114 research outputs found
Morphological response of the saltmarsh habitats of the Guadiana estuary due to flow regulation and sea-level rise
In the context of rapid sea-level rise in the 21st century, the reduction of fluvial sediment supply due to the regulation of river discharge represents a major challenge for the management of estuarine ecosystems. Therefore, the present study aims to assess the cumulative impacts of the reduction of river discharge and projected sea-level rise on the morphological evolution of the Guadiana estuary during the 21st century. The assessment was based on a set of analytical solutions to simplified equations of tidal wave propagation in shallow waters and empirical knowledge of the system. As methods applied to estimate environmental flows do not take into consideration the fluvial discharge required to maintain saltmarsh habitats and the impact of sea-level rise, simulations were carried out for ten cases in terms of base river flow and sea-level rise so as to understand their sensitivity on the deepening of saltmarsh platforms.Results suggest saltmarsh habitats may not be affected severely in response to lower limit scenarios of sea-level rise and sedimentation. A similar behaviour can be expected even due to the upper limit scenarios until 2050, but with a significant submergence afterwards. In the case of the upper limit scenarios under scrutiny, there was a net erosion of sediment from the estuary. Multiplications of amplitudes of the base flow function by factors 1.5, 2, and 5 result in reduction of the estimated net eroded sediment volume by 25, 40, and 80%, respectively, with respect to the net eroded volume for observed river discharge. The results also indicate that defining the minimum environmental flow as a percentage of dry season flow (as done presently) should be updated to include the full spectrum of natural flows, incorporating temporal variability to better anticipate scenarios of sea-level rise during this century. As permanent submergence of intertidal habitats can be significant after 2050, due to the projected 79 cm rise of sea-level by the year 2100, a multi-dimensional approach should be adopted to mitigate the consequences of sea-level rise and strong flow regulations on the ecosystem of the Guadiana Estuary. (C) 2016 Elsevier Ltd. All rights reserved
Guadiana estuary: present state, past evolution and prospects for the future
The Guadiana catchment extends over an area of 66 889 km2, between the catchments of the Tagus and Guadalquivir rivers, of which 11 525 km2 are in Portugal. Its upper part in Spain corresponds to what is called the Western La Mancha province. To the North the watershed is limited by alignments, of the Sierra de Altomira http://www.castillalamancha.es/sites/default/files/documentos/paginas/archivos/altomira_liczepa_fich.pdf ) with heights between 700 and 1,000 meters and the Mancha de Toledo, with profusion of endorheic lagoons between 600 and 800 meters above sea level. The origin of the Guadiana was historically placed in the area of Campo de Montiel under the name Rio Pinilla.info:eu-repo/semantics/publishedVersio
Salt harvesting
Saltworks (other terms: salterns, saltponds, solar ponds) are man-made hypersaline systems where table salt or halite (NaCl, sodium chloride) is harvested. Salt production in the Guadiana River estuary is based on solar evaporation of sea water. In other areas, salt is obtained from solid state or brine mining.
Saltworks using sea water are usually located in low coastal areas, allowing gravitational filling of ponds during the high tides. Evaporative salt production is restricted to geographical areas where this process is favoured by combined action of wind, solar radiation, low rain rates, and high temperatures. Hence, the Mediterranean and part of the European Atlantic coastal areas fulfil these conditions, particularly during
the summer months where the evaporation greatly exceeds precipitation.info:eu-repo/semantics/publishedVersio
Sediment Imbalance Between Portuguese And Spanish Sectors Of Guadiana River Estuary
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv
The evolution of the European framework for coastal management, linked to the new environmental challenges. The Portuguese case
The sharing of space by various human activities leading to social conflicts and threats to ecosystems,
alongside increased awareness of the threats to coastal zones has created the need to legislate on coastal planning and integrated management by developing international guidelines. A new management challenge has emerged due to climate change that had not previously been considered in legislation or policies. Therefore, the European tools and frameworks applied in Portugal, their implementation and effectiveness will be analysed. Extensive bibliographic data was analysed including EU directives and policies, and Portuguese governmental documents from national to a municipal level. We found that all the European Union guidelines and frameworks are being implemented in the Portuguese Governmental planning and are very well substantiated, whereas the base of all land management instruments (IGT), have a questionable implementation, mainly due to the number of entities involved and the long implementation process.MACOMA SGA ERASMUS MUNDUS 2015-1626/001-001-EMJDinfo:eu-repo/semantics/publishedVersio
Organic carbon accumulation in coastal zones since the last glacial maximum? A clue for varying atmospheric CO2 levels?
