Ebro River Research Articles

The effect of wildfires on flood risk: a multi-hazard flood risk approach for the Ebro River basin, Spain

Abstract. Climate change increases the risk of wildfires and floods in the Mediterranean region. Yet, wildfire hazards are often overlooked in flood risk assessments and treated in isolation, despite their potential to amplify floods. Indeed, by altering the hydrological response of burnt areas, wildfires can lead to increased runoff and amplifying effects. This study aims to comprehensively assess flood risk using a multi-hazard approach, considering the effect of wildfires on flood risk, and integrating diverse socio-economic indicators with hydrological properties. More specifically, this study investigates current and future flood risks in the Ebro River basin in Spain for the year 2100 under the Shared Socioeconomic Pathway 1-2.6 (SSP1-2.6) and SSP5-8.5 scenarios, taking into account projected socio-economic conditions and the effect of wildfires. An analytical hierarchy process (AHP) approach is employed to assign weights to various indicators and components of flood risk based on insights gathered from interviews with seven experts specializing in natural hazards. Results show that the influence of wildfires on the baseline flood risk is not apparent. Under the SSP1-2.6 scenario, regions with high flood risk are expected to experience a slight risk reduction, regardless of the presence of wildfires, due to expected substantial development in adaptive capacity. The highest flood risk, almost double compared to the baseline, is projected to occur in the SSP5-8.5 scenario, especially when considering the effect of wildfires. Therefore, this study highlights the importance of adopting a multi-hazard risk management approach, as reliance solely on single-risk analyses may lead to underestimating the compound and cascading effects of multi-hazards.

Urban Planning and Landscape Projects on Urban Riverbanks in Europe: Comparative Study of the Ebro River, Zaragoza, and the Isar River, Munich

The tension between rivers and cities reaches its highest expression in urban river basins. Given the high level of interaction between natural and cultural factors in many riverfronts, an integral project design is essential. The large number of urban river basin enhancement cases that have been conducted has resulted in a large amount of urban scientific literature. The multifaceted nature of these systems renders their analysis and contextualization a challenging endeavor. The objective of this research is to propose a novel evaluation tool based on a reformulation of Lynch’s theory of urban form performance, which has been updated from a landscape urbanism perspective. The conceptual framework provides a comprehensive method for translating diverse design strategies into comparable and meaningful categories. The results illustrate the impact of urban riverbank requalification initiatives on the formal quality dimensions of the city–river socio-ecological system. The assessment tool was applied to two cases: the Ebro River in Zaragoza (Spain) and the Isar River in Munich (Germany). Despite differences between the cases, comparative analysis revealed similar levels of urban landscape quality parameters and common elements that can provide new insights when considering the solutions applied and the degree of improvement in quality and river–city cohesion achieved with these projects.

“Liquid assets”: Coastal wetlands, regional parks, and the protection of Mediterranean deltas

After a century of accelerating drainage, in the 1960s coastal wetlands became the object of unprecedented protection campaigns around the world. This paper compares the history of three successful cases of coastal wetland protection in the Mediterranean between the 1960s and 1980s: the Rhône (France), Po (Italy), and Ebro (Spain) River deltas. As most of the coast of Mediterranean Europe, these three cases were at the center of renewed redevelopment attempts, to further expand intensive agriculture, industry, and seaside tourism, which invariably involved wetlands drainage. In these three cases, protection was achieved by establishing “regional parks” in the deltas. We argue that it was not by chance. Wetland advocates at the international, national, and local scales coated their plea for protection in the language of economics, making the case for wetlands’ value as “liquid assets.” They argued that wetland protection could rhyme with development and, abandoning initial projects to protect deltas as national parks, focused their efforts on creating regional parks instead. Stemming from the European regional planning movement, the regional park framework proved expedient to combine development expectations and wetland protection. Thanks to modular land use zoning, it promised to combine productive activities with protected areas, without imposing uniform restrictions on the entire deltas such as those often associated with national parks. The history of these three coastal parks, therefore, sheds light on the counterintuitive but strong relationship existing between coastal development and protection by uncovering the discursive strategies and unlikely coalitions that made conservation possible.

