Guadiana River Research Articles

Automatic Detection of Aquatic Weeds: A Case Study in the Guadiana River, Spain

The spread of aquatic invasive plants is a major concern in several zones of the world's geography. These plants, which are not part of the natural ecosystem, cause a negative impact to the environment, as well as to economy and society. In Spain, large areas of Guadiana (the second longest river in Spain) have been invaded by such plants. Among the strategies to address this problem, monitoring and detection play an important role to control the spatio-temporal distribution of the invasive plants. The main objective of this work is to develop a methodology able to automatically detect the geo-location of aquatic invasive plants using remote sensing and machine learning techniques. To this end, several classification algorithms have been applied to freely available multispectral satellite imagery, collected by ESA's Sentinel-2 satellite. A quantitative and comparative assessment is conducted using different machine and deep learning algorithms, from classical methods such as unsupervised K-means to supervised random forests (RFs) and convolutional neural networks (CNNs). This study also proposes a methodology for validating the obtained classification results, generating synthetic ground truth images based on available high spatial resolution imagery. The obtained results demonstrate the suitability of some of the considered algorithms for automatic detection of aquatic weeds in satellite images with medium spatial resolution.

Holm oak wood pastures in SE Portugal: a spatial and temporal multiscale approach

Montados are oak wood-pastures occupying 11% of the Portuguese territory. This agroforestry system has been traditionally used for animal husbandry, agricultural, and forestry purposes. Present day Montados are threatened by land use changes, either intensification or abandonment, and climate global warming that has fostered parasitic plagues and enhanced hydric stress. This study highlights the relevance of holm oak (Quercus rotundifolia) wood-pastures in SE Portugal’s landscape throughout the last 125 years and assesses its health condition for the last two decades aiming to evaluate the chances of its continuity. Spatially, we use the Portuguese territory on the left bank of the Guadiana river for the historical changes on land use, and 6 farmlands located within this region to analyse present day tendencies. Temporally, we consider the intervals 1890–2015 and 2006–2019. We analysed five land use maps from different dates using ArcGIS to access holm oak Montados’ areas in the different dates to analyse its variation over time. We used Google Earth’s images to evaluate the present-day tendencies in tree density and mortality. Results indicate that holm oak woodland distribution in the study area increased during the twentieth century having maintained quite stable from the 1990’s to the present day. However, a negative trend in tree density during the latter period was found. We also verified that tree natural regeneration is not enough to replace dying trees hinting towards a conversion of grazed woodlands into treeless pastures, concluding that if these tendencies persist the continuity of the holm oak agroforestry system in south-eastern Portugal may be threatened.

Basketry as an ecosystem service of wetlands: traditional crafts in central Spain

Ecosystem services from wetlands include products such as food, water, fibers, timber, medicinal plants, and genetic resources for agriculture. One of the most abundant supplies is the raw material for basketry. In this study we aim to document the role of wetland plants as resources for basketry and broom-making in the Guadiana river basin and to analyze the local traditional knowledge of the species used in the area. We describe different types of baskets and other artifacts, and document basketry techniques. We found 30 species belonging to 12 families, 18 of them occurring in wetlands, four in irrigated fields, and seven in the adjacent dry territories. Twenty species are used in the manufacture of brooms. Twenty two types of basketry artifacts are described with their uses. The area shows a relevant cultural heritage, not merely as it was in the past, but also adapted to the new cultural and social contexts. The degradation and loss of wetlands in central Spain threatens these ecosystems and their associated cultural heritage. We suggest the declaration of this intangible human heritage as the “Culture of the Mediterranean Wetlands” before it disappears.

8. Western Europe

Editorial note: Due to unforeseen circumstances, we were unable to include the 2019 report in last year’s volume, and, for that reason, it is included here. 2019 Report On 8 January, the Portuguese Republic deposited its instrument of accession to the 2001 International Convention on the Control of Harmful Anti-fouling Systems on Ships. Entry into force occurred on 8 April. Two main issues remain critical for international river basins: water quantity and quality. Minimum water flows delivered by Spanish dams, although in compliance with the 1998 Convention on the Co-operation for the Protection and Sustainable Use of the Water Resources of the Portuguese–Spanish River Basins (Albufeira Convention), do not qualify as adequate from an ecological water flow perspective. Poor water quality reaching the international border remains a serious problem, especially in the Tagus and Guadiana river basins. During the summer of this year,...

