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Nowadays, the Mediterranean freshwater systems face the threat of water scarcity, along with multiple other stressors (e.g., organic and inorganic contamination, geomorphological alterations, invasive species), leading to the impairment of their ecosystem services. All these stressors have been speeding up, due to climate variability and land cover/land use changes, turning them into a big challenge for the water management plans. The present study analyses the physicochemical and phytoplankton biomass (chlorophyll-a) dynamics of a large reservoir, in the Mediterranean region (Alqueva reservoir, Southern Portugal), under diverse meteorological conditions and land cover/land use real scenarios (2017 and 2018). The most important stressors were identified and the necessary tools and information for a more effective management plan were provided. Changes in these parameters were further related to the observed variations in the meteorological conditions and in the land cover/land use. The increase in nutrients and ions in the water column, and of potentially toxic metals in the sediment, were more obvious in periods of severe drought. Further, the enhancement of nutrients concentrations, potentially caused by the intensification of agricultural activities, may indicate an increased risk of water eutrophication. The results highlight that a holistic approach is essential for a better water resources management strategy.

Nowadays, the Mediterranean freshwater systems face the threat of water scarcity, along with multiple other stressors (e.g., organic and inorganic contamination, geomorphological alterations, invasive species), leading to the impairment of their ecosystem services. All these stressors have been speeding up, due to climate variability and land cover/land use changes, turning them into a big challenge for the water management plans. The present study analyses the physicochemical and phytoplankton biomass (chlorophyll-a) dynamics of a large reservoir, in the Mediterranean region (Alqueva reservoir, Southern Portugal), under diverse meteorological conditions and land cover/land use real scenarios (2017 and 2018). The most important stressors were identified and the necessary tools and information for a more effective management plan were provided. Changes in these parameters were further related to the observed variations in the meteorological conditions and in the land cover/land use. The increase in nutrients and ions in the water column, and of potentially toxic metals in the sediment, were more obvious in periods of severe drought. Further, the enhancement of nutrients concentrations, potentially caused by the intensification of agricultural activities, may indicate an increased risk of water eutrophication. The results highlight that a holistic approach is essential for a better water resources management strategy info:eu-repo/semantics/publishedVersion

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.

The Guadiana Basin.(SW Iberian Peninsula) is affected by acid mine drainage (AMD), a consequence of ancient mining activities in the Iberian Pyrite Belt (IPB). Consequently, the sedimerits at the Alqueva reservoir (SE Portugal) in the Guadiana Basin are potentially contaminated by trace elements, which make important: (i) to characterize the status of trace element pollution of the sediments; (ii) to evaluate the mobility and the bioavailability of As, Cd, Cu, Cr, Pb and Zn; and (iii) to assess the environmental risk associated with the total and bioavailable concentrations of trace elements, using the sediment quality guidelines (SQGs) and the risk assessment code (RAC). Metal enrichment factors (EF) and geoaccumulation indexes (I-geo), determined taking into account the regional background levels, revealed that, among the metals analyzed, Cd contributed the highest to pollution levels followed by Pb and As. Despite the trace element contamination of the Alqueva sediments, the sequential extraction showed that Most of them are found in the oxidizable and residual fractions, which indicates that they are sparingly bioavailable, with exception of Cd (acid-labile fraction) and Pb (reducible fraction). Based on the RAC, Cd was the only metal that presented a high risk, while Pb, As and Zn showed a medium risk. Moreover, the SQGs revealed the existence of certain areas of extremely high risk, particularly related to high concentrations of total As and, in less extent, of Pb and Cd, associated with AMD, wastewater discharges and runoff of plant protection products from agricultural fields located near the reservoir. (C) 2015 Elsevier By. All rights reserved. FCT (Fundacao para a Ciencia e Tecnologia) [PTDC/AAC-AMB/103547/2008]; FEDER, through POFC (Eixo I - Programa Operacional Fatores de Competitividade) from QREN [COMPETE Re: FCOMP-01-0124-FEDER-008582] info:eu-repo/semantics/publishedVersion

Freshwater reservoirs can be impacted by several hazardous substances through inputs from agricultural activity, sewage discharges, and groundwater leaching and runoff. The water quality assessment is very important for implementation of the monitoring and remediation programs to minimize the risk promoted by hazardous substances in aquatic ecosystems. Evaluation of the degree of contamination of aquatic environments must not take in account only its chemical characterization but it must be complemented with biological assays, which determine potential toxic effects and allows an integrated evaluation of its effects in populations and aquatic ecosystem communities. The application of this type of strategy has clear advantages allowing a general evaluation of the effects from all the water components, including those due to unknown substances and synergic, antagonistic, or additive effects. There are only a few studies that reported