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There is a mounting body of literature dealing generally with the dynamics of transitions of human systems towards sustainability and specifically with the different stages and processes of transitions. However, the question of why transition processes occur in the first place remains largely unexplained. This paper explores the concept of transition triggers, such as culture or material resource scarcity, and provides a theoretical framework to explain the emergence of a transition and its relation to recent developments in Spanish water policy. We adapt the general framework provided by current transition theory and gather empirical evidence and insights from processes occurring within the Spanish policy context and the Ebro river basin in particular. Our results show that the sole existence of biophysical limits to water use or development cannot explain the start of a possible sustainability transition in this domain in Spain. Changes in the existing water policies in the direction of sustainability were not ignited by people directly affected by water scarcities but by a coalition of sensitive agents, mostly from academia, NGOs and local constituencies, who managed to articulate new identities, integrate multiple sources of policy relevant knowledge, and develop new values under the umbrella of the new water culture movement. [ABSTRACT FROM AUTHOR]

Nowadays, the detection of areas with high nitrate concentration in groundwater is of public concern because an excess of these nitrogen compounds in any area represents serious environmental pollution. Hence, governmental agencies require geostatistical researchers to develop methods for assessing nitrate concentration. In this paper, we propose a linear mixed model which incorporates both spatial as well as longitudinal information with the particular objective of detecting areas with excess of nitrate in groundwater. The model extends in a natural way the traditional kriging approach, incorporating the longitudinal dimension. We illustrate the results using real data taken from wells pouring into the Ebro river and its tributaries in the province of Navarra, Spain. [ABSTRACT FROM AUTHOR]

Background, Aim and Scope. Past and present management of the Ebro catchment have altered water sediment and nutrient fluxes of the lower Ebro River and its delta. The constructidn of the Mequinensa and Riba-Roja dams during the 1960s disrupted the sediment transport continuity. As a result, the lower Ebro River and its delta are facing a reduction in sediment delyery which is estimated to be up to 99% of its original yield (about 3 × 107 t/yr). Consequently, about 45% of the emerged delta will be under the mean sea level by 2100 due to subsidence and sea level rise, whereas the delta coast is retreating at a rate of several meters per year in the mouth area. This paper aims to establish the basis for a sediment management plan directed to offset the effects of the sediment delivery deficit of the Ebro delta. Main Features. A new management plan named ‘Integrated Plan for the Protection of the Ebro Delta’ (PIPDE) is being presently elaborated in order to develop sustainable management of the Ebro River and delta through an integrated management of water, sediment and habitats, in order to achieve European Union (EU) Water Framework Directive (WFD) requirements. Among other aspects, the plan aims to restore the sediment flux of the lower Ebro River by means of both the removal of the sediment trapped behind the dams and the transport of the sediment down-stream of the reservoirs to the river mouth and delta plain. Results. Preliminary studies show that the ‘flushing flood’ method has lower costs and is the most adapted method to transfer the sediments retained into the Riba-Roja dam. The required sediment load to stop coastal retreat in the mouth area and to compensate relative sea level rise represents 10 times the present suspended load (0.021 g/l), but is 10 times lower than the total volume of sediment delivered to the sea under natural conditions. Sediment delivery to the delta plain can be accomplished through the rice irrigation system, a method used prior to dam construction. Discussion. Problems of achieving a sustainable management of water and sediment are mostly linked to reservoir management. Technical problems associated with by-passing sediments through the reservoirs can be solved through operational and structural changes. Benefits of sediment flow recovery are multiple, including maintenance of the reservoir capacity, possible decline of invasive species, reduction of elevation loss and coastal retreat in the delta. Conclusions. The partial restoration of sediment fluxes in the lower Ebro River and its delta is technically feasible and environmentally desirable, but further detailed studies need to be carried out before the plan can be implemented. Perspectives. Overall, the sustainability of the lower Ebro River and delta can only be guaranteed by the implementation of a new reservoir management concept where the ecological and morphological values, as well as the economical and social values, have to be taken into consideration. [ABSTRACT FROM AUTHOR]

This work proposes a new statistical modelling approach to forecast the hourly river level at a gauging station, under potential flood risk situations and over a medium-term prediction horizon (around three days). For that aim we introduce a new model, the switching regression model with ARMA errors, which takes into account the serial correlation structure of the hourly level series, and the changing time delay between them. A whole modelling approach is developed, including a two-step estimation, which improves the medium-term prediction performance of the model, and uncertainty measures of the predictions. The proposed model not only provides predictions for longer periods than other statistical models, but also helps to understand the physics of the river, by characterizing the relationship between the river level in a gauging station and its influential factors. This approach is applied to forecast the Ebro River level at Zaragoza (Spain), using as input the series at Tudela. The approach has shown to be useful and the resulting model provides satisfactory hourly predictions, which can be fast and easily updated, together with their confidence intervals. The fitted model outperforms the predictions from other statistical and numerical models, specially in long prediction horizons. [ABSTRACT FROM AUTHOR]

