Rivers In Spain Research Articles

Estimation of high return period flood quantiles using additional non-systematic information with upper bounded statistical models

Abstract. This paper proposes the estimation of high return period quantiles using upper bounded distribution functions with Systematic and additional Non-Systematic information. The aim of the developed methodology is to reduce the estimation uncertainty of these quantiles, assuming the upper bound parameter of these distribution functions as a statistical estimator of the Probable Maximum Flood (PMF). Three upper bounded distribution functions, firstly used in Hydrology in the 90's (referred to in this work as TDF, LN4 and EV4), were applied at the Jucar River in Spain. Different methods to estimate the upper limit of these distribution functions have been merged with the Maximum Likelihood (ML) method. Results show that it is possible to obtain a statistical estimate of the PMF value and to establish its associated uncertainty. The behaviour for high return period quantiles is different for the three evaluated distributions and, for the case study, the EV4 gave better descriptive results. With enough information, the associated estimation uncertainty for very high return period quantiles is considered acceptable, even for the PMF estimate. From the robustness analysis, the EV4 distribution function appears to be more robust than the GEV and TCEV unbounded distribution functions in a typical Mediterranean river and Non-Systematic information availability scenario. In this scenario and if there is an upper limit, the GEV quantile estimates are clearly unacceptable.

Temporal variability in the thermal regime of the lower Ebro River (Spain) and alteration due to anthropogenic factors

Summary The Ebro River is one of the longest rivers in Spain and it also has the greatest discharge. Its lower part is highly regulated and includes a system of three reservoirs (Mequinensa, Riba-roja and Flix). The water temperature is altered because of the release of hypolimnetic water and the use of water for cooling at the Asco nuclear power plant. The thermal regime of the lower Ebro River on different time scales and the changes caused by anthropogenic factors, especially the system of reservoirs and the thermal effluent of the nuclear power plant, have been studied by installing a net of water temperature measuring stations and by using historical water temperature data provided by the thermal power plant at Escatron. An increase of 2.3 °C in the mean annual water temperature could be demonstrated in the period 1955–2000 at this site. The effects of the system of reservoirs and of the nuclear power plant were the usual for this kind of structures and could be detected many kilometres downstream. In the summer, the cooling effect of the reservoirs and the warming effect of the nuclear power plant compensated each other. In winter, the warming effect of both summed up.

The impact of late Holocene climatic variability and land use change on the flood hydrology of the Guadalentín River, southeast Spain

The Guadalentín River, located in southeast Spain, is considered one of the most torrential rivers in Spain, as indicated by catastrophic events such as the 1879 flood that caused 777 fatalities in the Murcia region. In this paper, flood frequency and magnitude of the upper Guadalentín River were reconstructed using geomorphological evidence, combined with one-dimensional hydraulic modelling and supported by records from documentary sources at Lorca in the lower Guadalentín catchment. Palaeoflood studies were conducted along a 2.5-km reach located at the confluence of the Rambla Mayor (162 km 2) and Caramel River (210 km 2). These tributaries join at the entrance of a narrow bedrock canyon, carved in Cretaceous limestone, which is 15–30 m wide and 40 m deep. Six stratigraphic profiles were described, the thickest and most complete corresponding to flood benches deposited upstream of the canyon constriction. The stratigraphic and documentary records identify five main phases of increased flood frequency. Phase 1, based on sedimentary palaeoflood evidence alone, occurred at c. AD 950–1200 with at least ten floods with minimum discharge estimates of 15–580 m 3 s − 1 . Phases 2–5, identified through combined sedimentary and documentary evidence occurred at: (a) AD 1648–1672, with eight documentary floods and two palaeofloods exceeding 580–680 m 3 s − 1 (most probably the AD 1651 and 1653 events); (b) AD 1769–1802, comprising seven documentary floods, of which at least two events (> 250 m 3 s − 1 ) are preserved in the sedimentary record; (c) AD 1830–1840, with four documentary floods, and at least two events recorded in the stratigraphy (760–1035 m 3 s − 1 ); and finally (d) the AD 1877–1900 period that witnessed seven documentary floods, with three palaeofloods exceeding 880 m 3 s − 1 . The palaeoflood and historical flood information indicate an anomalous increase in the frequency of large magnitude floods between AD 1830 and 1900, which can be attributed to climatic variability accentuated by intensive deforestation and land use practices during the first decades of the nineteenth century.