THE VERTEBRATE FAUNA OF THE LOWER PLIOCENE CONTINENTAL DEPOSITS IN THE EBRO DELTA (BAIX EBRE BASIN, NE SPAIN)

The Pliocene faunas of the northeastern Iberian Peninsula are poorly known due to the scarcity of deposits from this interval. In this context, the site of Sant Nofre-Campredó (Baix Ebre, Catalonia, Spain), comprising two contemporaneous outcrops belonging to geologically correlated sections (Sant Nofre and Campredó-Via Fèrria), makes a significant contribution to the study of Pliocene faunas in this region. The first vertebrate remains were recovered in the late 1970s in clay deposits close to the Sant Nofre Hill. Later, intensive sampling in the 1980s at the Campredó-Via Fèrria outcrop led to the recovery of more than a hundred fossil specimens, including small vertebrates and large mammals. Here, we revise these collections to expand and update the vertebrate list, better constrain the age of the continental deposits, and characterize the environment and climate around the mouth of the Ebro River during the formation of the site. Up to 24 vertebrate species have been identified at Sant Nofre-Campredó, including amphibians, reptiles, and mammals. The presence of the rodents Paraethomys baeticus Piñero & Verzi, 2020, Apocricetus barrierei (Mein & Michaux 1970), and Occitanomys brailloni Michaux, 1969 implies an early Ruscinian age (MN14 unit) for the two outcrops. Biostratigraphic correlations with other well-dated sites in the Iberian Peninsula refine the estimated age of Sant Nofre-Campredó to approximately 4.6 Ma. The ecological affinities of the identified fauna reveal a landscape dominated by woodland habitats in the surroundings of the site during the Early Pliocene, with presence of open humid meadows and water bodies under warm and moist climatic conditions.

Analysis and forecast of crop water demand in irrigation districts across the eastern part of the Ebro river basin (Catalonia, Spain): estimation of evapotranspiration through copernicus-based inputs

AbstractThe agricultural sector is currently facing the uncertainty that accompanies climate change in terms of the availability of water resources, as well as the need to balance the water demand for agricultural irrigation with other uses in river basins. In Spain, irrigation districts (IDs) play a very important role in the management of water resources. The efficiency of ID water management involves finding an equilibrium between supply and demand. It is in relation to the latter where the uncertainty is greatest, because until now no tools have been available to characterize water demands with sufficient precision throughout irrigation campaigns. ID managers need precise information and the development of tools to support decision making in planning and water management. Therefore, this study aims to identify, compare and analyse the differences between the demands, allocations and consumptions of water for irrigation in different IDs of the eastern part of the Ebro basin during six consecutive growing seasons. In addition, projections of water demands up to 2100 are conducted using a dataset of six global climate models under different climate scenarios. Novel advances in remote sensing for evapotranspiration approaches using Copernicus-based inputs were used in this study. Large variabilities in water demands among IDs and in the adjustments between demands and allocations were observed, suggesting there is still much room for the improvement of water management. All climate projections have a very clear pattern indicating an upward trend in water demands until the end of the century.

Agricultural Runoff Effects on Leaf Litter Decomposition: A Comparative Study in Natural and Constructed Deltaic Mediterranean Wetlands

Wetlands, widely distributed and hotspots of biodiversity, play a crucial role in global biogeochemical cycles and human well-being. However, despite their ecological importance, wetlands worldwide are under threat due to widespread conversion into agricultural fields, leading to changes in hydrology, increased salinity, and more frequent eutrophication. In response to these challenges, constructed wetlands are created to treat agricultural wastewater and mitigate eutrophication. This study aims to assess the effect of natural vs. constructed wetlands on ecosystem functioning (organic matter decomposition of the dominant vegetation: Phragmites australis and Typha angustifolia). We conducted this study in the Ebro River Delta (NE Spain), which represents a deltaic wetland affected by agricultural land-use changes, examining two constructed and two natural wetlands. Our findings indicate that the influence of agricultural runoff on the decomposition process was similar in both types of wetlands, suggesting that freshwater agricultural runoff has a consistent effect on ecosystem functioning, regardless of its origin, natural vs. constructed. Differences in macroinvertebrate communities associated with leaf litter were likely due to specific conductivity but did not impact decomposition rates. The estimated time required to decompose 95% of the T. angustifolia litter produced annually in the studied wetlands ranged from 288 to 856 days. In constructed wetland, this decomposition time exceeded one year, contributing to soil formation and carbon sequestration in wetland ecosystems. Our study suggests that the utilization of constructed wetlands for treating agricultural runoff can aid in mitigating the impacts of agricultural land use in these areas.