Juveniles of Solea solea were sampled during the spring season in three consecutive years at a marine site by the mouth of the Ebre river. The aim was to assess if the extractive works from the toxic load upstream the river could be reflected on the health status of the fish living at the immediate sea. The biomarkers selected for the in vivo field study are commonly used as indicators of chemical exposures. They include activities of energy metabolism: lactate dehydrogenase (LDH) and citrate synthase (CS); neurotoxicity: cholinesterases (ChE); xenobiotic metabolism: cytochrome P450 (CYP)-dependent: EROD and BFCOD, carboxylesterase (CbE), glutathione S-transferase (GST) and uridine diphosphate glucuronyltransferase (UDPGT); and oxidative stress parameters such as catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GPX) as well as levels of lipid peroxidation (LPO). These biomarkers were mostly analysed in liver but also in gills and muscle depending on their particular tissue distribution and role. A complementary in vitro approach was also sought to see the capacity of common emerging contaminants (pharmaceuticals and personal care products; PPCPs) to interact with the liver microsomal detoxification system of the fish (EROD, BFCOD and CbE activities). The results indicated that in fish sampled in 2015 there was an enhancement in detoxification parameters (EROD, BFCOD and gill GR), muscular ChEs and gill CS, but a decrease in CbE activity and a marked oxidative stress situation (increased LPO and decreased CAT activity). Also, 4 out of the 10 PPCPs tested in vitro were able to interact with the CYP3A4 (BFCOD) enzymatic system while the lipid regulators simvastatin and fenofibrate inhibited CbE activity, as it occurs in higher vertebrates. The in vivo results support the use of a multibiomarker approach when assessing the disturbances due to chemical exposures, not only spatially but also over time, once the influence of other variables has been taken into consideration. The in vitro results highlight the importance of the CYP3A4 and CbE pathway in pharmaceutical metabolism, also in fish. [ABSTRACT FROM AUTHOR]

Numerous wetland restoration projects have been implemented in recent years to mitigate the increasing loss of global wetland surface area caused by human activities. Most of these projects have focused on the local recovery of habitats and species diversity, with little evaluation of functional recovery. We aimed at demonstrating that constructing wetlands on a degraded floodplain increases not only the taxonomic, but also the functional diversity of macroinvertebrate assemblages by providing greater water quality to the local fauna. We studied the macroinvertebrate community using taxonomic and functional diversity indices, and the physicochemical characteristics of three wetlands constructed 5-25 years ago, and three relict natural wetlands on the floodplain of a regulated river (Ebro River, NE Spain). Constructed wetlands demonstrated significantly greater taxonomic abundance and richness of macroinvertebrates than natural wetlands. At the functional level, the richness and Shannon diversity of biological traits relating to reproduction, respiration, dispersal and feeding were also greater in constructed wetlands, which is partly explained by low inorganic nitrogen concentration in these habitats. In contrast, a high content of phosphorus and water organic matter led to the lowest values of taxonomic and functional diversity found in natural wetlands. We conclude that it is essential to consider not only taxonomic but also functional aspects at all stages of a restoration project in order to optimize its long-term efficacy to provide and support key species and functions. [ABSTRACT FROM AUTHOR]

Dreissena polymorpha (zebra mussel) is a freshwater bivalve mollusc and has been present for more than one decade in Spain. The zebra mussel causes serious ecological and socioeconomic impacts in areas where they settle. Our research aims to analyze its hydraulic habitat, developing physical models for this species, which indicates its preference and optimal microhabitat requirements. To get it, a survey was completed in a lotic reach in the lower Ebro River (Tarragona, Spain). Habitat suitability curves for the variables include water velocity, depth, Froude number, velocity/depth ratio, shear stress and shear stress ratio ( RSS). In addition, interactive effects between hydraulic parameters on habitat selection and its use were studied and bivariate habitat models were developed. A close relationship was observed between the D. polymorpha presence and mean flow velocity combined with depth, Froude number and RSS. Suitable habitat requirements for Dreissena were detected in areas with stable river beds under high flows, and velocity below 1.2 m/s with a depth of less than 5 m under regular flows. Information about zebra mussel preferences may enhance the design of monitoring programmes and the integrated control management of this invasive mussel. [ABSTRACT FROM AUTHOR]