Use of macroinvertebrate-based multimetric indices for water quality evaluation in Spanish Mediterranean rivers: an intercalibration approach with the IBMWP index

For the European Parliament and Commission to implement the Water Framework Directive (WFD), the water-quality indices that are currently used in Europe need to be compared and calibrated. This will facilitate the comparative assessment of ecological status throughout the European Union. According to the WFD, biologic indices should respond consistently to human impacts, using multimetric approaches and water-quality classification boundaries adjusted to a common set of normative definitions. The European Commission has started an intercalibration exercise to review biologic indices and harmonize class boundaries. We used data from rivers in Spain to compare the IBMWP (Iberian Biological Monitoring Working Party) index, which is commonly used by water authorities in Spain and by several research centers, with the Intercalibration Common Multimetric Index (ICM-Star), which was used as a standard in the intercalibration exercise. We also used data from Spanish rivers to compare the multimetric indices ICM-7 (based on quantitative data) and ICM-9 (based on qualitative data) with the IBMWP. ICM-7 and ICM-9 were proposed by the Mediterranean Geographical Intercalibration Group (Med-GIG). Additionally, we evaluated two new multimetric indices, developed specifically for macroinvertebrate communities inhabiting Mediterranean river systems. One of these is based on quantitative data (ICM-10), while the other is based on qualitative data (ICM-11a). The results show that the IBMWP index responds well to the stressor gradient present in our data, and correlates well with ICM-Star. Moreover, the IBMWP quality class boundaries were consistent with the intercalibration requirements of the WFD. However, multimetric indices showed a more linear relation with the stressor gradient in our data, and less variation in reference values. In addition, they may provide more statistical power for detecting potential environmental impacts. Multimetric indices produced similar results for quantitative and qualitative data. Thus, ICM-10 (also named IMMi-T) and ICM-11a (also named IMMi-L) indices could be used to meet European Commission requirements for assessing the water quality in Spanish Mediterranean rivers.

Viaduct over the Nalón River in Spain – A new experience with ‘strict box’ composite bridges

AbstractThe motorway viaduct over the Nalón River is 1100 m long and 27 m wide. The longitudinal structural system consists of a single strict composite box that takes advantage of the different properties of structural steel and concrete, going beyond the double composite action systems already in use for a long time. The box girder is enlarged by means of composite trusses connected to the upper slab at both sides of the deck. Longitudinally, the structure can be divided into two sections:– a 660 m long curving approach section over the river plain– a 440 m long straight section crossing the riverbed. The central part of this section is a 124 m span rigid frame composed of a box girder with varying depth and two elegant piers, one on each side of the river.The bridge was constructed by launching from both abutments. The launching of the main section, due to the varying depth of the box girder in the main span, required longitudinal auxiliary elements in order to launch it in the same way as the spans of constant depth. A temporary pier was built in the middle of the river in order to reduce the cantilever in the main span to a moderate length. The viaduct construction was completed in May 2007.

Automatic Control of Flows and Levels in an Irrigation Canal

Modernization of irrigation canals is becoming a strategic issue in many areas of the world with the purpose of improving the efficiency and the operational flexibility in water delivery. Apparently, small deviations in keeping flows at the desired scheduled values can lead to significant waste of water, which is particularly important in arid countries and dry periods. Automatic control systems are being considered as the alternative to increase the low performance of traditional manual operations. This paper describes the implementation of two control systems in the so-called Canal de Lodosa, one of the canals that convey irrigation water from the Ebro River in Spain. The systems are designed using classical proportional-integral and adaptive predictive control, respectively, which are two of the methodologies mostly used in process control in different industrial areas nowadays. This paper introduces the canal-control problem and the models to describe the dynamic behavior, including experimental identification. The designs of both control schemes are described, and field implementation results are presented and comparatively discussed in terms of performance, control efforts, and working load.

Trophic Behavior of Two Perlidae Species (Insecta, Plecoptera) in a River in Southern Spain

AbstractTwo Perlidae species, Dinocras cephalotes and Perla bipunctata, were studied in a river in Spain with the objectives of: a) describing their diets; b) detecting differences between size classes; c) analyzing niche breadth; and d) assessing the degree of niche overlap between both species and size classes. Dinocras cephalotes and Perla bipunctata nymphs fed mainly on Baetidae and immature Chironomidae. We did not detect significant differences in the quantity of ingested detritus, algae, and leaf pieces. Niche breadth was very low, although both species presented a high niche overlap. P. bipunctata seems to select some prey items throughout its nymphal development, whereas D. cephalotes augments its diet with other prey items as it grows. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Bioavailability and biodegradation of nonylphenol in sediment determined with chemical and bioanalysis