It is a generally accepted concept that the carbon storage within the principal earth surface reservoirs varies in a multitude
of time scales. The shallow water continental margins belong to the most fertile areas in terms of organic carbon (OC)
production and are also very effective carbon traps
The material sources and processes during the infilling of estuaries in Algarve (South Portugal)
The actual estuary that occupies the Boina-Arade paleovalley
accommodated the Holocene sedimentary sequence
whose thickness does not exceed 35 m in the deepest zones,
as registered from geotechnical borehole data. We present here
the results of partial analyses of two continuous cores which
cross the Holocene sequence until the Pre-Quaternary
substratum. In the P5 core (Boina river), the sedimentary
column, which spans 20 m accumulated during ca 8500 years
Shore Platforms in the Algarve (South Portugal) Rocky Coast, an Inheritance of the Last Interglacial Stage?
Shore platforms, notches, and marine caves are common yet distinctive morphological
features along the southern coast of Portugal. The central Algarve rocky coast has provided a
favorable setting in which to understand the processes contributing to shore platform
development. This is because the morphology and characteristics of the features vary along
the coast, as do several factors implicated in their development such as wave climate
(including wave direction and frequency), seabed morphology and depth, bedrock lithology,
karstification and geological structure
Socio economic impacts of the guadiana jetty
The importance of beaches to the tourism industry and the need to protect such resources is
not only vital to the economy of nations but for many localities and regions. Coastal erosion is the major
reason of disappearance of beaches. As a result, it requires application of a series of engineering
techniques. Therefore, hard and soft engineering solutions are used for the shore protection and
utilization through recreational purposes. The Guadiana shore protection jetty Protugal and Spain border
represents a good example of such a problem. After the jetty was constructed, the west of the river
mouth, experienced a continuous trend of accretion, while the down drift sectors were subjected to severe
erosion. This jetty is a source of environmental problems and creates long term economic impacts in
positive and negative ways to the surrounding coast-line. The present study showed that, the Portuguese
side has gained more economic and social benefits, and conversely, the Spanish side has lost their
economic income and land due to the jetty construction
Características geoquímicas das margens dum estuário Atlanto-Mediterrânico (o Guadiana, Sudeste de Portugal): variação espacial e sazonal
The present work describes spatial and seasonal variability in grain-size, pH and elemental characteristics (TOC, TIC, TN and C/N) in
superficial sediments, as well as salinity, temperature and oxygen in the water, within the intertidal range of the Guadiana Estuary, SW Iberian
Peninsula, during the year 2010. The results indicate that environmental parameters in the estuary are strongly dependent on spatial patterns,
which reflect seasonal oscillations in freshwater discharge. The sediment is generally poorly sorted, with a symmetrical to very finely skewed
distribution, in accordance with the low-energy conditions typical of the deposition areas. During winter, heavy rains forced the continuous
discharge of Europe’s largest reservoir, the Alqueva dam, creating exceptional hydrodynamic conditions and causing coarser sediment deposition
in the estuary. High marsh areas are controlled by flood tides, promoting vertical accretion of muddy sediments, especially silts. The lower areas
of the saltmarsh and-mud flat areas are controlled by the ebb, with more efficient export of fines toward the platform and retention of sands,
sometimes with significant amounts of bioclasts. In winter (average Q = 654 m3 s
-1), salinity remained low throughout the estuary with the
highest values (< 3) recorded up to 3 km inland from the river mouth, except in the most confined environments subject to greater evaporation.