Irrigation modernization in the Ebro – Aragón region of Spain: Past and future trends

Irrigation modernization has been analyzed in the part of the Aragón region within the Ebro River Basin, in northeastern Spain. A geodatabase was built with 1144 irrigation cartographical units (ICUs) adding up to 476 k ha with access to water and equipped with on-farm irrigation hardware. ICUs were classified in eight categories related to irrigation modernization. The classification revealed that in the past two decades an integral irrigation modernization was achieved in 103 k ha. In a second modernization, 13 k ha were transformed to reduce their dependence on grid energy. A third type of modernization, oriented to the digitalization of irrigation management processes, is only incipient at this time. Public investments in modernization during this period were estimated at 36.8 M€/year. This intense, publicly co-funded, policy-driven process will be far from sufficient to complete the modernization of all irrigated land in the study area in another twenty-year period. In a concurrent process, obsolete, socially unfavored and structurally deficient irrigated areas are being abandoned for irrigation and even for farming. Specific indicators were proposed to approach the abandonment process, revealing that irrigation intensity in temperate climate, riparian ICUs was only 20 %. Irrigation in the study area needs to progress towards sustainable intensification, concentrating agricultural production in areas equipped with the technology and the water management capacities required to face the current agronomical and environmental challenges. The on-going processes of irrigation modernization, new irrigation developments and irrigation abandonment should be coordinated to serve this purpose.

Forecast of chlorophyll-a concentration as an indicator of phytoplankton biomass in El Val reservoir by utilizing various machine learning techniques: A case study in Ebro river basin, Spain

The trophic condition of bodies of water, such as oceans, lakes, and reservoirs, can be accurately assessed thanks to the use of chlorophyll-a, or Chl-a, as an indicator of phytoplankton biomass and abundance. In fact, the main molecule in charge of photosynthesis is Chl-a. This work presents a powerful and reliable nonparametric method for predicting the concentration of Chl-a in El Val reservoir using a dataset containing 240,765 samples: the Support Vector Regression (SVR) with different kinds of kernels. This mathematical SVR-relied model was constructed using five years (2018–2022) of water quality variable monitoring (physico-chemical independent variables) in the El Val reservoir (located in the northeast of Spain). For comparison, M5 model trees, a the Multilayer Perceptron (MLP), that is a particular type of artificial neural network (ANN), and multivariate linear regression (MLR) were also used for the same observed data. The Grid Search (GS) algorithm was employed as an optimizer; this approach greatly improves the regression precision by allowing the optimal kernel parameters to be chosen during the SVR training phase. There are two ways to sum up the findings of this investigation. First, it is determined how relevant each input variable is to the Chl-a concentration in the El Val reservoir. Second, this hybrid GS/SVR-relied model with PUK kernel can accurately predict the Chl-a (R2 and r values were 0.8989 and 0.9499, respectively). The model’s agreement with the observed data amply proves the remarkable efficacy of this creative strategy.

Massive decline of invasive apple snail populations after blue crab invasion in the Ebro River, Spain

The negative interaction between multiple invasive species, when an invasive predator benefits from a previously introduced and abundant prey, poses unanticipated challenges for the joint management of invaders. To illustrate this question, we describe the surge and collapse of the invasive apple snail Pomacea maculata population before and after the arrival of the invasive blue crab, Callinectes sapidus, in the Ebro River (NE Spain). These two invaders have coincided for the first time beyond their respective native and prior invasive ranges, and thus lack any previous shared eco-evolutionary history facilitating coexistence. We leverage data from a 9-year apple snail removal programme (2014–2022) conducted by authorities to evaluate the effectiveness of the management programme and describe the apple snail temporal dynamics in the Ebro River. Since its arrival in 2013, the apple snail population increased exponentially along the river and adjacent rice-fields despite labour-intensive eradication efforts. Unexpectedly, riverine populations of the apple snail declined by 90% in 2018 relative to the prior year without apparent association with previous management efforts. Simultaneously, the blue crab was first recorded in the Ebro River in 2018, and its distribution rapidly overlapped the whole area invaded by apple snails. We suggest that over-predation by the blue crab is the main cause of the decline observed in the apple snail, and discuss the implications of this new invader-invader interaction for management. This study underscores the unforeseen consequences of subsequent waves of invasion, and the importance of supporting management with a deeper understanding of ecological interactions among invasive predator and prey species.