The surfactant nonylphenol (NP) is an endocrine-disrupting compound that is widely spread throughout the environment. Although environmental risk assessments are based on total NP concentrations, only the bioavailable fraction possess an environmental risk. The present study describes the bioavailability and biodegradability of NP over time in contaminated river sediment of a tributary of the Ebro River in Spain. The bioavailable fraction was collected with Tenax TA(R) beads, and biodegradation was determined in aerobic batch experiments. The presence of NP was analyzed chemically using gas chromatography-mass spectrometry and indirectly as estrogenic potency using an in vitro reporter gene assay (ER(alpha)-luc assay). Of the total extractable NP in the sediment, 95%+/-1.5% (mean +/- standard error) desorbed quickly into the water phase. By aerobic biodegradation, the total extractable NP concentration and the estrogenic activity were reduced by 97%+/-0.5% and 94%+/-2%, respectively. The easily biodegradable fraction equals the potential bioavailable fraction. Only 43 to 86% of the estrogenic activity in the total extractable fraction, as detected in the ER(alpha)-luc assay, could be explained by the present NP concentration. This indicates that other estrogenic compounds were present and that their bioavailability and aerobic degradation were similar to that of NP. Therefore, we propose to use NP as an indicator compound to monitor estrogenicity of this Ebro River sediment. To what extent this conclusion holds for other river sediments depends on the composition of the contaminants and/or the nature of these sediments and requires further testing.

Robert White: A River in Spain: Discovering the Duero Valley in Old Castile. London and New York: I.B. Tauris Publishers. 1998. 192 pp. $18.95

A refreshingly unique travel guide, A River in Spain: Discovering the Duero Valley in Old Castile, invites us to think differently about the way we prepare for and conduct our activities as travelers. Spain’s Duero River valley, mostly overlooked by travelers, is a region of magnificent visual beauty and significant historic interest.

A Social Analysis of the Bioinvasions of Dreissena polymorpha in Spain and Hydrilla verticillata in Guatemala

Human agency plays a key role in the processes of biological invasions. This comprises not only the human role in the configuration of driving forces or in the perception of the impacts, but also the conceptualization of alien species themselves as an environmental problem. This paper examines different stakeholders' positions in bioinvasion processes at different scales, and it looks at their relevance for the management of invasive species. It compares two cases: the invasion process of Dreissena polymorpha in the Ebro River in Spain and the case of Hydrilla verticillata in Lake Izabal, Guatemala. Our results are structured according to impacts and to management options. The discussion focuses on the relevance of incorporating the different stakeholders' interests and values in the analysis and management of biological invasions. Although social analysis of stakeholders' positions is necessary in order to foster management actions, it also reveals conflicts on the relevant criteria and on the very definition of invasive species.

The Role of Thiol Species in the Hypertolerance of Aspergillus sp. P37 to Arsenic

Aspergillus sp. P37 is an arsenate-hypertolerant fungus isolated from a river in Spain with a long history of contamination with metals. This strain is able to grow in the presence of 0.2 M arsenate, i.e. 20-fold higher than the reference strain, Aspergillus nidulans TS1. Although Aspergillus sp. P37 reduces As(V) to As(III), which is slowly pumped out of the cell, the measured efflux of oxyanions is insufficient to explain the high tolerance levels of this strain. To gain an insight into this paradox, the accumulation of acid-soluble thiol species in Aspergillus sp. P37 when exposed to arsenic was compared with that of the arsenic-sensitive A. nidulans TS1 strain. Increasing levels of arsenic in the medium did not diminish the intracellular pool of reduced glutathione in Aspergillus sp. P37, in sharp contrast with the decline of glutathione in A. nidulans under the same conditions. Furthermore, concentrations of arsenic that were inhibitory for the sensitive A. nidulans strain (e.g. 50 mM and above) provoked a massive formation of vacuoles filled with thiol species. Because the major fraction of the cellular arsenic was present as the glutathione conjugate As(GS)3, it is plausible that the arsenic-hypertolerant phenotype of Aspergillus sp. P37 is in part due to an enhanced capacity to maintain a large intracellular glutathione pool under conditions of arsenic exposure and to sequester As(GS)3 in vacuoles. High pressure liquid chromatography analysis of cell extracts revealed that the contact of Aspergillus sp. P37 (but not A. nidulans) with high arsenic concentrations (> or =150 mM) induced the production of small quantities of a distinct thiol species indistinguishable from plant phytochelatin-2. Yet, we argue that phytochelatins do not explain arsenic resistance in Aspergillus, and we advocate the role of As(GS)3 complexes in arsenic detoxification.