Bioactive Compounds in Sarcocornia and Arthrocnemum, Two Wild Halophilic Genera from the Iberian Peninsula.

(1) Background: this study describes bioactive compounds in the following halophytes: Sarcocornia (S. alpini, S. pruinosa, and S. perennis) and Arthrocnemum (A. macrostachyum). The material comes from: coastal marshes in Tinto River, Guadiana River, and some interior provinces from the Iberian Peninsula. (2) Methods: the techniques used were Folin–Ciocalteu, GC-MS, and ESI-MS/MS. (3) Results: Five phenolic acids were found in Sarcocornia: trans-cinnamic, salicylic, veratric, coumaric, and caffeic acids. In addition, in Arthronemum, ferulic acid was also detected. The obtained flavonoids were cyanidin-3-O-arabinoside, luteolin-7-glucoside, dihydroquercetin, and p-coumaroyl-glucoside. They also presented fatty acids, such as palmitic, linoleic, and oleic acids in Sarcocornia, while palmitic, linolenic, and stearic acids were the main fatty acids in A. macrostachyum. (4) Conclusions: the high diversity of the compounds identified confirms the relation between nutritional interest and salt tolerance in halophytes.

The catastrophic floods in the Guadiana River basin since 1500 CE

The task of retrieving information about past flood events is very important to reconstruct flood series data. In this work, a wide range of different sources including newspapers, technical reports, and books was consulted in order to recover information about catastrophic flood events in Badajoz (Spain). A set of 37 catastrophic floods of the Guadiana River that occurred in Badajoz in the winter months (DJFM - December, January, February, and March) have been recovered since 1500 CE. This strong seasonality constrain is due to the important influence of the large-scale circulation patterns in winter affecting the climate of the Iberian Peninsula. Moreover, it is found that there is a clear difference between a higher number of floods in the 19th and 20th centuries and a substantial lower value of floods in the 16th–18th centuries. Finally, we evaluated the long-term evolution and inter-annual variability of the precipitation and the main large-scale atmospheric circulation patterns that govern climate variability in Iberia (NAO and EA modes) for the period 1851–1985. This analysis suggests that most extreme floods observed in this period (26 events) correspond to consecutive months with higher than usual precipitation, driven in part by unusual values of both the NAO and the EA modes of variability.

Aragonite saturation state in a continental shelf (Gulf of Cádiz, SW Iberian Peninsula): Evidences of acidification in the coastal area

The spatiotemporal variability of aragonite saturation state (ΩAr) has been studied in the eastern shelf of the Gulf of Cádiz (GoC) (SW Iberian Peninsula). The study was carried out during the years 2014 and 2016 aboard twelve oceanographic cruises, along three or five transects, located between Cape Trafalgar and the Guadiana River. The GoC exhibited oversaturated of calcium carbonate with ΩAr mean values of 2.68 ± 0.30 in surface and 2.05 ± 0.15 in deep waters. pH, total alkalinity (TA), calcium concentration (Ca2+) and ΩAr showed a high variability within the surface mixed layer (SML, z < 100 m). Biological activity seemed to be the main process to determine the ΩAr variability in the SML, revealing a greater importance than temperature, mixing or air-sea processes. The buffer factors of the CO2 system in the GoC have been estimated in the SML waters, and they are related with the biological activity and the temperature changes. A decrease of pH and ΩAr in this SML with depth was observed, due to the increase of the respiratory processes. In deep waters (z > 100 m), TA and Ca2+ concentration presented a conservative behaviour related to the distribution of the different water masses located in the GoC. The vertical variation of ΩAr also depends on the degree of mineralization of these water masses, obtaining the maximum values in the Subtropical North Atlantic Central Water (100–200 m), minimum values in the Subpolar North Atlantic Central Water (about 400 m), and intermediate values associated to the presence of the Mediterranean Water (>500 m). Results showed a significative acidification of the coastal areas, for those depths lower than 100 m from 2006 to 2016, with a mean decrease of pH and ΩAr of −0.0089 and −0.0552 yr−1, respectively.

