Water, Geosciences and Sustainability in the Ebro Basin

ICID 21st European Regional Conference 2005 - 15-19 May 2005 - Frankfurt (Oder) and Slubice - Germany and Poland
Water, Geosciences and Sustainability in the Ebro Basin
The EbroAgua Working Group*
* José Albiaca, Carmen Castañeda del Alamoa, Juan de la Riva Fernándezb, Götz Ebhardtc, Maite Echeverria
Arnedob, Miguel A. García Verad, Jens Hartmannc, Matthias Hindererc, Andreas Hoppec, Teresa Lamelas Graciac, Oswald Marinonic, Irene Marzolffe, Manfred Ostrowskic, Elke Peterssonc, Johannes B. Riesf, Tilman Sauerf,
Petra Schweizer-Riesg, Manuel Seegerf, Crisanto Silvac, Asunción Soriano Jimenezb, Katy Unger Shayestehc,
Axel Winterscheidc.
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Diputación General de Aragón, Zaragoza, bUniversidad de Zaragoza, cTechnische Universität Darmstadt, dConfederación Hidrográfica del Ebro, Zaragoza, eWolfgang Goethe-Universität Frankfurt, fUniversität Trier, gUniversität Magdeburg
Addresses for correspondence: [email protected], [email protected]
The Ebro Basin and its natural constraints
Spain has a wide variety of climatic zones. They range from humid regions in the north to subhumid, semiarid
and even small arid zones in south-eastern Spain and in interior depressions (as in the Ebro Basin, e. g. Monegros area). Water demand, as in some areas triggered seasonally by agriculture and tourism, does not coincide
with the natural occurrences. So, different strategies for irrigation and water transfer have been developed during
the last years [1, 2] generating severe social-political-technical and scientific controversies.
Figure 1. Digital elevation model of the Ebro Basin.
The Ebro River and its main tributaries are more than 12,000 km long. The whole Ebro Basin covers an area of
85,000 km2. The highest run-offs are concentrated in the Pyrenees and the Cantábrica Range. The mean annual
discharge is 18,200 million m3 (MCM). The area has a population of 2,800,000 inhabitants. The annual water
consumption is 6,000 MCM and may reach 9,000 MCM in the future. To preserve the existing Ebro delta, an
annual minimum outflow of 3,100 MCM to the sea is necessary.
The Ebro Basin is the southern foreland basin of the Pyrenees, with an asymmetrical (in its western parts a
symmetrical) fill of Tertiary sediments thickening to the north. It is bounded by the Iberian Ranges to the south
and the Catalan Coastal Ranges to the east. Both, the Pyrenees and the Iberian Ranges have produced thrust
sheets at its margins reducing mainly during the late Oligocene the basin width by about 70 %. Pre-Oligocene
successions include shelf carbonates and marls, coastal and deltaic detrital facies, and evaporites. Post-Oligocene
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ICID 21st European Regional Conference 2005 - 15-19 May 2005 - Frankfurt (Oder) and Slubice - Germany and Poland
sediments of the Ebro Basin sediments are continental and reach thicknesses of more than 1.000 m. They include
a wide variety of alluvial deposits, fresh-water lacustrine carbonates and saline playa lake deposits. The alluvial
sediments were deposited in relatively localized alluvial fans (<15 km long) as well as in larger systems up to
100 km long.
At the end of the Tertiary, the basin changed from a closed interior basin to one drained by the Ebro River to
the Mediterranean Sea. The respective incision and sedimentation of the river dominates the present geomorphology. Quaternary deposits, like pediments and fluvial terraces commonly crowned by calcretes, cover about
one-third of the depression. Subsurface dissolution of evaporates caused local thickening in some places [3].
The EbroAgua Working Group and its questions
The EbroAgua Working Group consist of Spanish and German scientists from the University of Zaragoza, from
authorities of the Region of Aragón and the Ebro River Basin Authority (Confederación Hidrográfica del Ebro),
and from the Darmstadt University of Technology with partners at the universities of Frankfurt am Main, Trier
and Magdeburg. It will concentrate its investigations on the Central Ebro Basin in the Region of Aragón.
Although sustainability is a term frequently used in debates on the future of society and its needs (e. g. European Water Frame Directive), many questions seem to be open with respect to a sustainable management of the
Ebro River system. For instance, its geology is well known, but more data are still necessary to reconstruct the
geologic “architecture” of the area in order to answer questions on its natural resources and hazards involved
with the use of these resources. Such questions are e. g.:
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How much groundwater is available and what is its quality?
What is the value of thickened alluvial deposits as rich sources of aggregates needed for construction in
urban areas and what is its value as groundwater reservoirs?
Is it possible to elaborate risk maps with respect to subrosion of Tertiary evaporites which may result in
sagging as well as collapse features? How will changes in land use or irrigation techniques applied in agriculture effect erosion?
What will be the amount of sediment trapped in the water reservoirs that were originally mobilised by
erosion on agricultural areas?
How will possible changes in climate affect present water management and the water management provisioned in the National Hydrological Plan?
What will be the economic impacts?
Is it possible to elaborate a dynamic geographic information system which will allow the modelling of
different land use scenarios?
How are the ongoing water related projects accepted by the local population and what could improve or
decrease the acceptance?
As it can be seen easily, the current working group concentrates on geologic and economic questions as well as
on water management. However, the EbroAgua Working Group is open for other scientists with other questions.
Those who want to know more about the group and its current activities may refer to
http://www.unizar.es/EbroAguaWorkingGroup/
References and data sources
[1] Confederación Hidrográfica del Ebro (1996), Plan hidrológico de la cuenca del Ebro, disponible en www.chebro.es
[2] Ministerio de Medioambiente, Secretaría de Aguas y Costas, Dirección General de Obras Hidráulicas y calidad de las aguas (2000), Libro
Blanco del Agua en España.
[3] W. Gibbons & T. Moreno, eds (2002): The Geology of Spain, Geol. Soc. London.
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ICID 21st European Regional Conference 2005 - 15-19 May 2005 - Frankfurt (Oder) and Slubice - Germany and Poland
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