Far‐reaching blues: Long‐distance migration of the invasive Atlantic blue crab

Abstract Upstream migration of the Atlantic blue crab Callinectes sapidus is well described in its native range, but it is little known in invaded areas. Here, we report several long‐distance migration events of the blue crab in the Iberian Peninsula and use a global database to calculate the probability of occurrence of the species in relation to distance to sea. We then exemplify the potential of blue crab impacts on freshwaters by overlapping its probability of occurrence with that of the critically endangered European eel Anguilla anguilla. Finally, we evaluate the extent to which dam barriers can halt the upstream migration of the blue crab. Invasive blue crab has been detected at 108 km from the sea in the Guadalquivir River (the farthest distance reported in the non‐native range), at 71 km in the Guadiana River and at 53 km in the Ebro River. The probability of occurrence decreased steeply in the first upstream kilometres, but it is still concerning at a dozen kilometres from the river mouth (50% at 19 km, 25% at 38 km, and 3% at 100 km). The blue crab invasive potential widely overlaps (63%) with the Iberian range of the European eel. The blocking effect of dams on the potential invasion of freshwater systems by the blue crab was limited (13%). Our study highlights the need to study the upstream migration of the blue crab within its non‐native range, since it could involve serious impacts in reachable river and stream habitats.

Mercury stable isotopes in seabirds in the Ebro Delta (NE Iberian Peninsula): Inter-specific and temporal differences

Mercury (Hg) is a global pollutant, which particularly affects aquatic ecosystems, both marine and freshwater. Top-predators depending on these environments, such as seabirds, are regarded as suitable bioindicators of Hg pollution. In the Ebro Delta (NE Iberian Peninsula), legacy Hg pollution from a chlor-alkali industry operating in Flix and located ca. 100 km upstream of the Ebro River mouth has been impacting the delta environment and the neighboring coastal area. Furthermore, levels of Hg in the biota of the Mediterranean Sea are known to be high compared to other marine areas. In this work we used a Hg stable isotopes approach in feathers to understand the processes leading to different Hg concentrations in three Laridae species breeding in sympatry in the area (Audouin's gull Ichthyaetus audouinii, black-headed gull Chroicocephalus ridibundus, common tern Sterna hirundo). These species have distinct trophic ecologies, exhibiting a differential use of marine resources and freshwater resources (i.e., rice paddies prey). Moreover, for Audouin's gull, in which in the Ebro Delta colony temporal differences in Hg levels were documented previously, we used Hg stable isotopes to understand the impact of anthropogenic activities on Hg levels in the colony over time. Hg stable isotopes differentiated the three Laridae species according to their trophic ecologies. Furthermore, for Audouin's gull we observed temporal variations in Hg isotopic signatures possibly owing to anthropogenic-derived pollution in the Ebro Delta. To the best of our knowledge this is the first time Hg stable isotopes have been reported in seabirds from the NW Mediterranean.

Temporal mercury dynamics throughout the rice cultivation season in the Ebro Delta (NE Spain): An integrative approach