Numerical reconstruction of historical extreme floods: The Guadiana event of 1876

In recent decades, the development of numerical tools has facilitated the ability to reproduce extreme flood events, which allows a far better understanding of their features, contributing to mitigate their negative effects in similar future scenarios. This paper analyzes the flood event that occurred in December 1876 in Badajoz (Spain-Guadiana basin), one of the most catastrophic flood events recorded in Europe, using a three-stage methodology. First, an estimation of the precipitation recorded in the Guadiana river basin during the days prior to the event was carried out starting from the precipitation data recorded in two precipitation stations located in the western part of the basin; second, Guadiana river flow in Badajoz was obtained by means of the HEC-HMS code using the precipitation estimated in the first stage. Third, the flood registered on December 1876 in Badajoz was reproduced using the numerical code Iber+. The peak flow obtained was equal to: 12,774 ± 1,360 m3s−1. This value improves the accuracy of estimated shown in previous works which, most of them, are lower limits of this value. Numerical results of the flood event in Badajoz and in areas surrounding the city show a good agreement with water marks and some descriptions of the event found in the literature. Results obtained in this work demonstrate the ability of the methodology to reproduce historical extreme flood events even when the availability of input data is relatively scarce.

Effects of sea level rise on salinity and tidal flooding patterns in the Guadiana Estuary

Abstract Sea level rise is a worldwide concern as a high percentage of the population is located in coastal areas. The focus of this study is the impact of sea level rise in the Guadiana Estuary, an estuary in the Iberian Peninsula formed at the interface of the Guadiana River and the Gulf of Cadiz. Estuaries will be impacted by sea level rise as these transitional environments host highly diverse and complex marine ecosystems. The major consequences of sea level rise are the intrusion of salt from the sea into fresh water and an increase in flooding area. As the physical, chemical, and biological components of estuaries are sensitive to changes in salinity, the purpose of this study is to further evaluate salt intrusion in the Guadiana Estuary caused by sea level rise. Hydrodynamics of the Guadiana Estuary were simulated in a two-dimensional numerical model with the MOHID water modeling system. A previously developed hydrodynamic model was implemented to further examine changes in salinity distribution in the estuary in response to sea level rise. Varying tidal amplitudes, freshwater discharge from the Guadiana River and bathymetries of the estuary were incorporated in the model to fully evaluate the impacts of sea level rise on salinity distribution and flooding areas of the estuary. Results show an overall increase in salinity and land inundation in the estuary in response to sea level rise.

¿Y los campesinos dónde están? Una propuesta de análisis para el estudio del campesinado y su aplicación en el valle medio del Guadiana durante la I Edad del Hierro

El campesinado es quizás una de las figuras sociales menos analizadas en la protohistoria peninsular por el escaso reflejo que su actividad deja en el registro arqueológico. Para contribuir a su conocimiento se propone un esquema de trabajo que reúne la información procedente de las actuaciones arqueológicas, los análisis bioarqueológicos y los estudios de las Áreas de Captación Económica. Dicho esquema ha sido aplicado al estudio de los asentamientos tipo aldea o granja documentados en el tramo medio del Guadiana entre los siglos VII-V a.C. para ensayar su utilidad y así comprender el papel que el campesinado pudo desempeñar en el desarrollo social y económico del poblamiento de esta región durante la I Edad del Hierro.

Anatomía Hidráulica de los Ojos del Guadiana (I)

&lt;p class="Cuerponormal"&gt;El Río Guadiana nacía gracias al caudal sobrante del acuífero manchego occidental, recurso que era aprovechado en sus primeros cincuenta kilómetros por dieciséis molinos hidráulicos. Este conjunto industrial perduró hasta la segunda mitad del pasado siglo, cuando distintas obras de drenaje y desecación junto al agotamiento del acuífero, provocaron un yermo panorama donde agua y vida imperaron durante siglos. El primer objetivo de esta investigación independiente, desarrollada en la sección de humedales del CREA y en la Escuela de Caminos de la UCLM, es caracterizar el sistema hidráulico original a través de geo-historiografía y trabajos de campo integrados en un sistema de información geográfica, con el objeto de simular su hidrodinámica prístina con el modelo IBER bajo condiciones de avenida. Los resultados permitirán estimar la capacidad de carga hidráulica y de laminación de avenidas de los dieciséis azudes y molinos en operación en el siglo XVI, que servirán de escenario base para analizar el impacto de las obras de drenaje venideras. Estos parámetros son esenciales en cualquier proyecto de restauración fluvial orientado a recuperar el dominio público hidráulico histórico y mitigar los potenciales efectos del cambio climático.&lt;/p&gt;