ecotoxicological acute end points, for the assessment of surface water quality, and the relationship among toxicity results and the anthropogenic pollution sources and the seasonal period. The aim of this study was to assess the ecotoxicological characterization of the surface water from Alqueva reservoir (South of Portugal) and to evaluate the influence of anthropogenic sources of pollution and their seasonal variation in its toxicity. The construction of Alqueva reservoir was recently finished (2002) and, to our knowledge, an ecotoxicological assessment of its surface water has not been performed. Because of that, no information is available on the possible impact of pollutants on the biota. The surface water toxicity was assessed using acute and chronic bioassays. The results are to be used for developing a monitoring program, including biological methods. Water samples were collected during 2006-2007, at each of the nine sampling sites selected in Alqueva reservoir. These sampling points allow an assessment at the upstream (Sra. Ajuda, Alcarrache, Alamos-Capta double dagger o), at the middle (Alqueva-Montante, Alqueva-Mouro, Lucefecit), and at the downstream of the water line (Alqueva-Jusante; Ardila-confluncia; Moinho das Barcas). The campaigns occurred in February, March, May, July, September, and November of 2006 and February, March, and May of 2007. The rainy season comprised November, February, and March, and the dry season included May, July, and September. A total of 81 samples were collected during the study period. The physical-chemical parameters were analyzed following standard and recommended methods of analysis (APHA et al. 1998). The pesticide analyses were performed using gas chromatography according to DIN EN ISO 6468 (1996). Surface water ecotoxicity was evaluated using the following bioassays: Vibrio fischeri luminescence inhibition, Thamnocephalus platyurus mortality, and Daphnia magna immobilization and reproduction assay. The Spearman rank correlation coefficients were used to evaluate the associations between the water sample physicochemical properties (from each sampling station in each season) and the acute and chronic toxicological effects, with a level of significance p < 0.05. In the acute toxicity study, the species that was found to be the most sensitive was T. platyurus. T. platyurus detected a higher number of toxic water samples during the dry season. Concerning the luminescent inhibition of V. fischeri, the results showed that this organism detected a great number of toxic water samples in rainy seasons. The water samples, which promoted higher toxic effects towards this species, were from the north and from the middle of the reservoir. The correlation analysis showed that V. fischeri luminescent inhibition (%) was positively correlated with total phosphorus, chlorpyrifos, iron, and arsenic. T. platyurus mortality (%) was positively correlated with the water pH, 5-day biochemical oxygen demand (BOD(5)), chlorides, atrazine, simazine, terbuthylazine, and endosulfan sulfate contents. Although the surface waters did not promote acute toxicity to the crustacean D. magna, in the chronic exposure, a significant decrease in the number of juveniles per female was observed, mainly at the dry period. The number of juveniles per female, in the reproduction test of D. magna, was negatively correlated with pH, temperature, BOD(5), chloride, atrazine, simazine, terbuthylazine, and endosulfan sulfate. The water toxicity of the Alqueva water might be due principally to the intensive agriculture activities surrounding the reservoir and to the municipal wastewater discharges. The physicochemical parameters and the pesticide concentrations indicated that the water quality was worse in the north part of the reservoir system. These results are characteristic of the majority of reservoirs, once the construction of the dam promoted, by itself, the impounding of water flow and the increase of compound residence time. The toxicity tests corroborate with the chemical characterization. Acute toxicity of Alqueva water may be a result of the effect promoted by chlorpyrifos, endosulfan sulfate, phosphorus, and iron. Chronic toxicity may be a result of the effect of herbicides, arsenic, organic matter, endosulfan sulfate in mixture. Hence, the water toxicity of the Alqueva might be due principally to the intensive agriculture activities surrounding the reservoir and to the municipal wastewater discharges. This study has shown that a large number of samples from different sites of the Alqueva reservoir contained potentially toxic contaminants. The sites with impaired water quality were those located at the north of the reservoir and in the surrounding areas of intensive agricultural activity. The results demonstrated that the use of a screening of acute and chronic toxicity tests with organisms from different trophic levels and with distinct sensibilities allowed the detections of several patterns of toxicity from spatial and temporal variability promoted by natural or anthropogenic sources. The chronic responses showed, especially in the dry season, that some of the species belonging to this aquatic ecosystem might be at risk. The V. fischeri and T. platyurus are two species that should be used in the acute bioassays for the ecotoxicological monitoring programs of this reservoir. It is recommended that other species, such as a productive organism (algae), be included in the next study, once the water reservoir had high levels of herbicides. Ecotoxicological assessment of surface water must integrate initial screening based on acute tests followed always by chronic bioassays. The results implicitly suggest that the implementation of processes of remediation by reducing pollutant input into the reservoir and by the implementation of water treatment processes is important and necessary.

