MN Consultors

Have been chosen extraordinary lower reaches of the Arga and Aragon rivers as ecosystems with which to start the Iberian Riverscapes Program. It is a project that will be developed over the coming years and will aim to identify, study and promote appreciation of most sublime, unique and threatened river stages and riverine ecosystems in in our country.

Lower reaches of the Aragón River, a unique and unrepeatable landscape

Indeed, Navarra’s geography hosts one of the most original and extraordinary Iberian riverine corridors, the karst-subsidence-system of the lower reaches of Arga and Aragón rivers. It is a riverscape with a whimsical genesis that has become a dynamic and complex ecosystem as unique as threatened. The action of both rivers has transformed one of the unique sub-deserts in Europe in one of the richest and most productive alluvial floodplains in the Iberian Peninsula. This geological phenomenon of transformation has generated an original and breathtaking scenery of the riverine Iberia: La Ribera Navarra.

Figura 1. Dilution of Las Bardenas reliefs and formation of floodlains of La Ribera Navarra by the action of Aragón River.

It is located in the western extrem of 'Las Bardenas Reales' desert, a steppes-dominated sector of the Ebro valley conformed by a massive lithological karst structure of gypsum evaporites deeply deformed by dissolution and synsedimentary subsidence (Image 3 and 4). The recent –from a geological point of view- contact of the Aragón River with these reliefs (Image 8), rapidly open therethrough a fluvial valley (delimited both sides by odd fluvial cliffs) transforming the gypseous folds of sandstones, silts and marls into rich alluvial plains (Image 10). Inside the valley, topographic depressions induced by dilution and the deposition of fluvial sediment (left by the river as a consequence of its lost of energy when it reached the low-lying plain), imposed an intense morphodynamic meandering action, still active in the recent past. Cutoff processes of meanders were extremely frequent, and thus new channels were generated and old river loops abandoned (Figure 2). As a result it became a singular hidrogeographical sector with a complex metasystem of fluvial wetlands (oxbow lakes), one of the most important in the Iberian Peninsula.

Figura 2. Confluence of Arga and Aragón rivers, 1944. Intensive morphodynamic meandering action: new channels were easily generated and abandoned creating a complex system of wetlands, nowadays mostly disappeared.

Inland wetlands of fluvial origin, unknown habitats on the edge of extinction

Nowadays, sediment dredging, big dams (hydrological regime alteration and solid flow regulation) and lateral protections have simplified the river structure and induced an accelerated incision process. As a consequence, the meandering action resulted inhibited and the oxbow lakes formation process became neutralized. Moreover, most of the old oxbow lakes became artificially isolated from the main channel and are disappearing as a result of organic accretion and fluvial sediment depositions (Figure 3 and 4).

Figure 3. Diachronic study of the evolution of habitats in Soto Gil (Peralta, Navarra) after isolation of the meander from the principal axis of the river Arga conducted in 1979. The results confirm the gradual decrease in water bodies by silting.

Study and divulge of an unknown treasure

Despite this critical situation, some segments of the Aragón river still preserve riverscapes that can be consider as some of the most magnificent riverine corridors of our geography.

Moreover, pilot restoration projects focuses on incision control and naturalization of geomorphological structure and morphodynamics action are being conducted. Studies aimed to increase knowledge on the relationship between morpho-functional heterogeneity and biological diversity are being conducted as well. [Read more]

As part of its corporate commitment, MN is studing and divulging currently functioning and ecological, biological, landscape and cultural values of this ecosystem, redoubt where the best European mink (Mustela lutreola) population of Southern Europe still remains. Some studies are promoted and supported by the Government of Navarra and Gestión Ambiental de Navarra SA and also involved the Department of Hydraulic, Maritime and Environmental Engineering of the Polytechnic University of Catalonia in the context of an agreement underwritten between the University and MN Consultors ^(*).

Figure 4. Evolution of water bodies in Soto Gil between 1982 and 2014, an oxbow lake of Arga river. The observed pattern of progressive reduction of water surfaces by organic and mineral silting seems to respond to a linear model. It predicts the final disappearance of the wetland before 2025.

 

^(*) All material in this article is fully protected by copyright and are property of the Government of Navarra, Gestión Ambiental de Navarra SA and MN Consultors en Ciències de la Conservació SL. Written permission must be granted for whole or partial reprints of the images contained.

 

To cite this reference

García-Pérez, G.; Manzano Serra, M.; Pascual Garsaball, R.; Cadiach Ricomà, O.; Jaso León, C.; Telletxea Galdurotz, G.; Campión Ventura, D.; Aguilar Anton, F.; Baron Moreno, J. (2014). The Aragón riverine system. First project of the program for the study and divulgation of Iberian riverscapes. Navarra, Spain.

Retrieved from MN Consultors Website [5 Jan. 2015].

URL: http://www.mnconsultors.com/informacion-corporativa/compromiso/the-aragon-riverine-system-first-project-of-the-iberian-riverscapes-program/lang/en