The Odiel River

How is your watershed (1)  

The course of the river Odiel river runs entirely in the province of Huelva with a global NS since birth in the Sierra de Aracena, 600 m altitude, until it flows through the estuary of Huelva in the Ocean Atlantic. It has a total length of 128 km and an average slope of 0.56%. The Odiel River watershed drains a total area of 2,310 km 2 being the major sub basin of the Odiel river itself, which forms the main sub-basin, river and Rivera Olivargas Mecca. The most important tributaries of the Odiel receives on its right bank and are Olivargas River River Rivera Oraque and Makkah. The Odiel river network is a network embedded in the bedrock and alluvial deposits barely. The river bed is generally rocky and very shallow.

Odiel river Basin (Source: (1))

The Sierra de Aracena is the highest point (900 m) in the NN E Basin, from there down to the coastal shelf in Huelva. In terms of relief, you can consider the area as a tilted toward the south, where the highest levels in the N-NW are the Sierra de San Cristóbal (701 m) and the Vaca Peña (644 m) peneplain.

Odiel River at a point near San Plato mine, its stony bed is observed and very shallow (Source: Amaya)


Climatological features of the basin are characteristic of Mediterranean climate with hot dry summers and mild winters. A north-south gradient is recognized from continental Mediterranean climate in the area of his birth and high course, to Mediterranean ocean in its lower reaches and mouth. There is a marked seasonal climate variability, especially in regard to rainfall, since rainfall is usually concentrated in the months of November to March, which contrasts with the dryness that occurs in the summer. A strong interannual scale rainfall variability is also recognized, with years of abundant rainfall alternating with extremely dry years.

The potential environmental climatophilous Odiel river vegetation (up Gibraleón, where the river loses its fluvial character), corresponds to the series and thermomediterranean mesomediterranean the oak (Quercus rotundifolia) on ombrotype dry sub-humid and siliceous materials (source Amaya)


The Odiel river crosses three geologically distinct sections which determine both their physical and hydrochemical characteristics. His birth belongs to the South-Portuguese Zone Hercynian Iberian Massif, where it intersects high-grade metamorphic rocks and Cambrian age. After this and during the high middle and passes the FPI . In its lower reaches the Odiel crosses Tertiary materials and developed alluvial Quaternary deposits in transition to marsh. Of all the materials traversed by the Odiel, is passing through the FPI and its interaction with the mining areas the fact that more and more negative influence has to water quality and ecosystem of the river. The stratigraphic record of the FPI consists of Paleozoic materials and includes a Vulcano-Sedimentary Complex with acidic and basic volcanic rocks between two powerful clastic units: the PQ group consisting of slate and quartzite, and Culm flyschoide group formed by a series of shales and greywackes. The geology of the basement greatly influence the hydrogeology of the area, while in the north the predominantly impermeable nature of the rocks that form the substrate prevent the existence of aquifers under the river bed sediments of the Miocene Betic allow Trench some infiltration and movement of groundwater.

 

  Three examples of typical rocks of the FPI, from left to right boards (PQ group), dacite (CVS) and quartzite (Culm facies) (source: Amaya)


Most of the existing soils in the watershed are genuine type formed on bedrock by climatic alteration thereof. So, geology prints its main features, highlighting stoniness and shallowness, the result of erosion resistance of the starting material and irregular and heavy precipitation trailing much of the topsoil. They belong to the type of lithosols and are in the upper and middle part of the province. His underdeveloped largely limited capacity to retain rainwater reaching saturation soon, sparking an intense surface runoff which is reflected in a surge in the flow of rivers.

Typical Floor Odiel river basin, with stony and shallow (source: UHU)


The hydrological regime is characterized by marked temporal irregularity, both within the same hydrological year, with extended summer periods when the rivers and streams are practically dry, and most of the rainfall is concentrated in a few weeks of the year, and between years consecutive hydrological. The mean monthly minimum flow range from June to September and a peak from December to March. Registered for each month, year to year, values ​​can vary significantly.

  Flood of the Odiel river bridge in the A-478, between the towns of Calanas Zalamea and the Real; despite floods occasionally occur throughout the year, may transport a large part of the Annual toxic load. (Source: panoramio.com and Amaya)


The character of the Odiel river is lost in Gibraleón, from where it creates a complex estuary where the Odiel Marshes Nature Reserve, declared in 1983 a Biosphere Reserve under the MAB Programme of UNESCO, which is of great importance is placed Ecological being a Site of Community Interest (Habitats Directive 92/43/EEC) and a Special Protection Area for birds (SPA) according to Directive 79/409/EEC.

Odiel Marshes Nature Reserve (source: Amaya)

A wounded river

The basin (2)

The river network of the Odiel river basin is degraded by acidic leachates generated in mining multiple foci scattered throughout it. This contamination affects both the three sub-basins that comprise (Oraque, Mecca and Odiel) so that 1,149 km of rivers are polluted 427 km (37% of total). The principal mines of contaminating sub Oraque are San Telmo (in its northern part) and Tharsis (in the southernmost). The latter, along with mine The Lapilla, are responsible for most of the degradation of the basin of Mecca. The main discharges that pollute the main course of the river Odiel come leachate Mining District Rio Tinto, Odiel reaching the stream through the Agrio. Other mines as Sotiel, Tinto Santa Rosa, La Torerera, Cuerva de la Mora, La Zarza, etc., Are responsible for the degradation of other rivers.