Rivers in mediterranean climates have been extensively modified by water management infrastructure and practices, yet patterns of development and consequent effects on freshwater ecosystems have not been compared across multiple regions. To evaluate the influence of water management on mediterranean-climate rivers, we compare the historic progression of management policies, institutions, and ecosystem impacts in the Sacramento River (California, USA), Ebro River (Spain), and Biobío River (Chile) basins. There are broad similarities in patterns of ecosystem alterations related to the extensive development of dams and water management infrastructure in the three study basins. Flow regimes have been altered by the reduction of winter peak flows and increased summer baseflows. There are also common patterns of disturbance from sediment transport alteration, water quality degradation, and declines in freshwater biodiversity. Current approaches are inadequate for addressing the formidable water management challenges in California, Spain, and Chile, yet the dramatic evolution of water policies and institutions over the past 150 years suggests that further adaptation is possible. Advances toward integrated and sustainable water management models are likely to occur through incremental change, driven by growing awareness of climate change effects and public demands for water-use efficiency and improved environmental quality. [ABSTRACT FROM AUTHOR]

A deep spectral investigation of the monthly time series of Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) in 45 meteorological stations in the Ebro basin (Spain) from 1950 to 2006 for timescales ranging from 1 to 48 months was performed. In order to summarize the results for the whole basin, the spectral analysis was also carried out on the four principal components of SPI and SPEI. Results confirm that SPI and SPEI presents very similar spectral characteristics. At the shorter time scales, the signal of SPI and SPEI is characterized by purely random temporal fluctuations. The longer time scales tend to feature the signal as a smoothly varying time series or persistent, mostly due to the aggregated nature of the indices calculation. The comparative analysis of the spectral properties of the drought indices for all the 45 sites in the Ebro basin lead to the identification of global or regional effects discriminated by local effects. It was found that some periodical signals are common to almost all the sites, while others where only identified in specific meteorological stations. [ABSTRACT FROM AUTHOR]

The Flix reservoir, in the low course of the Ebro River, contains thousands of tons of polluted sediments, accumulated from the activities of a chemical factory. An ongoing project is working toward removing these pollutants. Piscivore birds like the purple heron ( Ardea purpurea) may be useful bioindicators, so eggs and nestling feathers were sampled during the 2006-2008 breeding seasons at three localities: a reference site situated upstream and two potentially affected by the toxic muds; one at the focal area and one at a distal area, the Ebro Delta. The samples were analyzed for isotopic signatures of N and C and concentrations of heavy metals and selenium. Baseline nitrogen signatures were higher in riverine sites than in the delta. Nitrogen together with carbon signatures adequately discriminated riverine and deltaic ecosystems. Mercury levels are highly influenced by the polluted sediments at Flix and pose potential risks for the birds, as they are among the highest ever recorded in heron species. Selenium and copper concentrations probably derive from other sources. Except for mercury, heavy metals and selenium levels were below toxic levels. Purple heron eggs and nestling feathers have demonstrated their usefulness as bioindicators for pollution in the river biota; feathers in particular show pollutant impacts on a strict local basis. A long series of study years is necessary in dynamic ecosystems such as this, so continued monitoring of the heron population at Flix is advisable to trace the effects of the toxic muds, particularly during their removal, because of the high levels of mercury detected. [ABSTRACT FROM AUTHOR]

In the debate over Western Europe's Middle to Upper Palaeolithic transition we need to consider the importance of both the chronology and the ecological context of the different techno-complexes, as well as the organization of production and consumption activities. In this article we study the adaptative strategies of Middle Palaeolithic human communities based on the information obtained from archaeological sites north of the river Ebro. This transition in the northern part of the peninsula presents a chronological and geographic dichotomy, with the appearance of the Upper Palaeolithic and survival of the Middle Palaeolithic. The geographic distribution appears to indicate intergroup competition and the existence of contact, albeit of an unverified nature. This competition would explain the time that elapsed before one of the cultural, and perhaps biological, groups triumphed over the other in a process culminating in the expansion of Upper Palaeolithic technology. [ABSTRACT FROM AUTHOR]