In summer (average Q = 52 m3 s
-1), the estuarine waters are better mixed and significant saltwater intrusion extends approximately 8 km inland.
The seasonal variation in surface water temperature was very high, with a difference of ca 14 º C in the maximum temperature recorded in
winter and summer.
A clear relationship between elevation (in relation to mean sea level) and organic matter, pH and particle size was observed. In the higher
areas of the marsh, where the hydrodynamics is attenuated, differential deposition of fine sediments promotes organic matter entrapment and
low pH. Sedimentary organic matter derives from a mixture of native aquatic and terrestrial sources. The mid-upper estuary areas and higher
zones of the saltmarsh in the lower estuary incorporate a greater terrestrial component, whereas the low-middle marsh areas of the lower estuary
experience a substantial contribution from indigenous aquatic sources.
The present data help to understand the present environmental condition of the Guadiana Estuary and contribute baseline data for future
climatic and environmental management studies based on sediment-dependent proxiesO presente estudo descreve a variabilidade espacial e sazonal das propriedades físico-químicas da água (salinidade, temperatura e
oxigénio) e dos sedimentos superficiais (granulometria, pH, COT, CIT, NT e C/N) da faixa intermareal do estuário do rio Guadiana, SW
da Península Ibérica durante o ano 2010. Os resultados indicam que as condições ambientais do estuário estão fortemente dependentes dos padrões espaciais e das oscilações sazonais na descarga de água doce. Os sedimentos apresentaram-se geralmente mal calibrados e com
uma assimetria tendencialmente fina, de acordo com as condições de baixa energia típicas de áreas de deposição. As fortes chuvas sentidas
durante o inverno forçaram a descarga contínua do maior reservatório artificial da Europa, o Alqueva, criando condições hidrodinâmicas
excecionais, promovendo o aumento de sedimentos grosseiros no estuário. A granulometria dos sedimentos ao longo da zona intertidal
tende a aumentar das zonas mais elevadas às zonas mais baixas. As zonas de sapal alto são controladas pela enchente, promovendo a
acreção vertical de sedimentos lodosos, sobretudo siltes. As zonas mais baixas do sapal e zonas de planície lodosa são controladas pela
vazante, com exportação mais eficiente de finos para a plataforma e retenção de areias, por vezes com conteúdo significativo em bioclastos.
No inverno (média Q = 654 m3 s
-1), a salinidade manteve-se baixa ao longo de todo o estuário, com os valores mais elevados (< 3)
registados até cerca de 3 km para montante a partir da foz do rio, exceto nos ambientes mais confinados, mais expostos à evaporação. No
verão (média Q = 52 m3 s
-1), as águas estuarinas apresentaram-se melhor misturadas e a intrusão salina estendeu-se até cerca de 8 km para
montante. A variação sazonal da temperatura das águas superficiais foi muito elevada, verificando-se uma diferença de ca 14ºC entre as
temperaturas máximas registadas no Inverno e no Verão.
No estuário, observou-se uma clara relação entre a elevação (relativa ao nível médio do mar) e a quantidade de matéria orgânica, o
tamanho do grão e o pH. Nas zonas mais elevadas do sapal, onde o hidrodinamismo é atenuado, a deposição diferencial de sedimentos
finos promove o aprisionamento de matéria orgânica e a diminuição do pH.
A matéria orgânica sedimentar deriva de uma mistura de matéria orgânica aquática e terrestre de origem autóctone. As zonas do
estuário médio-superior e as zonas mais elevadas do sapal do estuário inferior incorporam uma maior componente orgânica de origem
terrestre, enquanto que as áreas de baixo-médio sapal do estuário inferior experienciam uma contribuição substancial proveniente de
fontes aquáticas de origem alóctone.
A presente informação contribui para o melhor entendimento da atual condição ambiental do Estuário do Rio Guadiana e fornece
dados de base para futuros estudos de gestão ambiental e evolução climática que assentem em indicadores ambientais sedimentares.info:eu-repo/semantics/publishedVersio
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