During the last few decades, inputs of mercury (Hg) to the environment from anthropogenic sources have increased. The Ebro Delta is an important area of rice production in the Iberian Peninsula. Given the industrial activity and its legacy pollution along the Ebro river, residues containing Hg have been transported throughout the Ebro Delta ecosystems. Rice paddies are regarded as propitious environments for Hg methylation and its subsequent incorporation to plants and rice paddies' food webs. We have analyzed how Hg dynamics change throughout the rice cultivation season in different compartments from the paddies' ecosystems: soil, water, rice plants and fauna. Furthermore, we assessed the effect of different agricultural practices (ecological vs. conventional) associated to various flooding patterns (wet vs. mild alternating wet and dry) to the Hg levels in rice fields. Finally, we have estimated the proportion of methylmercury (MeHg) to total mercury in a subset of samples, as MeHg is the most bioaccumulable toxic form for humans and wildlife. Overall, we observed varying degrees of mercury concentration over the rice cultivation season in the different compartments. We found that different agricultural practices and flooding patterns did not influence the THg levels observed in water, soil or plants. However, Hg concentrations in fauna samples seemed to be affected by hydroperiod and we also observed evidence of Hg biomagnification along the rice fields’ aquatic food webs.

Satellite Radar Altimetry Supporting Coastal Hydrology: Case Studies of Guadalquivir River Estuary and Ebro River Delta (Spain)

Satellite Radar Altimetry Supporting Coastal Hydrology: Case Studies of Guadalquivir River Estuary and Ebro River Delta (Spain)

Angler’s preferences, perceptions and practices regarding non-native freshwater fish

It is globally recognized that freshwater anglers can have a decisive role in promoting fish introductions. The aim of this study was to analyze freshwater anglers’ actions and perceptions regarding fish introductions, comparing two distinct situations, one with recently arrived non-natives fishes and another with older fish introductions, using the Iberian Peninsula as a case study. To achieve this goal, a bilingual survey was implemented on-line in Portugal and Spain and in person (direct inquiries) in two Iberian regions: Lower Ebro (older fish introductions) in Spain; and Lower Tagus (recent fish introductions) in Portugal. Results showed spatial differences in perceptions and actions, namely about the target species, awareness of the impact of non-native fishes, fish introductions reported and proportion of anglers that wanted new fish species. In the Ebro river there is a high percentage of foreign anglers, higher awareness of fish introduction impact and lower introduction rates reported than in the Tagus river. However, popularity of non-native species like European catfish, was higher in the Ebro. In general, although risk behaviors such as use of fish as life bait was of low prevalence for both countries (approx. 5%), it corresponds to large numbers of fish being introduced. Our conservative estimates revealed 273,600 events of bait discharge per year. Regarding the intentional introductions, we estimated a total of 140,000 intentional introduction (illegal) events per year. These findings may help to improve monitoring, awareness and fisheries management programs led by governmental agencies.Graphical abstract

Data treatment and corrections for estimating H2O and CO2 isotope fluxes from high-frequency observations

Abstract. Current understanding of land–atmosphere exchange fluxes is limited by the fact that available observational techniques mainly quantify net fluxes, which are the sum of generally larger, bidirectional fluxes that partially cancel out. As a consequence, validation of gas exchange fluxes applied in models is challenging due to the lack of ecosystem-scale exchange flux measurements partitioned into soil, plant, and atmospheric components. One promising experimental method to partition measured turbulent fluxes uses the exchange-process-dependent isotopic fractionation of molecules like CO2 and H2O. When applying this method at a field scale, an isotope flux (δ flux) needs to be measured. Here, we present and discuss observations made during the LIAISE (Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment) 2021 field campaign using an eddy covariance (EC) system coupled to two laser spectrometers for high-frequency measurement of the isotopic composition of H2O and CO2. This campaign took place in the summer of 2021 in the irrigated Ebro River basin near Mollerussa, Spain, embedded in a semi-arid region. We present a systematic procedure to scrutinise and analyse measurements of the δ-flux variable, which plays a central role in flux partitioning. Our experimental data indicated a larger relative signal loss in the δ fluxes of H2O compared to the net ecosystem flux of H2O, while this was not true for CO2. Furthermore, we find that mole fractions and isotope ratios measured with the same instrument can be offset in time by more than a minute for the H2O isotopologues due to the isotopic memory effect. We discuss how such artefacts can be detected and how they impact flux partitioning. We argue that these effects are likely due to condensation of water on a cellulose filter in our inlet system. Furthermore, we show that these artefacts can be resolved using physically sound corrections for inlet delays and high-frequency loss. Only after such corrections and verifications are made can ecosystem-scale fluxes be partitioned using isotopic fluxes as constraints, which in turn allows for conceptual land–atmosphere exchange models to be validated.