Purpose: The main aim of this work is to provide a comprehensive estimation of the sediment yield of the Ebro Basin (NE Iberian Peninsula) in the twentieth century. Materials and methods: For this purpose, we have used the reservoir sedimentation records available for a series of large dams distributed in the catchment. Records started in 1916 and ended in 2001. In addition to the sediment yield estimates, bathymetrical records permit an evaluation of spatial variations in the sediment load of the basin and the assessment of the sediment yield of the lower reaches of the river downstream of major dams. Results and discussion: Total sedimentation in the reservoirs of the basin is estimated to be in the order of 670 × 10 t. Sediment yield is five times higher in the northern catchments (Pyrenean Range, 370 t km year) than in the southern ones (Iberian Massif, 78 t km year), reflecting the particular hydromorphic conditions of these areas. Specific sediment yield (SSY) decreases with catchment area but in the southern zone is more scale-dependent. The highest SSY occurs at 350 mm year showing a decline as runoff increases. SSY of the northern zone plots high in comparison to curves found in the literature, and this is interpreted as the consequence of historical human impact on sediment delivery. The sediment load of the Ebro Basin before the widespread construction of dams and the beginning of land abandonment is estimated to be 21 × 10 t year. Conclusions: The data illustrate the distinct hydrological and geomorphic behaviour of the two hydro-climatic areas analysed in this study. The SSY data show, for instance, the lower capability of the semi-arid catchments to transfer sediment loads. SSY does not show a linear relation with runoff, a fact that corroborates general patterns previously reported in the literature. Finally, the contemporary sediment load represents around the 1% of what was potentially transported during the beginning of the twentieth century, illustrating the sedimentary deficit of the lower section of the Ebro Basin. [ABSTRACT FROM AUTHOR]

The article presents a study which examined whether habitat complexity or stability affects the feeding ecology and breeding of Eurasian otter (Lutra luta L.). The study was conducted along rivers in the Ebro River basin. The study used several parameters to characterize the diet which include the percentage of crayfish in the diet and the percentage of amphibians in the diet. Results of the study showed a narrow link between trophic diversity and stability of the freshwater ecosystems. Also cited are the changes in foraging behavior of Eurasian otter within unstable habitat.

Numerous wetlands have been created spontaneously in the Ebro river basin as a consequence of new irrigation developments over the last 50 years. Water used for irrigating farmland drains into the lower parts of small valleys to form wetlands that are mostly dominated by common reed (Phragmites australis). Bird communities established in these wetlands are still simple, partly due to the lack of management to enable their ecological functions to improve. A knowledge of which environmental features favor these bird communities is essential in order to improve the design of newly created or restored wetlands associated to future irrigation developments. For this purpose, the habitat and vegetation features of 15 wetlands have been sampled. The structure of bird communities (richness, abundance and diversity) was monitored over 3 years during the breeding season and in winter at foraging and nocturnal roosting. The presence of bushes, height of stems and distance from large wetlands (>1 ha) proved to be the most influential variables on bird community structure and on most abundant species during the breeding season. Wetland area and compactness influenced species richness and the most abundant species during winter foraging and roosting. There was a maximum stem height at which only reed-dwelling birds remained. Uncontrolled winter burning had a severe negative effect upon these recently established populations. The ecological functions of newly created or restored wetlands, including those for run-off treatment in agricultural catchments, could be substantially improved taking into account simple guidelines from these results which relate bird community characteristics to wetland features. [ABSTRACT FROM AUTHOR]

In natural systems, the chemistry of floodplain waters is a function of the source of the water, which is influenced by geomorphic features of riparian wetlands. However, anthropogenic disturbances may alter both geomorphic features and the natural balance of water mixing in the floodplain. The aim of this study was to classify riparian wetlands and characterize their water characteristics in one reach of the Middle Ebro River to assess the hydrochemical functioning of the system. In order to accomplish that goal, water samples were collected at 40 sampling sites during low-water conditions and two floods of different magnitude. Moreover, geomorphic characteristics of riparian wetlands were also analyzed to interpret the results at broader spatio-temporal scales. Three group of wetlands were identified using multivariate ordination: (1) major and secondary channels highly connected to the river by surface water, containing weakly ionized water with high nitrate levels during floods; (2) secondary channels and artificial ponds located in riparian forests near the river, most of which were affected by river seepage during the examined events. This type of sites had high major ions concentrations and elevated spatial variability with respect to nutrient concentrations during floods; (3) Siltated oxbow lakes, whose hydrogeochemical features seemed to be unaffected by factors related to river fluctuations. Total dissolved solids, major ion (sulfate, chloride, sodium, calcium, magnesium, and potassium) and nutrient (nitrate, ammonium and organic nitrogen, and phosphate) depended upon the relationships between surface and subsurface water flows. Seasonal changes and geomorphic characterization indicated that a strong functional dependence of floodplain wetlands close to the main river channel is established, whereas most of the floodplain area remains disconnected from river dynamics. Moreover, the effect of nitrate-enriched agricultural runoff seems to affect water... [ABSTRACT FROM AUTHOR]