Entropy inference of recurrence models for variability analysis of extreme events

A complete methodology is developed to analyze the recurrence of extreme environmental events and its variability as time without further events elapses. Firstly we investigate the conditioned recurrence inference problem consisting in the selection of a probability model for the interarrival time between extreme events, given a contexto-factual evidence conditioned by the time elapsed since the last of such events. Two ways to include this condition can be considered, which yield alternative conditioned evidences and convert the former problem into two distinct ones, thus giving rise to a possible consistency violation. These problems are formalized within the logical probability framework, in a plausible logic language that allows a suitable expression of the available observational data. They are solved using the REF relative entropy method with fractile constraints, and their solutions are compared at all inference levels. It is concluded that the two conditioning ways are not really mutually exclusive and that a unique global solution to the conditioned inference can be obtained using this procedure. An example illustrates an application of the methodology to the variability analysis of the recurrence time between historical inundations of the Guadalquivir river in Spain, as time elapses with no new floods.

High-Speed Railway Bridge over the Ebro River, Spain

The new railway bridge over the Ebro river in Spain that carries the high-speed line from Madrid through Zaragoza to the French border is described. The 546 m total span is divided into two areas: a 162 m approach span and the 384 m span over the river. The Vierendeel girder has a total depth of 9.15 m and a trapezoidal cross-section. The approach span has the same bottom slab as the main span. The construction process involved incremental launching from both abutments. The box girder is prestressed both longitudinally and transversely. The bridge has 12 trapezoidal piers. The bridge is characterized by circular voids in the walls and an intermediate structural behaviour between that of an open U-shaped cross section and a closed box girder cross section. Details are given of the structural analysis, construction process and costs. Details are given of the owner, designer, contractor and service date.

Testing the limits of biological tolerance to arsenic in a fungus isolated from the River Tinto.

The Tinto river in Spain, with its high acidity and heavy metal concentrations (As, Cu, Cr, Zn), is an example of an environment hostile to life. Yet despite these extreme conditions, the site possesses a great diversity of eukaryotic life forms. We report the isolation of a filamentous fungus able to grow at 200 mM arsenic ( approximately 15 000 p.p.m.), i.e. a concentration 20-fold above that withstood by the reference microorganisms Escherichia coli, Saccharomyces cerevisiae and Aspergillus nidulans, and 200 times greater than that tolerated by Aspergillus niger. Based on morphological, physiological and genotypic criteria, the strain belongs to the genus Aspergillus. High concentrations of the metalloid induced vacuolation, suggesting that this organelle is someway connected to arsenic tolerance. Concentrations that are lethal to other organisms do not stress Aspergillus sp. P37. The fungus was capable of removing arsenic from culture media. In addition to arsenic hyper-resistance, it also displayed a polyresistant phenotype to copper and chromium.

Microbiology: eukaryotic diversity in Spain's River of Fire.

The Rio Tinto, known by the Phoenicians as 'Ur-yero', or 'River of Fire', because of its deep red colour and high acidity, flows through the world's largest pyritic belt in southwestern Spain. Surprisingly, eukaryotic microbes are the principal contributors of biomass in this hostile river, which has a pH of 2 and contains much higher concentrations of heavy metals than are typically found in fresh waters. Here we show that the Rio Tinto shows an unexpected degree of eukaryotic diversity and includes new lineages that we have identified by sequence analysis of genes encoding small-subunit ribosomal RNAs. The diversity of these eukaryotes is much greater than that of prokaryotes, whose metabolism is responsible for the extreme environment.

Fluvial Landscapes, Catchment Administration and Land-use Planning: experience based on two rivers in Spain

The differences between urban, rural and fluvial landscapes pose challenges for land-use planning. In particular, the stable character of urban settlements and cultural landscapes contrasts with the instability of fluvial ones. In Spain, the administration of fluvial landscapes, via the main legal instrument (the Hydraulic Public Domain) and land-use plans, is conducted on the basis of administrative boundaries which cut across hydrological units. The characteristics and dynamics of fluvial landscapes (in particular two Spanish rivers) are studied and it is argued that land uses established within them should be compatible with their characteristics and dynamics. In order to implement this objective, two new concepts are proposed for adoption by the river agencies and for incorporation in local land-use plans—the Area of Fluvial Freedom and the Area of Flooding.

Fluvial Landscapes, Catchment Administration and Land-use Planning: Experience based on two rivers in Spain

The differences between urban, rural and fluvial landscapes pose challenges for land-use planning. In particular, the stable character of urban settlements and cultural landscapes contrasts with the instability of fluvial ones. In Spain, the administration of fluvial landscapes, via the main legal instrument (the Hydraulic Public Domain) and land-use plans, is conducted on the basis of administrative boundaries which cut across hydrological units. The characteristics and dynamics of fluvial landscapes (in particular two Spanish rivers) are studied and it is argued that land uses established within them should be compatible with their characteristics and dynamics. In order to implement this objective, two new concepts are proposed for adoption by the river agencies and for incorporation in local land-use plans—the Area of Fluvial Freedom and the Area of Flooding.