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The apparatus exploited in this work is composed of an optical cable linked to a portable FieldSpec UV/VNIR that records the spectral downwelling radiance in underwater environment, allowing us to calculate the shortwave attenuation coefficient in water. Results for three inland water bodies are presented under different atmospheric conditions (sun zenith angle and wind speed) and water composition (chlorophyll α concentration and turbidity). We show that the spectral downwelling zenith radiance profiles under high sun elevations present a positive slope in the upper layers due to relatively high scattering of direct sunlight compared to attenuation. For deeper layers, attenuation overcomes the scattering of sunlight leading to a constant negative logarithmic slope. For low sun elevations, a negative slope is observed in the entire water column since the scattering of direct sunlight is always lower than attenuation. Whenever a negative logarithmic constant slope is observed, the attenuation coefficient was computed. A relation was observed between attenuation coefficient in the photosynthetically active radiation (PAR) spectral region and water turbidity, for the three water bodies under study. Keywords: apparatus, spectroradiometer, inland water, underwater radiance profiles, attenuation coefficient (Published: 6 November 2013) Citation: Tellus A 2013, 65 , 20774, http://dx.doi.org/10.3402/tellusa.v65i0.20774 This publication is part of a Thematic Cluster entitled "Parameterization of lakes in numerical weather prediction and climate models". Read the other papers from this thematic cluster here

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Tese de doutoramento em Engenharia Civil, Eutrophication is a serious environmental problem in lakes and reservoirs worldwide. The eutrophic Alqueva reservoir (Portugal) is the largest western European reservoir and constitutes a vital regional water resource. The river Guadiana, which is the main tributary to the Alqueva reservoir, imports large nutrient loads leading to eutrophication being an issue in this waterbody. But despite its importance and problems, few scientific studies concerning the Alqueva exist. This work aims at contributing to foster the understanding of water ecology in the Alqueva reservoir through the use of data analysis techniques and numerical modelling. The results contained herein can be used to assist management decisions in this waterbody and the modelling effort can be used to obtain forecasts in this and other reservoirs and improve understanding of ecological behavior there. Data analysis methods, namely time series analysis, were applied to monitoring data collected between 2003-2009 at several locations and depths in the Alqueva reservoir in order to infer possible spatial and temporal patterns. The monitoring data comprised climatology, hydrology and water quality data from different sources. Data analysis showed that the Alqueva behavior presents high interannual variability. This is mainly a consequence of the high variability of precipitation, nutrient loads and Guadiana hydrological regimen. It was found that the system is P-limited and that nutrients input is mostly dependent on the main tributary input loads. Therefore management schemes aimed at improving the trophic level in the Alqueva should focus on reducing phosphorus in the Guadiana inflow. Numerical modelling main goals were to develop and apply tools to simulate the main ecological traits in the Alqueva reservoir. A new numerical model to simulate eutrophication processes in lakes and reservoirs based on a hybrid deterministic-stochastic approach was developed. A plain methodology to estimate nutrient loads in a basin was also developed. These tools were used together with the finite element based hydrodynamic model RMA-10 to perform simulations of currents, thermal structure and eutrophication in the Alqueva reservoir. The models were successfully calibrated and validated in both two-dimensional and three-dimensional versions. Model performance was assessed by comparing simulation results with in situ measured data. It was found that the models reproduced Alqueva thermal structure quite accurately and eutrophication related trends reasonably well. The performance of the eutrophication tool was constrained by the availability and quality of input and forcing data. It was shown that the particular geomorphological and hydrological characteristics of the reservoir together with local climate features are responsible for the existence of two distinct ecological regions within the reservoir whose boundary can be placed at a transect south of monitoring station 3: - The upper part of the reservoir is a shallow channel like region with riverine characteristics that is interrupted by a few scattered deeper pools. This area receives the major nutrients input and is eutrophic. Hydrodynamic in this area is governed by hydraulically induced currents from the Guadiana. - The