The present study evaluated the effect of the glass eel fishery on by-catch ichthyofauna in the Ebro River delta by investigating the primary responsible factors of discard mortality, in order to assess the adequacy of fishing and sorting procedures, and assess the ecological impact of this traditional activity. Results revealed that glass eel fishery had a negative impact on by-catch ichthyofauna mainly composed of mugilid fry and small-size estuarine species. Data showed that between 10 and 69% of incidental species died as a consequence of glass eel capture and sorting procedures. Differences in by-catch fish mortality rates depended on the glass eel sorting time, the total weight of catch, the discard ratio, by-catch fish size, and by-catch fish species composition. The total weight of the catch and the discard ratio were two of the main parameters affecting discarded fish mortality, since both had a direct effect on the period of time required for glass eel sorting during which by-catch fish were exposed to air and suffered from very aggressive sorting procedures that caused severe external and internal injuries. By-catch fish measuring less than 40 mm L T were more susceptible to glass eel fishery procedures than those larger (>60 mm L T), independent of the species considered or their stage of development. This fishery, similar to other ones, should strive to minimization the amount of discards and the mortality of discarded fish, by improving the selectivity of the fish trap and developing new sorting and selection procedures. [ABSTRACT FROM AUTHOR]

Coastal wetland stability and structure can be significantly affected by littoral processes when they are close to the shoreline. Thus, under certain conditions, the combination of shoreline dynamics and direct wave action during storms can influence the stability of marshes and vegetation community composition. This interaction between littoral dynamics and coastal wetlands is illustrated by analysing processes taking place in the Buda Island (Ebro delta, NW Spain), where a coastal lagoon very close to a retreating shoreline exists. Two main time scales have been found to be relevant for interaction of coastal processes with ecosystem dynamics, the decadal and episodic scales. The decadal scale determines the average trend in beach width and directly controls the potential loss of wetland surface. The episodic scale is linked to the occurrence of wave and storm surge events and it determines a pulsing stress in the ecosystem through flooding, being key parameters to determine their direct influence the intensity and repetition of these events. [ABSTRACT FROM AUTHOR]

The lacustrine facies from two sections (Candasnos and Fraga) ofthe Oligocene-Miocene Torrente de Cinca lithostratigraphic Unit in thecentral part of the Ebro Basin (Spain) have been analysed to determine theinfluence of orbital parameters in lacustrine sedimentation. The unit ispredominantly composed of limestones and marls, and represents a shallowlacustrine freshwater system. The sedimentological features of the faciesstudied demonstrate that the lower part of the Candasnos section representsoffshore lacustrine subenvironments whereas the upper part, and the whole ofthe Fraga section, characterise marginal lacustrine areas. Series of stratalthickness variations of limestone, marl, and limestone/marl couplets fromboth sections have been analysed using spectral analysis. This shows thatinformation corresponding to periodic cycles only appears in the offshorefacies, that is to say, in the lower part of Candasnos section, and disappearsin the marginal facies where non-periodic cycles exist. Furthermore, thespectral analysis of the offshore facies highlights the existence of a peak inthe power spectrum with a period of around 7 (6.8 to 7.8) that can berecognised in the field as shallowing-upward lacustrine sequences.Magnetostratigraphic data from the Candasnos section allow us to establish atime span of 2,808 years for the limestone/marl couplet from the lower partof this section, and between 19,000 and 22,000 years for the periodic cycleidentified, thus representing the climatic precession cycle. Shallowingsequences from marginal areas do not correspond with any periodiccycle. [ABSTRACT FROM AUTHOR]

The article presents a study that determined the levels of mercury, lead (Ld), cadmium (Cd), copper, and zinc (Zn) in water, sediments and earthworms along Ebro River in Spain. Samples were collected from 17 stations with suspected sources of agricultural, urban or industrial pollution. To ensure the representativity of samples, bulk sediments were obtained by mixture of various cores collected at every station. Results of the study showed that the levels in earthworms do not consistently reflect the levels of metal contamination present in the surrounding sediments. Also, the sediment samples showed relatively high pH values and greater accumulations of Cd, Zn, and Pb by earthworms in soil with a low pH value.

The article focuses on sequential extraction of copper, lead, cadmium, and zinc metal pollution in sediments sampled along the Ebro river, Spain which is affected by inputs of agriculture, urban and industrial pollutants. Several sequential extraction protocols based in a sequence of reagents of increasing reactivity have been proposed to determine the chemical form of metals in the sediments. They have also investigated the relationships between the trace metal partitioning in sediments and their accumulation in earthworms living in these sediments.