of Succession, Spanish forces demolished part of the Ajuda Bridge, located to the southwest of the current Autonomous Community of Extremadura that linked the Portuguese Olivenza with the rest of Portugal, saving the Guadiana River.

This action was carried out to prevent Olivenza from becoming an outpost for Portugal in a possible attempt to seize territory from Spain during the instability generated as a result of the struggle for the succession to the crown.

After the signing of some treaties, Spain assumed de facto sovereignty over Olivenza, integrating it into its territory. The question about this sovereignty still generates controversy in certain circles of Portuguese society.

Napoleonic era

In 1811, within the framework of the Napoleonic wars, the Guadiana River served as the scene of various battles between French troops and the Spanish-Portuguese coalition.

On February 19, 1811, a contingent of Spain and French forces faced each other in the Battle of Gévora in the municipality of Bajadoz in the Autonomous Community of Extremadura.

The French found some fords and crossed the Guadiana, taking the Spaniards by surprise, who, confused, fled in disarray. This attack produced one of the most disastrous defeats of the war for the Spanish side.

The French army took the city of Badajoz after the Spanish defeat and defended it until June 17, 1811 when they withdrew to other positions and the Anglo-Portuguese occupied the city.

Source and mouth

The biggest dispute about the Guadiana River is generated around its birthplace. In this regard, there are three hypotheses that place it in different places.

On the one hand there are those that locate its source in the Ruidera Lagoons located in the Autonomous Community of Castilla-La Mancha, in Spain. These are made up of a set of 15 consecutive lagoons separated by jumps of up to 24 meters high. This section is known as the Guadiana Alto or Guadiana Viejo river and runs superficially for a space of 76 km to the Mill of Membrillera.

At this point, the river flow disappears due to the joint action of the permeable terrain formed by limestone deposits and evaporation, to reappear 26 km later to the west in Ojos de Guadiana, in the municipality of Villarrubia de los Ojos (Ciudad Real).

The second hypothesis places its source in the Ojos de Guadiana at the confluence of the Gigüela and Záncara rivers.

The third version affirms that the Guadiana river is born in the Fuente del Ojuelo, in the Campo de Montiel located above the Lagunas de Ruidera to the north of the town of Viveros (Castilla-La Mancha).

Travel

The Guadiana River runs approximately 852 km of Spanish and Portuguese territory. In Spain it bathes part of the territory of Castilla-La Mancha, passing to Extremadura and then Andalusia. In Portugal it touches the districts of Portalegre crossing towards Évora, then Beja and finally its mouth in Faro.

Its current is divided into four parts: Guadiana Viejo, high course, middle course and low course.

Old Guadiana

This section includes from its “birth”, whether it is located in the Fuente del Ojuelo or in the Lagunas de Ruidera, passing through its disappearance in the Molino de la Membrillera. At this point, the waters of the Old Guadiana are integrated into an underground natural reservoir known as Aquifer 23 to emerge at the end of this section through the Ojos de Guadiana spring.

High course

It goes from the Ojos de Guadiana spring bathing the municipality of Ciudad Real and the municipality of Puebla de Don Rodrigo, to the Cíjara reservoir on the border between the Autonomous Community of Castilla-La Mancha and the province of Badajoz.

Middle course

It is located between the Cíjara reservoir to the city of Bajadoz. Here it extends through the province of Bajadoz, passes through the municipalities Villarta de los Montes and Helechosa de los Montes, then enters the La Serena-Vegas Altas Comprehensive Services Association and from there to the municipalities of San Pedro de Mérida, Villagonzalo, Don Álvaro and the city of Mérida. Touch different locations to finally reach the city of Bajadoz.

Low course

Here the Guadiana river passes into the territory of Portugal. The lower course runs from the city of Bajadoz to its mouth in the Atlantic Ocean. It goes through the district of Portalegre passing to the district of Évora, forming the border between Spain and Portugal.

At this point it strictly enters Portuguese territory through the town of Juromenha and from there to the Alqueva reservoir in Alentejo. Upon overcoming the dam, it passes to the Beja district, touching the cities of Serpa and Mértola, to resume its border function after Pomarão.

The last important populations before joining the Atlantic Ocean, forming the border between the Spanish province of Huelva and the Portuguese Faro District, are Sanlúcar de Guadiana and Ayamonte on the Spanish side and Foz de Odeleite and Vila Real de Santo Antonio on the Portuguese side.

Tributaries

The Guadiana River receives water from multiple surface and underground sources along its course, the most important being the Caya, Vascao, Frío, Cadavais, Foupana, Bullaque, Valdehornos, Odeleite, Chocas, Cigüela, Estena, Beliche, Záncara rivers. Guadarranque, Jabalón, Ruecas, Zújar, Alcollarín, Guadalupe, Gévora, Guadámez, Ardila, Búrdalo, Chanza, Matachel and Tirteafuera.

Threats to its channel

Starting in 1970, conservationists began to warn about the excessive use of the groundwater that feeds the Guadiana River for agricultural purposes. The abuse of this water source became evident around 1983 when the springs of the Ojos de Guadiana dried up.