lower part of the reservoir is a deep lacustrine area that presents stable thermal and oxygen stratification in summer (April – October). In this region, wind induced currents and thermal stratification are the dominant hydrodynamic traits. Wind is dominant over hydraulic flow during all year and affects mostly the surface circulation. Model results indicate that the velocities in the reservoir are always smaller than 0.25 m/s, with the higher values occurring in the upper reservoir area. The Alqueva was found to present a monomictic behavior with a seasonal summer stratification that is responsible for generating anoxic bottom waters during dry season. An autumnal overturn leads to a fully mixed water column in winter season. Model findings, corroborated by data, indicate that phytoplankton in the Alqueva peaks in spring and in autumn with productivity in the upper reservoir area presenting values much higher than in the lower part. Dry season ecology seems to be ruled by stratification while wet season ecology main driving force appears to be the nutrients load through the main tributary. The Alqueva was build to boost economic development in the region and provide irrigation water for agriculture activities. It can be inferred from the results of the present work that the major problem it may face is the impacts of the poor water quality coming from the Guadiana. The Guadiana river carries wastewater with a high level of nutrients from a large Spanish population, from industries and from agriculture activities. The development of effective water quality management in this reservoir should therefore focus on nutrient containment strategies for the Guadiana river inflow., A eutrofização constitui um sério problema ambiental em lagos e albufeiras. A albufeira de Alqueva (Portugal) é a maior albufeira da Europa ocidental e constitui um importante recurso aquático regional. O principal afluente de Alqueva, o rio Guadiana, introduz elevadas cargas de nutrientes na albufeira fazendo com que a eutrofização seja motivo de preocupação nesta albufeira. Apesar da sua importância e problemas, existem poucos estudos científicos sobre a albufeira de Alqueva. Este trabalho tem como objectivo contribuir para o conhecimento e compreensão da ecologia aquática na albufeira de Alqueva através do uso de análise de dados e modelação matemática. Os resultados obtidos podem ser utilizados na tomada de decisões de gestão nesta albufeira e o trabalho de modelação pode ser utilizado para efectuar previsões nesta ou noutras albufeiras ou lagos. Foram aplicados métodos de análise de dados, nomeadamente métodos de análise de séries temporais, a dados de campanhas de monitorização recolhidos no período 2003-2009 em diferentes pontos da albufeira de Alqueva para inferir da existência de padrões espaciais e temporais. Os dados de monitorização são oriundos de diferentes fontes e abrangem climatologia, hidrologia e qualidade da água A análise de dados permitiu concluir que a ecologia do Alqueva tem uma elevada variabilidade interanual que é consequência da elevada variabilidade da precipitação, cargas de nutrientes e regime hidrológico. Concluiu-se que o nutriente limitante é o fósforo e que a entrada de nutrientes no sistema depende sobretudo das cargas que entram pelo afluente principal. Donde resulta que uma gestão eficiente da melhoria do estado trófico da albufeira deve centrar-se na redução do fósforo nas afluências do Guadiana. Os principais objectivos da modelação foram desenvolver e aplicar ferramentas para simular as principais características ecológicas da albufeira de Alqueva. Desenvolveu-se um novo modelo matemático para simular a eutrofização em lagos e albufeiras baseado numa abordagem híbrida determinística-estocástica. Desenvolveu-se também uma metodologia simples para estimar cargas de nutrientes em bacias hidrográficas. Estes instrumentos foram utilizados em conjunto com o modelo hidrodinâmico RMA10, baseado no método dos elementos finitos, para simular correntes, estrutura térmica e eutrofização na albufeira de Alqueva. Os modelos foram calibrados e validados com sucesso nas versões tridimensional e bidimensional integrada lateralmente. O desempenho dos modelos foi avaliado por comparação entre os resultados de simulações e medidas experimentais realizadas in situ. Verificou-se que os modelos reproduzem com grande exactidão a estrutura térmica da albugeira de Alqueva e razoavelmente bem as variações relacionadas com a eutrofização. O desempenho do modelo de eutrofização foi condicionado pela disponibilidade e qualidade dos dados de entrada e de forçamento. Mostrou-se que as características geomorfológicas e hidrológicas particulares da albufeira, em conjunto com características climáticas locais, são responsáveis pela existência de duas zonas ecológicas distintas na albufeira, cuja fronteira se localiza a sul da estação de amostragem 3: - A parte superior da albufeira é uma região de leito linear com águas pouco profundas, interrompida a espaços por lagoas mais profundas, que