WINE CULTURAL LANDSCAPE AND VERNACULAR TYPOLOGIES IN SOUTH-WESTERN IBERIA: THREE CASE STUDIES IN ALENTEJO AND ANDALUSIA

Abstract. In the Mediterranean scenery of the south-western Iberian Peninsula, vineyards and wine-making have consistently been key pieces of the man-made cultural landscape, influencing urban design and even housing. This paper compares wine production influence in the cities of Borba, in Portuguese Alentejo, Jerez de la Frontera and Bollullos Par del Condado, in Spanish Andalusia, throughout the spheres of territorial organization, urban layout, presence of production buildings inside urban areas, and winemaker and wineworker housing. The study is based on architectonic surveys of building types: wineries, dwellings and houses with integrated wine production on both sides of the Guadiana River. The information gathered in surveys is complemented with data from historical documents, such as transaction records from the 16th to the 19th centuries. The research analyses cycles of prosperity for the three case studies – which are often coincident and related, within the frame of pre-industrial global trade – and the effects of those in winery and housing typologies. Across the studied area, vernacular winery types adhere to the same two categories, or typological lines, of building: the domestic winery and the autonomous building. Wine related architecture is still a key asset in these cities' material and cultural heritage, as it provides scale and uniqueness to the urban and rural ensembles, despite the fact that wine production has been removed from cities’ centres to outer industrial wineries. The memory of wine-induced prosperity is imprinted on the cities’ physical realities, giving meaning to their collective memories and proving to be an asset to future development.

Temporal variability of flooding events of Guadiana River (Iberian Peninsula) during the middle to late Holocene: Imprints in the shallow-marine sediment record

Sedimentological, geochemical and benthic foraminiferal proxies were used to interpret changes of depositional environments in a mud entrapment inside the Guadiana River paleo-valley, northern Gulf of Cadiz, to understand the temporal variability of fluvial flooding events and to detect patterns of latitudinal climatic variability in western Iberia.The period between ca. 5800 and ca. 1250 cal yr BP was characterized by slowly accumulating coarse-grained sediments, high content of biogenic sand components, and high abundances of shallow-water benthic foraminiferal species. After ca. 1250 cal yr BP, the sedimentary environment was dominated by fine-grained sediments, with high abundances of opportunistic benthic foraminiferal species and successful colonizers, and high values of geochemical ratios indicative of enhanced terrigenous supply. Sedimentation rates increased drastically over the last ca. 500 years.The genesis of these environments was mainly driven by the variable frequency of fluvial flooding events driven by the regional climate variability. Low terrigenous sediment input under dry conditions prevailed in the older sedimentary unit. Flood frequency and terrigenous sediment supply increased during the younger unit. The variability of the North Atlantic Oscillation at centennial scales highly influenced the sediment supply during the last ca. 500 years, with high terrigenous supply during negative NAO conditions. Our results corroborate an N-S gradient along the Atlantic Iberia during middle and late Holocene, with more humid conditions in the northwestern and drier conditions towards the southeast. The gradient weakened over the past ca. 500 years, with increased rainfalls and flood events during the Little Ice Age.

Estuarine Mapping and Eco-Geomorphological Characterization for Potential Application in Conservation and Management: Three Study Cases along the Iberian Coast

Geomorphological changes in recent decades in three estuaries along the Iberian coast were analysed using aerial orthophotographs. A hierarchical classification scheme, based on a literature review representing 26 estuarine eco-geomorphological features relevant to estuarine dynamics and functioning, is described. The estuaries selected were San Vicente de la Barquera (N Spain), Guadiana River (SW border between Spain and Portugal) and the Ebro River Delta mouth (NE Spain). For these systems, a 60-year time series of high-resolution maps was developed, analysing the changes in feature surfaces. The main subsystems analysed were beach, dunes, saltmarshes and the drainage network. The results of the cartographies showed general behaviour common to all transitional systems, relationships among main subsystems and processes inherent to each one. This work illustrates how beaches and dunes serve as a protective barrier for the tidal flats, acting as a sediment buffer for the entire system. The subsystems are connected by the drainage network responsible for the exchange of matter and energy between them. Furthermore, an accuracy assessment was performed in one of the study zones to identify the limitations of mapping with aerial photographs. The results explain the changes with time but also the processes and relationships between the estuarine features at a long-term scale. This work adds an important perspective towards a general understanding of their dependence on intrinsic and boundary conditions.