Mouth of the creek in the Odiel Agrio River, just upstream of the bridge of the Five Eyes, from here the Odiel undergoes a drastic and irreversible pollution (Source: Amaya)


In the basin of the Odiel, the courses affected not have values ​​close to neutral pH and low power (average of 262 mS / cm) conductivity, while the affected courses have acidic conditions (average of pH 3.9) and high conductivity electrical (mean 2200 S / cm). As in the Tinto, the courses affected by AMD Odiel Basin as we move away from polluting sources recovery of water quality by natural attenuation processes occurs.

Odiel River Basin, indicating the streams affected and not affected by acid mine drainage and the location of the principal mines (Source: (2))


Its main runway (3)

The ecological status of the Odiel river varies from very good or good in the head and upper reaches of the river, after a bad first contribution from mining (confluence with the Arroyo Mina Concepción). Thus, more than half of the river course (54.7%), corresponding to the average current, is in a state of very low conservation.

First contribution acid Odiel River confluence with the Arroyo Mina Concepción (source: (2))

 

Odiel River in its upper reaches, after receiving input from various mines acids (source: Amaya)


From the point where it receives the first contribution from mining to wetlands, water quality is very low due to the high acidity and metal concentrations, which greatly limits the development of aquatic life. These water features also carry a limited presence of riparian vegetation and wildlife, the latter almost nonexistent. While the river is far from population centers, farms and abandoned mining infrastructure, pose a serious disruption of the waterfront.

Middle reaches of the river Odiel before Sotiel Crowned (source: Amaya)


And yet, should not be so (3 and 4)

Despite everything said, the wealth of information that exists on this river, shows the Odiel river as a living in the past:

"He had in the past ... ... exquisite quality waters with fishing and ... clams in their sandy bottoms."

"Their margins were populated forests, orchards and gardens. There was also farmland that stretched surrounding hills. "

"In some mills dams offered his services ford Waterman. Raised freshwater fish caught with net millers in aliviaderas of hurt. "

This good condition observed in the upper reaches of the river before receiving the first contribution from mining, where water quality is excellent, and although it receives a discharge, are minor and quickly autodepuran; indicators also Organic is also found in a high state of preservation, in regards to both wildlife as aquatic and riparian vegetation.

Upper reaches of the river Odiel, before receiving acidic inputs, good condition (source: panoramio.com) observed

In fact, everything must change (5)

The current state of the Odiel river is due to the mining of the last 150 years and there is nothing natural, since the conditions presented by the river before the nineteenth century were far enough current. Unfortunately it has been assumed that the natural state of the river is the current and, therefore, no need to take action for recovery.However, and although in some areas the magnitude of the problem is large, if they bet on economic treatments like acid soil recovery by amendment with limestone products or treatments liabilities AMD , as described in this LIFE -ETAD, you can advance quite in environmental recovery Odiel river.

Recovery of acid soils by using limestone products conducted by CMA and Amaya Poderosa mine, the acid drainage from mining that directly lead to the Odiel river (source: Amaya)

In this sense, the implementation of the Water Framework Directive, which requires to achieve good ecological status of all aquatic ecosystems at European level, should be a strong impetus to the work of restoring this river so mistreated along the history.

 

 

(1) Aduvire, O., Barettino, D., López-Pamo, E., Sánchez, J. Santofimia, D. 2003. Estudio de los Drenajes Ácidos de Minas y su Tratamiento Mediante Sistemas Pasivos en la Cuenca del Río Odiel (Faja Pirítica, Huelva). Instituto Geológico y Minero de España, Ministerio de Ciencia y Tecnología, Madrid, España
 
(2) Miguel-Sarmiento, A., Nieto-Líñán, J.M., Olías-Álvarez, M., Ruiz-Cánovas, C. 2010. La Contaminación Minera de los Ríos Tinto y Odiel. Disponible en: Juanta de Andalucia

(3) Alonso, M., Bellobí, M., Caño, F., Comas, E., Granero, J., Moral, I. et al. 2002. Actuaciones preliminares correctoras de la calidad ecológica integral de los ríos Tinto, Odiel y Piedras, Volumen IV. Informe de síntesis del río Odiel. Comisaría de Aguas, Confederación Hidrográfica del Guadiana, Ministerio de Medio Ambiente, Madrid, España

(4) Gómez-Ruiz, R. 2003. Los Molinos del Río Odiel. Disponible en: 
Junta de Andalucía.

(5) Europa Press. 2013. El estado actual del Tinto y Odiel se debe a la minería de los últimos 150 años y "no tiene nada de natural". Disponible en: 
Europa Press 
Prueba de mapa de imágenes sacyr uhu uhu

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