tem características fluviais. Esta zona é muito eutrófica e por ela entram a maior parte dos nutrientes do sistema. A hidrodinâmica nesta área é governada por correntes induzidas pelo fluxo do Guadiana. - A parte inferior da albufeira é uma região lacustre profunda que apresenta estratificações térmica e de oxigénio estáveis durante o verão (Abril - Outubro). Nesta zona as características hidrodinâmicas dominantes são as correntes induzidas pelo vento e a estratificação térmica. O vento é dominante sobre o fluxo hidráulico durante todo o ano e afecta sobretudo a circulação à superfície. Os resultados da modelação indicam que as velocidades na albufeira são sempre inferiores a 0.25 m/s, com os maiores valores a ocorrer na parte superior da albufeira. Concluiu-se que a albufeira de Alqueva apresenta um comportamento monomíctico com uma estratificação sazonal de verão que é responsável pela geração de camadas de água anóxica no fundo da albufeira durante a estação seca. A circulação convectiva outonal dá origem a uma coluna de água completamente misturada na estação do inverno. Os resultados de modelação, corroborados por dados de campo, indicam que o fitoplâncton no Alqueva apresenta picos primaveris e outonais, com a produtividade na parte superior da albufeira a apresentar sempre valores muito superiores à da parte inferior. A ecologia da estação seca parece ser governada pela estratificação ao passo que a força motriz da ecologia da estação húmida aparenta ser a carga de nutrientes que entra através do afluente principal. A barragem de Alqueva foi construída para fomentar o desenvolvimento económico regional e fornecer água de irrigação para actividades agrícolas. Dos resultados obtidos neste trabalho pode-se concluir que o maior problema com que a albufeira se depara é os impactos da água de baixa qualidade que é trazida pelo rio Guadiana. O Guadiana transporta efluentes com um elevado nível de nutrientes provenientes de uma vasta população espanhola, de indústrias e de actividades agrícolas. Consequentemente, o desenvolvimento de uma gestão de qualidade da água eficaz nesta albufeira deve centrar-se em estratégias de remediação/contenção do fósforo trazido pelo Guadiana.

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Multivariate statistical techniques were applied to evaluate spatial/temporal variations, and to interpret water quality data set obtained at Alqueva reservoir (south of Portugal). The water quality was monitored at nine different sites, along the water line, over a period of 18 months (from January 2006 to May 2007) using 26 water quality parameters. The cluster analysis allowed the formation of five different similarity groups between sampling sites, reflecting differences on the water quality at different locations of the Alqueva reservoir system. The PCA/FA identified six varifactors, which were responsible for 64% of total variance in water quality data set. The principal parameters, which explained the variability of quality water, were total phosphorus, oxidability, iron, parameters that at high concentrations indicate pollution from anthropogenic sources, and herbicides indicative of an intensive agricultural activity. The spatial analysis showed that the water quality was worse in the north of the reservoir.

Surface waters located in intensive agricultural areas are more vulnerable to the pesticides contamination, which is a major concern if the water is intended to be used for human consumption. The aim of this study was to evaluate the presence and the distribution of pesticides in the Alqueva reservoir, an important source of water supply (South of Portugal), considering their representativeness in the agricultural practice of the area. For the analysis of pesticides risk impact we used the environmental quality standards in the field of water policy proposed recently by the European Commission. The pesticides belonging to the classes of phenylureas, triazines, chloroacetanilides, organophosphorous and thiocarbamates were analysed by on-line solid phase extraction-liquid chromatography-tandem mass spectrometry. The pesticides more frequently detected were atrazine, simazine, diuron and terbuthylazine. The highest levels of these pesticides were registered in spring, after pesticides treatment, namely in olive-tree and vine crops. The priority pesticides atrazine and diuron reached values above the annual average proposed in the European Union Legislation. The herbicide atrazine reached values that surpassed the proposed maximum allowable concentration (2 000 ng L−1). The sampling stations most affected by these pesticides were Sra. Ajuda, Lucefecit and Alcarrache, located in the northern part of the reservoir, closer to Spain where the agricultural activity is more intensive. Keywords: Surface water quality, Pesticides, Alqueva reservoir, On-line solid phase extraction-liquid chromatography-tandem mass spectrometry, Principal component analysis, Environmental quality standards levels

