Tagus River e-Flows: a tool for integrated water management, Spain



Demosite Location
Demosite Location


Demosite Location

Information about lithology/geochemistry:

The Tagus River is the longest river in the Iberian Peninsula. This international river flows westward from the headwaters in central Spain to its estuary in Lisbon (Portugal), dividing the Iberian Plateau into north and south. Madrid and Lisbon, the Spanish and Portuguese capital cities, are in its basin (Figure 1). More than 10 million people live in the catchment —most of them (more than six million) in the Madrid region, in the upper catchment, which implies serious pollution problems for the middle Tagus River.

Main Description

  • The river catchment is the scale of water management in the European Union. As the Tagus River is a transboundary river, its management competences are divided into two parts: the Spanish and the Portuguese demarcation. Ecological flows are presented as an Ecohydrology measure that must be implemented in all surface water bodies in the basin to achieve an improvement in the ecological status of the whole.

Conserve Ecohydrological processes in natural ecosystem


Enhance ecohydrological processes in novel ecosystem


Apply complementary Ecohydrological processes in high impacted system


This table presents the different categories of ecosystem services that ecosystem can provide, divided in:

Provisioning Services are ecosystem services that describe the material or energy outputs from ecosystems. They include food, water and other resources.
Regulating Services are the services that ecosystems provide by acting as regulators eg. regulating the quality of air and soil or by providing flood and disease control.
Ecosystem services "that are necessary for the production of all other ecosystem services". These include services such as nutrient recycling, primary production and soil formation.
Cultural Services corresponds nonmaterial benefits people obtain from ecosystems through spiritual enrichment, cognitive development, reflection, recreation, and aesthetic experiences.

EH Principles

Quantification of the hydrological processes at catchment scale and mapping the impacts

Ecological engineering (integration, dual regulation and biotechnologies in catchment scale for enhancement of ecological potential)


Areas of the floodplain have been transformed into lagoons or shallow swamps covered with emergent macrophytes (Thypha angustigolia, Phsgmytes australis) that function as lagoon systems that purify discharges of organic matter and nutrients.


E-Flows should provide habitat through ecological and geomorphological processes, but also should offer a temporal pattern of flows that allows seasonal changes in composition and structure as in the reference communities. In order to achieve these objectives, e-Flows must have the following components: ● Minimum flows that must be exceeded in order to conserve aquatic communities ● Maximum flows that must not be exceeded in order to protect native species adapted to Mediterranean summer low flo

Hydrological Flow

In order to enhance the effects of environmental flows in the aquatic and riverside communities, modifications have been made to the existing infrastructures in the river: a) Elimination or lowering of transversal barriers to increase longitudinal connectivity and reduce the surface of the impounded river. b) Elimination or setback of longitudinal dikes that manage to increase transversal connectivity, providing more space during floods where processes associated with riparian vegetation encroachment, aquifer recharge, soil enrichment and nutrient capture are carried out.

Ecohydrological Infrastructure

Major Issues

Social ecohydrological system

EH Objectives

Cultural Heritage

EH Methodology

Catchment Ecohydrological sub-system


  • There is a rich, long traditional river culture around the Tagus linked to the riverine populations, but this cultural heritage is severely threatened due to the loss of traditional activities linked to the Tagus and, also, due to the loss in the ecological status of the river. For example, the transformation of river vegetation, the pollution of water and the decrease in water flows have progressively moved the local population away from the Tagus riverine areas for traditional activities such as bathing, walking or enjoying nature.

  • The Tagus River has outstanding natural and cultural values, as well as important problems, including excess of water abstractions, urban and agricultural water pollution, alteration of water flows, degradation and transformation of river banks and presence of many barriers. However, these values and problems of the Tagus are not well known by a significant part of the local populations.

  • The present Tagus river-basin management plan and its specific set of rules, as well as other legislation pieces regarding ecological flows and water uses constitutes a framework that present limitations that should be addressed in future legislative changes. However, the present legislative framework offers room for a substantial improvement in the actual implementation of policies and practices. In this demosite, opportunities within the present legislation to promote the proposed ecohydrology approach will be identified and applied as levers for change. The approval of the hydrological plans for the Tagus basin in Spain has not been without problems in terms of both procedural and content issues.

  • The Tagus river-basin management plan formally intends to apply an integrated water policy, taking into account the environmental objectives as well as the economic and societal water uses. However, it presents water policies that are not being successful for the effective recovery of the Tagus River. This demosite will provide practical examples on how alternative water policies, particularly regarding the management of water flows, can be implemented with little impact on water uses while, at the same time, substantially improve the biodiversity, the water quality and the landscape and nature values of the river.

  • The conventional water management in the Tagus river-basin (and in general in Spain) has paid little or no attention at all to water governance issues. In fact, the engagement of stakeholders and an active participation of the population are still scarcely considered in present management. This lack of attention to the perceptions, needs and suggestions of citizens constitutes an important barrier to implement innovative policies, as the one outlined in the proposed ecohydrology approach.

  • Stakeholders

  • Cátedra del Tajo UCLM-Soliss (Universidad de Castilla-La Mancha, UCLM)

  • Grupo Hidrobiología (Universidad Politécnica de Madrid, UPM)

  • Grupo Agua, Clima y Medio Ambiente (Universidad de Alcalá, UAH)

  • Confederación Hidrográfica del Tajo (Pending reply to the letter of request for collaboration)

  • Fundación Nueva Cultura del Agua (FNCA)

  • Red Ciudadana por una Nueva Cultura del Agua en el río Tajo/Tejo y sus ríos

  • Plataforma de Toledo en defensa del Tajo

  • Plataforma en Defensa de los ríos Tajo y Alberche de Talavera de la Reina

  • Asamblea de Aranjuez en defensa del Tajo

  • Jarama Vivo


  • Plataforma en defensa de los ríos de Madrid

  • Fundación Soliss

  • Suntory Beverage and Food Spain (Pending sending the letter of request for collaboration)

  • Catchment Sociological sub-system


    • The following activities have been taken place:

    • -Monitoring instream daily flows along River Tajo and its main tributaries

    • -Monitoring nutrients and water quality along River Tajo and its main tributaries

    • -Monitoring the biological status (macroinvertebrates, fish and algae) along the River Tajo

    • -Analysis of the environmental flows assigned to each section of the Tagus River and evaluation of the degree of compliance each year.

    • -Identification of occurring flow-biota interactions at R. Tajo, and assessment of which of them are acting as limiting factors for the achievement of good ecological status. We will focus on those factors that depend on the circulating flows, since their analysis will allow the improvement in the design of their environmental flows.

    • -Investigation of other factors that may be conditioning the ecological state of the Tagus River (nutrients, water quality or geomorphology), in cases where flow-biota interaction (dual regulation) is not found. In the case of factors associated with water quality, verify dilution issues

    • and in the case of geomorphological factors, evaluate the physical restoration of the channel.

    • -Previous activities have provided the scientific background for the development and design of problem-solving methodology for the improvement in the design of their environmental flows, the mitigation of the eutrophication and pollution problems, and the restoration of the geomorphic processes.

    Expected Outcomes

    • The Hydrological Plan approved in 2023 is very ambitious in that it aims to achieve the good status of all water masses by 2027. To this end, it has implemented numerous measures to improve water quality, river restoration, as well as advances in the establishment of ecological flows.

    Latest Results


    Beatriz Larraz

    • beatriz.Larraz@uclm.es
    • Catedra del Tajo UCLM-Soliss (Universidad de Castilla-La Mancha, Spain)


    No democard yet.


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