Local hydrodynamic in coastal system affects the coccolithophore community at a short spatial scale

Coccolithophores are an ecologically and biogeochemically important group of calcifying marine plankton, contributing globally to both the organic carbon pump and the carbonate counter pump. Understanding their distribution in today's ecosystems is crucial for both paleoenvironmental reconstruction and for predicting their fate under climate change and environmental pollution. Traditionally regarded as open ocean dwellers, more recent studies have highlighted their importance in coastal systems.Here we describe the coccolithophore community in the Catalan Sea (Northwestern Mediterranean), off the Ebro River Delta, based on an oceanographic survey conducted in autumn 2019. We identify three environmentally distinct regimes: mixed (mostly shallow), transition (upper photic layers offshore), and stratified deep waters (below 75 m). Total coccolithophore density is driven by E. huxleyi and peaks in the mixed zone where nutrient concentrations are low, but nitrite concentrations are high. We propose that peak cell densities are partly explained by a switch from nitrate to nitrite usage similarly to diatoms behavior. Species diversity peaks in deeper offshore waters due to vertical stratification. Helicosphaera carteri and Algirosphaera robusta benefit from Emiliania huxleyi decrease both in coastal and offshore environment.

How does the type of MCDM method affect the results of the prioritization and assessment of ecosystem services? A case study in the Ebro River Delta (Spain)

The prioritization and assessment of ecosystem services allow governments to apply public policies on target to improve these natural areas' sustainable development and human well-being. It also enhances the environmental, socio-cultural and agricultural management of ecosystems. Previous research has proved that geographical and socio-cultural factors could influence the results obtained in real study cases. However, other factors should be studied since stakeholders have differing views on the most suitable method to prioritize ecosystem services. Regarding how stakeholders structure criteria, networked processes are, theoretically, more appropriate than the hierarchical techniques such as AHP, since they capture all the relationships among criteria. Consequently, nowadays ANP has become one of the most common MCDM methods in this field. Moreover, this technique also analyzes the consistency of the decision-makers' judgements. Nonetheless, the use of this method also encompasses some weak points: it is too laborious and time-consuming. Additionally, it is not easy to manage when the number of criteria per cluster is too large. It is why some researchers prefer using other techniques such as AHP in spite of the fact that it does not capture the relationships among criteria, or a hybrid DEMATEL-Based ANP technique, better-known as DANP, which does not utilize pairwise comparisons and hence is not able to study judgments’ inconsistencies. Therefore, this study aims to analyze how each method (AHP, ANP and DANP) influences the prioritization of ecosystem services in a real case conducted in the Ebro River Delta (Spain). Once all priorities are obtained, the results are compared through a statistical analysis of compatibility and correlation. Regarding the results of the three techniques, they show no compatibility among them. However, the correlation between the rankings obtained with ANP and DANP is reasonably correlated for seven of the eleven experts participating in the study. Besides, when the results are aggregated, their compatibility and correlation increase. On the contrary, the results obtained in AHP differ from the other two methods. Finally, and contrary to the initial hypothesis, most experts agreed more with the results obtained with DANP and AHP than with ANP.

Comparative analysis of historical human and biogeomorphic interactions in large river-floodplain systems under different climate contexts

Worldwide, trajectories of deterioration of large rivers’ natural structure and functioning have been described and related to anthropogenic pressures acting at different spatio-temporal scales. However, the variety of methodologies, time-scale resolutions and the lack of standard indicators frequently hinder the comparison of outcomes among rivers in different geographic and climatic regions. Covering between 204 and 36 years, this study applied the same multi-temporal analysis of riverine trajectories (i.e., anthropization, changeless, progression, and regression) in five large river segments within temperate (Rhine River, France and Germany), Mediterranean (Ebro and Tagus Rivers, Spain), and semi-arid climates (Aras and the Zayandeh-rud Rivers, Iran). This transferable GIS-based method includes the assessment of historical balances within natural dynamics (Natural Trajectory Index, NTI), the degree of anthropization (Anthropization Ratio, AR), and the degree of stability (Stability Ratio, SR) in the studied river-floodplain systems.Results show similarities among the European case studies (i.e., Rhine, Ebro and Tagus rivers) in response to hydromorphological impacts, with percentage increases in human-induced changes (i.e., anthropization), and habitat development (i.e., progression). Apart from the Zayandeh-rud River, that presents a marked tendency toward progression, processes of habitat rejuvenation (i.e., regression) have almost disappeared in all case studies, and riverine forms remain unchanged. The differences found between the European and the Asian case studies are considered related to the aims and methods of engineering choices for historical river management, with a long history of river reprofiling and impounding in European rivers, while Iranian regulation is relatively recent, and involves extensive inter-basin water transfers.