Se hace referencia a la primera captura de la lucioperca Sander lucioperca (Linnaeus, 1758) en el embalse de Alqueva (cuenca del Guadiana, suroeste de la Península Ibérica). Los ejemplares, de entre dos y tres años, fueron capturados entre agosto y octubre de 2008 con trasmallos. Se aportan datos morfométricos y merístcos de los mismos (n = 9) The pikeperch Sander lucioperca (Linnaeus, 1758) is recorded for the first time in the Alqueva Reservoir (Guadiana River Basin, SW Iberian Peninsula). Fish were captured with trammel nets from August to October 2008. The age of specimens was comprised between two and three years old. Morphometric and meristic characteristics of specimens (n = 9) are reported

This study aims to assess the physico-chemical variability of the Alqueva reservoir during its initial filling period. The dataset consists of analytical results from an 11 month survey (Mar 2003-Jan 2004) conducted in the water body, at three levels of depth in the several tributaries and in the discharge section. 21 parameters were monitored on a monthly base, in order to understand the temporal and spatial variability. Another goal of this work was to use a multivariate statistical approach to help understand the relationships between water quality parameters, to group zones according to their similarities and to distinguish between wet and dry season conditions. FA/PCA needs 6 VF/PC to point out 74 % in the wet season, and 7 VF/PC to explain 78.6 % of variance in the dry season. FA/PCA allows grouping the selected parameters according to common features. As a result, mineral content is indicated as the principal source of variability in the wet season, while oxygenation plays the main role in the dry season. DA renders an important data reduction using 10 parameters to provide 93.2 %right assignations during temporal analysis. DA assigns temporal variability to the consequences of water balance on ambient salinities, to stratification influences and to surface runoff. Also, it uses only 4 parameters to yield 71.3 % right assignations during the spatial analysis in the dry season. Conductivity declines in the lacustrine zone, while CBO5, pH and Temperature vary principally in the vertical sense. However, such a spatial pattern is not static. It can become either more defined during the dry season, or less evident during the expansion of the lotic conditions in the rainy period (late spring and summer). Seasonal processes of stratification/mixture determine the temporal changes in the lacustrine zone. The system seems to be affected by periodic apulses of modifications produced by intensive rains and drought. Thus, limnological understanding of these questions is a prerequisite for making wise judgments about reservoir management. Este estudio apunta a determinar la variabilidad fisco-química del embalse de Alqueva en su período de llenado inicial. El conjunto de datos consiste en resultados analíticos a partir de los primeros once meses de muestreo (marzo de 2003-enero de 2004) conducida en el cuerpo del agua, en tres niveles de profundidad; en los varios tributarios y en la sección de la descarga. 21 parámetros se han supervisado en una base mensual, para entender la variabilidad temporal y espacial. Otra meta de este trabajo fue el utilizar un acercamiento estadístico multivariado para ayudar a entender las relaciones entre los parámetros de la calidad del agua; para agrupar zonas según sus semejanzas y distinguir entre las condiciones de las estaciones húmeda y seca. FA/PCA necesita 6 VF/PC para precisar 74 % de la estación húmeda, y 7 VF/PC para explicar 78.6 % de la variación en la estación seca. FA/PCA permite agrupar los parámetros seleccionados seg'un características comunes. Como resultado el contenido mineral se señala como la fuente principal de la variabilidad en la estación húmeda, mientras que la oxigenación desempeña el papel principal en la estación seca. DA rinde una reducción de datos importante usando 10 parámetros para producir 93.2 % de clasificaciones correctas durante análisis temporal. DA asigna variabilidad temporal a las consecuencias del balance del agua en salinidades, a las influencias de la estratificación y a la salida superficial. Ademas, utiliza solamente 4 parámetros para rendir 71.3 % clasificaciones correctas durante el análisis espacial en la estación seca. La conductividad decae en la zona lacustre, mientras que CBO5, el pH y la temperatura varían principalmente en el sentido vertical. Sin embargo, un patrón tan espacial no es estático. Puede hacerse mas definido durante la estación seca, o menos evidente durante la expansion de las condiciones loticas en el período lluvioso (fin de primavera y verano). Los procesos estacionales de la mezcla de la estratificación determinan los cambios temporales en la zona lacustre. El sistema parece afectado por pulsos periódicos de las modificaciones producidas por las lluvias intensivas y sequía. Así la comprensión limnologica de estas preguntas es un requisito previo para hacer juicios sabios sobre la gerencia del embalse.