This situation lasted 30 years until 2012, when some disconnected lagoons appeared in the plain, which formerly flooded the springs. This was due to the effect of an excessively humid weather period that occurred between 2009 and 2013.

In the spring of 2013, the water finally resumed its surface course, helped by a Spanish government project that consisted of the installation of a mill to artificially extract underground water and feed the surface course.

In January 2017, the surface flow had not recovered its autonomy, this scenario has been extended until 2019 with the request of the Guadiana Hydrographic Confederation, aimed at the inhabitants of the upper basin who are in a pre-alert state, requiring that they the emergency plans for the management of water resources are in place.

Long periods of drought have caused the average flow of the river to decline more and more, directly affecting agriculture and tourism that depend on water for their development. This endangers the subsistence and way of life of the entire region.

characteristics

The Guadiana River has unique characteristics derived from the geological composition of its basin and human intervention on it.

Strategic water reserve

Throughout its course, the governments of Spain and Portugal have taken advantage of the Guadiana flow for its use in favor of the agricultural and social development of the regions it bathes.

In order to make more efficient use of water, a set of dams and reservoirs have been built with two fundamental purposes: firstly, to have water reserves to meet the needs of the population and crops in dry periods; and in second place for power generation.

Hydroelectric potential

Among these constructions, the Alqueva Reservoir stands out, which has a surface area of ​​250 km ² and 1,100 km of shore, which makes it the largest reservoir in Europe.

It is located in Portuguese territory and with its waters serves an approximate 100,000 hectares of Spanish-Portuguese land dedicated to agricultural use. The dam has two hydroelectric plants with an installed capacity of 520 megawatts per hour.

tourism

Together with their strategic value for the administration of water resources and the generation of hydroelectric energy, the reservoir lake and the Alqueva dam are a great tourist attraction visited by more than 2,000 people every week, taking into account only the statistics of the beaches Portuguese. At the lake you can enjoy water activities and tourist facilities ideal for family visits.

Contamination

Renowned international environmental organizations such as Greenpeace affirm that the state of contamination of the Guadiana is alarming and worsens as it passes through the main cities.

The quality of the water in this river is affected by the agricultural activities carried out on its banks, the discharge of industrial and urban wastewater with poor or no treatment, and the proliferation of dams and reservoirs.

Intensive agricultural activities on the banks of the river lead to its waters polyphosphate, which hinders the oxygenation of the water and affects the flora and fauna that depend on the river.

The discharge of industrial and urban wastewater carries nitrogen and phosphorus into the river, which decomposes organic matter and accelerates the eutrophication processes. The Spanish Ministry of the Environment denounced that many municipalities that discharge their waters into the Guadiana do not have treatment plants or use outdated technology that does not work properly.

The reservoirs and dams stop the water, reducing the regenerative and self-regulatory capacity of the river. As a consequence, the decomposition processes initiated by oxygen loss and eutrophication are accelerated.

Flora

The Guadiana River flows through the Southern Plateau of the Iberian Peninsula in a relief dominated by plains. It supports aquatic and emergent vegetation as well as rupicolous vegetation and tree species, all of which depend to a greater or lesser extent on soil moisture filtered mainly from the river and from underground sources.

On the banks of the Guadiana there are honeysuckle, willows, lily, poplar, broom, ash, brambles, alder, buttercups, tarajes, ash trees, hawthorn, churreros reeds, reeds, cattails, elm, holm oaks, hawthorn, cork oaks, rose hip, pine forests, lagoon grass, meadows, nettle and wild roses.

Fauna

The fauna has protected areas because they serve as a refuge for a large number of species. The Guadiana River Azud deserves special mention, located in the city of Badajoz, which in 2004 was declared a Special Protection Area for Birds. With an extension of 17 km, this dam or weir floods 400 hectares, ideal for bird watching in their natural environment without having to leave the city.

In the area you can see: Bittern, Cattle Egret, Rail, Purple Heron, Thrush, Little Egret, Sapper Plane, Squacco Heron, Kingfisher, different species of ducks, orioles, white storks, nightingales, common finches, robins and herons real.

The freshwater clam, river shrimp, American crab, otter, eel, barbel, Guadiana boga, calandino, carp, goby, pike, tench and rainbow trout are also appreciated in some areas of its channel.

References

1. The Guadiana dies: this is how a plant in the Amazon devours the fourth river of Spain, El Español digital newspaper, published on December 11, 2017, taken from elespanol.com.
2. José Ramón Aragón, The underground waters of the upper basin of the Guadiana river and the framework directive, Conference on the Present and future of groundwater in Spain and the European Framework Directive. Zaragoza, 2002. Taken from ftp://ftp.oph.chebro.es
3. Mariano Velazco, 100 years in the development of the upper basin of the Guadiana River, Doctoral Thesis National University of Distance Education, year 2003, taken from e-spacio.uned.es.
4. Decree "Hydrological Plan 2010-2015", Guadiana Hydrographic Confederation, taken from planhidrologico2009.chguadiana.es.
5. Rodríguez, Manuel, Las Tablas de Daimiel and the Ojos del Guadiana geology and piezometric evolution, Technology and Development Magazine Nº. 2, 2004, taken from researchgate.net.