The Effects of High River Discharges on the Morphodynamics of the Guadiana ebb-tidal delta

López-Ruiz, A.; Garel, E., and Ferreira, Ó., 2020. The effects of high river discharges on the morphodynamics of the Guadiana ebb-tidal delta. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 558-562. Coconut Creek (Florida), ISSN 0749-0208.This work analyses the role of high river discharges upon the morphodynamics of an ebb-tidal delta at a jettied inlet (the Guadiana river mouth, at the southern border between Portugal and Spain). The analysis is performed using a numerical model to simulate the effects of synthetic single high river discharge events with return periods ranging from 3 to 670 years. This model was calibrated and validated both for hydro- and morphodynamics. Results show that the area with mobile sediment over the delta varies strongly with the magnitude of the river discharge. Events peaking over 7,500 m3/s produce significant bathymetric variations at the delta, including scouring of the inlet channel, along with the offshore migration and volumetric growth of the outer shoal. Observations have indicated that the delta does not recover from these sudden morphological changes. However, the recent strong river flow regulation by dams has limited the maximum river discharges to 2,500 m3/s. Such vanishing of unusually high discharge events has affected both the short-term and long-term morphodynamics of the Guadiana ebb-tidal delta.

La Extremadura musulmana (1142-1248). Organización defensiva y sociedad

L'Extrémadure almohade se configure dans la partie occidentale de la péninsule à la façon d'une avancée musulmane. Le Tajo délimite norma­lement, pendant tout ce période, la frontière entre les musulmans et les chrétiens, après la conquête définitive de Coria par Alphonse VII. De cette façon, l'Extrémadure musulmàne devient un authentique repère frontalière, même si elle ne présente pas un profit homogène. La zone qui correspond au versant méridional du Tajo possède un caractère tout à fait défensif (il n'apparait que des forteresses mais aucun village) et possiblement avait une population et une activité économique peu abondante. Des lieux comme Cáceres, facilement conquis par Geraldo Sempavor, deviennent inexpugna­bles, grâce à l'activité constructive almohade. La vallée du Guadiana main­tient une certaine continuité dans sa structure économique, d'apres les abon­ndants villages, ainsi qu'une importante activité agraire. Il s'établie, donc, une dichotomie entre une première zone entièrement frontalière et une deu­xième que nous pouvons dénommer, dans un sens rélatif, d'arrière-garde. Les almohades ne passent pas de représenter en Extrémadure une concep­tion simplement défensive et jamais ils n'ont conçu la fortification du lieu comme une étape dans la récupération de la Transierra chrétienne.

Comparing performance indicators to characterize the water supply to the demands of the Guadiana River basin (Spain)

ABSTRACT Water indicators and indices are useful tools to assess river basin performance, that is, to measure whether the basin operates satisfactorily under a wide range of possible future demands and hydrological conditions. Spanish regulations assess the performance of water demands by using reliability indicators (RIs), established by law in 2008. This article raises the possibility of updating RIs by comparing them with sustainability indicators (SIs). SIs are widely used for the assessment of river basin performance and several policy scenarios. We applied a water allocation model to the Guadiana River basin in Spain to compare indicators under three scenarios. The study was framed within the science of socio-hydrology, combining the physical environment of a water system with its influence on social aspects. SIs gave better results than RIs when comparing future scenarios. We also propose the introduction of a vulnerability indicator into Spanish regulations.