Geomorphological and sedimentological features in Quaternary fluvial systems affected by solution-induced subsidence (Ebro Basin, NE-Spain)

The Quaternary evolution and the morpho-sedimentary features of some of the most important rivers in Spain (Ebro and Tagus rivers among others) have been controlled by subsidence due to alluvial karstification of the evaporitic bedrock. The subsidence mechanism may range from catastrophic collapse to slow sagging of the alluvium by passive bending. In the Ebro Basin, the mechanisms and processes involved in karstic subsidence were studied through the analysis of present-day closed depressions as well as through old subsidence depressions (palaeocollapses and solution-induced basins) and associated deformations recorded in the Quaternary alluvial sediments. The Gállego–Ebro river system is presented as a case study of channel adjustments and geomorphic and sedimentary evolution of fluvial systems in dissolution-induced subsidence areas. In this fluvial system, evaporite dissolution during particular Quaternary time intervals (namely early and middle Pleistocene) have lead to the development of a solution-induced basin, approximately 30 km-long by 8 km-wide, filled by Quaternary deposits with a total thickness in excess of 190 m. The main river response to balance the subsidence in the alluvial plain was aggradation in the central reach of the subsiding area, and degradation both in the upstream reach and in the valley sides where alluvial fans and covered pediments may prograde over the fluvial sediments. The main sinking areas are recognized in the sedimentary record by anomalous thickenings in the alluvial deposits and fine-grained sediments deposited in backswamp and ponded areas.

<i>Margaritifera auricularia</i> (Unionoidea, Margaritiferidae), the giant freshwater pearl mussel rediscovered in Spain

Margaritifera auricularia was described by Spengler in 1793. Since then specimens have been found in several localities in Western Europe and North Africa, often as fossils. However no living specimens have been scientifically recorded since 1917 (Haas, 1917). This author was the only one to study live specimens, collected in the Ebro River in Spain, publishing a short paper about its anatomy (Haas, 1924). As no more specimens were ever found, no data exist about its reproductive habits, spawning season nor is there a description of its larval stages. In a recent survey of Spanish Rivers to inventory the Habitats Directive (Directive 92/43/CEE) non-insect invertebrate species (Ramos, 1998), we found living populations of this giant pearl mussel in a very ancient channel (Imperial Canal) of the Ebro River (Araujo & Ramos, 1996) and in the Ebro (Alvarez Halcon, 1998), both in Aragon. More recently, there has been news about other M. auricularia populations living in the lower course of the Ebro river and in one of its irrigation channels (Altaba, 1997), both in Catalonia. An interesting theory exists about the specificity between M. auricularia and the Western European sturgeon Accipenser sturio (Linnaeus, 1758), a relict fish in European rivers and extinct in Spain. Both species occur together in Pleistocene deposits (Preece, 1988) and both have been declining since the first half of this century. With this theory in mind, we introduced several sturgeons into an aquarium with mussels, realizing that all mussels began to spawn. In the aquarium the mussels released all their larval stages, from unfertilized eggs to mature glochidia, passing through all intermediate stages. The glochidium of M. auricularia is very small (about 140 microns) and presents very small teeth. It is of the hookless type, as in other known species of the genus (Araujo & Ramos, 1998). This kind of glochidium specifically attaches itself to the gill filaments of the fish, whereas the hooked ones, typical of other genera, also attach themselves to the fins. Inmediately after the glochidia were released, we observed how they attached to the fish gills. We excised the gill filaments of the sturgeons 1, 2, 3, 4, 5 hours and 2, 3, 5, 13, 34 and 60 days after the begining of glochidia release. Now we are studying histological and scanning samples of these gill filaments in order to investigate the encystment process and to discover the period the glochidia need to complet their metamorphosis. Timing and length of the glochidial release period in the wild has been determined by collecting drift samples. With these data, fish were collected by electrofishing in order to investigate their susceptibility to the glochidia. The large size of all the specimens from the Imperial Canal population and the longevity achieved by species of this genus (around 100 years) suggest that this population may not have reproduced for many years. This leads us to ask wether the species has lost its reproductive capability, if it is unable to complete larval maturation or do the juveniles simply have a different habitat that we have not been able to find up to now? In situ observations suggest that the species should be more common, as occurs with other related genera (i. e. Unio, Psilunio, Anodonta) in the study area, if any kind of fish were compatible with

A River in Spain

A River in Spain