Where have all the sediments gone? Reservoir silting and sedimentary justice in the lower Ebro River

At the intersection of natural and social sciences, interest in river sedimentary fluxes and their alteration by human activities is increasing in the context of general retreat of delta formations. Since the 1950s, the construction of large dams in the main course of rivers has produced, among other impacts, a radical decrease in sedimentary fluxes — a key factor in the worldwide sedimentary crisis. While sediment accumulates in reservoirs, the resulting sediment scarcity downstream contributes to land subsidence and coastal erosion, endangering livelihoods in low lying areas such as river deltas. Focusing on the case of the Ebro River and delta (Spain), this article builds on Katherine Dawson's notion of sedimentary justice to examine the articulation of a social demand to mobilise the sediments trapped in reservoirs to counter delta subsidence and coastal erosion. Using a historical perspective and paying attention to matters of both sediment quantity and quality, we show how this demand has developed hand in hand with the emergence of a scientific interpretation of the Ebro delta's origins that emphasises non-human forces and the importance of sedimentary fluxes before human interferences. Activists have taken up this argument to demand the restoration of sedimentary fluxes, exposing corporate hydropower interests and insisting on the mobilisation of sediment trapped in reservoirs. Overall, by scrutinizing the power relations embedded in the immobilization of river sediments, this article contributes to recent work that integrates the materiality of sediment to the hydrosocial framework of analysis and argues that sedimentary justice provides new avenues to incorporate the non-human world to the literature on environmental and water justice.

Fate of pharmaceuticals in the Ebro River Delta region: The combined evaluation of water, sediment, plastic litter, and biomonitoring

The increasing consumption of pharmaceuticals, alongside their limited removal in wastewater treatment plants (WWTPs), have led to their ubiquitous occurrence in receiving aquatic environments. This study addresses the occurrence of 68 pharmaceuticals (PhACs) in the Ebro River Delta region (NE Spain), as well as their distribution in different environmental compartments, including surface water, sediments, biota (river biofilm and fish tissues), and field-collected plastic litter. In addition, their concentrations in serving WWTPs, as possible sources of environmental contamination, were also determined.Our study confirmed the widespread occurrence of PhACs in riverine and, to a more limited extent, coastal environments. Most frequently detected PhACs belonged to analgesics/anti-inflammatories (e.g., ibuprofen) and psychiatric drugs (e.g., venlafaxine) therapeutic groups, followed by antihypertensives (e.g., valsartan) and antibiotics (e.g., azithromycin). Seasonal differences in cumulative levels of PhACs were reported for water and sediments (winter>summer). Despite spatial gradients were not clear along the river, a non-negligible contribution of upstream Ebro sites (reference area) was highlighted, which was unexpected based on the low anthropogenic pressure. Sediments represented a minor attenuation pathway for the selected PhACs, whereas they were more heavily accumulated in biota: fish liver (up to 166 ng/g dw), river biofilms (up to 108 ng/g dw), fish plasma (up to 63 ng/mL), and fish muscle (up to 31 ng/g dw).These findings highlight the importance of biomonitoring in the characterization of polluted areas and prioritization of hazardous substances (e.g., psychiatric drugs) in aquatic systems, and a particular interest of fish plasma as non-destructive biomonitoring matrix. PhACs were also detected on plastic litter, demonstrating their role as environmental sinks for certain PhACs (e.g., analgesics/anti-inflammatories, psychiatric drugs). Overall, the widespread detection of PhACs in a variety of biotic and abiotic matrices from the lower Ebro River and Delta warns about their possible environmental implications.