Drought and Ecological Flows in the Lower Guadiana River Basin (Southwest Iberian Peninsula)

Drought temporal characterization is a fundamental instrument in water resource management and planning of basins with dry-summer Mediterranean climate and with a significant seasonal and interannual variability of precipitation regime. This is the case for the Lower Guadiana Basin, where the river is the border between Spain and Portugal (Algarve-Baixo Alentejo-Andalucía Euroregion). For this transboundary basin, a description and evaluation of hydrological drought events was made using the Standardized Precipitation Index (SPI) with monthly precipitation time series of Spanish and Portuguese climatic stations in the study area. The results showed the occurrence of global cycles of about 25–30 years with predominance of moderate and severe drought events. It was observed that the current requirements of ecological flows in strategic water bodies were not satisfied in some months of October to April of years characterized by severe drought events occurring in the period from 1946 to 2015. Therefore, the characterization of the ecological status of the temporary streams that were predominant in this basin should be a priority in the next hydrologic plans in order to identify the relationships between actual flow regimes and habitat attributes, thereby improving environmental flows assessments, which will enable integrated water resource management.

Temporal and Spatial Variations of Secchi Depth and Diffuse Attenuation Coefficient from Sentinel-2 MSI over a Large Reservoir

The Alqueva reservoir (South of Portugal) in the Guadiana river basin constitutes the most important water resource in southern Portugal for domestic and agricultural consumption. We present a methodology developed to characterize spatial and temporal variations of Secchi depth and diffuse attenuation coefficient (both related to dissolved/suspended particles and to water transparency), using high spatial resolution satellite images from Sentinel-2 Multi-Spectral Instrument (MSI). Empirical relations between satellite retrievals of surface reflectances and in situ measurements of water parameters were defined and applied to the entire reservoir for spatial and temporal analysis in the period July 2017–June 2019, useful in the identification of microalgae blooms and rapid variations in water characteristics, which allowed us to differentiate five zones. Water estimates with lower transparency and higher attenuation of radiation were found in the northern area of Alqueva reservoir during the months characterized by higher water temperatures, with Secchi depth monthly averages near 1.0 m and diffuse attenuation coefficient near or above 1.5 m-1. Satellite retrievals of water with greater transparency in the reservoir were obtained in the southern area in months with low water temperature and atmospheric stability, presenting some monthly Secchi depth averages above 3 m, and diffuse attenuation coefficient below 0.8 m-1. January 2018 presented great transparency of water with a Secchi depth of 7.5 m for pixels representing the 95th percentile and diffuse attenuation coefficient of 0.36 m for pixels representing the 5th percentile in the Southern region.

Characteristics of organic matter sources from Guadiana Estuary salt marsh sediments (SW Iberian Peninsula)

Estuaries are dynamic interfaces between land, rivers and the ocean that play major roles in the global carbon cycle. These coastal wetlands store huge amounts of organic carbon (OC), commonly known as “blue carbon” and excellent places to study C cycling. The Guadiana river estuary is among the most important tidal salt marshes in the South - Iberian coastal margin. Here, a detailed organic geochemical study is described that includes the identification of sedimentary OM composition at a molecular and isotopic level. Total organic carbon content (TOC) of core sediments ranged from 0.39 to 2.23% and stable carbon isotope composition (δ13C) also showed a wide range between −22.4 and −27.0‰. A13C depletion trend observed from the surface to bottom in the core sediments profiles, reflects loss of labile biogenic 13C enriched compounds i.e. polysaccharides and a selective preservation of more depleted compounds with depth i.e. lignin and lipids in the core sediments. Series of n-alkanes were found in the range from C10 to C31. Carbon preference index ratio (CPI) calculated for long-chain n-alkanes (C24–C31) that ranged between 1.17 and 1.94 reflecting diverse OM inputs to the sediments. A study of the lignin-derived phenolic composition pointed to a recalcitrant OM derived from both gymnosperm and angiosperm plants. Moreover, high abundance of vinyl phenol and vinyl guaiacol points to a dominant contribution of lignins from grasses and aquatic macrophytes to the sediments. A well-resolved series of long-chain linear alkyl benzenes (LABs from C4 to C22) were recorded in all core sediment samples indicating direct discharge of untreated domestic and/or industrial effluents to the estuary. Polycyclic aromatic hydrocarbons (PAHs) with more than 3 rings reflects the pyrogenic origin of a portion of the sedimentary OM. This study highlights the importance of different OM sources to the lower Guadiana estuarine sediments and contributes to a better knowledge about its origin, dynamics and fate.