Maria manuela Portela

• Associate Professor with Aggregation
• Professor (Associate) at Technical University of Lisbon

This study examines exceptional maximum temperature (Tmax) events in mainland Portugal (1980–2024) using ERA5-Land reanalysis data at 1012 locations. To assess changes in the occurrence and temperature excess of exceptional events across two 22-year subperiods (or phases), percentile-based thresholds were adopted. An inventive severity heatmap is u...

This study explores the application of Temporal Fusion Transformers (TFTs) to improve the predictability of hourly potential hydropower production for a small run–of–the–river hydropower plant in Portugal. Accurate hourly power forecasts are essential for optimizing participation in the spot electricity market, where deviations incur penalties. Thi...

This study examines the trends in heatwave characteristics across mainland Portugal from 1980/1981 to 2022/2023, utilising ERA5-Land reanalysis data. To achieve this, the study applies the Heatwave Magnitude Index (HWMI) to identify heatwave days for minimum (Tmin) and maximum (Tmax) temperatures across 15 grid-points representing Portugal’s divers...

This study investigates the trends and characteristics of heatwaves in mainland Portugal from 1980/1981 to 2022/2023 using ERA5-Land reanalysis data. This research uses the Heatwave Magnitude Index (HWMI) to identify heatwave days for minimum (Tmin) and maximum (Tmax) temperatures across 15 grid-points representing Portugal’s diverse geography and...

Intense rainfalls and debris floods are familiar occurrences in Madeira Island (Portugal); but, understanding how intense rainfall relates to this type of floods is limited. This research seeks to characterise extreme rainfall events measured at the Funchal rain gauge station and to analyse their relationship with the region’s debris flood records....

This research examines the intricate changes in the number of occurrences and cumulative rainfall of exceptional events in Portugal spanning 42 hydrological years (from 1981/1982 to 2022/2023). The study has two primary objectives: assessing the hydrological spatial dynamics of a region susceptible to climate-induced variations in exceptional rainf...

Hydropower can have significant impacts on riverine ecosystems due to hydropeaking (i.e., artificial rapid and short-term fluctuations in water flow and water levels downstream and upstream of hydropower stations) that negatively affect downstream fish. However, when it comes to analyzing species habitat use and availability above and below small h...

Droughts are among the major natural hazards that are spreading to many parts of the world, with huge multi-dimensional impacts. An extensive analysis of drought phenomenon is presented for continental Croatia based on a meteorological E-OBS gridded dataset (0.25° × 0.25°), within the period of 1950–2022. The drought events were characterized by th...

In this research, heatwaves in Portugal were analysed using high-resolution daily minimum and maximum temperature data (Tmin and Tmax) from the European Reanalysis of Global Climate Observations (ERA5-Land) for the period from 1 October 1980 to 30 September 2021 (41 hydrological years) at four differentiated climatological locations in the country....

Droughts are among the major natural hazards that are spreading to many parts of the world with huge multi-dimensional impacts. For Continental Croatia an extensive analysis of drought phenomenon is presented based on meteorological E-OBS gridded dataset (0.25° x 0.25°), within the period of 1950 to 2022. The drought events were characterized by th...

This study presents a comprehensive analysis of heatwaves in mainland Portugal from 1 October 1980 to 30 September 2021 (41 hydrological years). It addresses a research gap by providing an updated assessment using high-resolution reanalysis daily minimum and maximum temperature data (Tmin and Tmax) from the gridded ERA5-Land dataset, overcoming the...

The Technical University in Kosice has the ambition to be a leader not only in the field of education, science and research but also in the care of the environment. The campus of the Technical University in Kosice near the city centre could be an example of a live sponge with many positive effects on people. With the planned project of restoring th...

This paper summarises an updated climate change trends analysis—developed for the period from 1 October 1864 to 30 September 2021 within the scope of a Horizon 2020-funded project to increase climate resilience in European coastal cities—for a representative site of the Lisbon Metropolitan Area (Portugal). By using long ground-based daily records o...

The need to increase hydropower production to reduce CO2 emissions, while supporting the development of self-sustainable fish populations in a cost-effective way, protect biodiversity and restore water-related ecosystems is urgent and recognized in the UN Agenda 2030 and in the recently launched European Green Deal. Despite the growing awareness of...

This paper describes the long-term grid-point rainfall trends in the context of climate change, recent regionalised rainfall decline and drought events for mainland Portugal, which is teleconnected, in most cases, to the trends of mathematical descriptions of the North Atlantic Oscillation (NAO) during the century from October 1919 to September 201...

O presente estudo estimou a pegada hídrica azul, verde e cinzenta dos principais produtos agrícolas da pauta de exportação do Estado do Ceará, no Semiárido Brasileiro, no período 1997 a 2012. Conclui-se que praticamente toda a água virtual exportada em produtos agrícolas pelo Ceará é proveniente da cadeia produtiva da castanha de caju, tanto pela g...

In hydrological modelling, a good result for the criterion of goodness of fit does not always imply that the hypothesis of mass conservation is fulfilled, and models can lose their essential physical soundness. We propose a way for detecting this anomaly by accounting the resulting water balance during model simulation and use it to modulate the ob...

Hydropeaking caused by small‐scale hydropower plants creates rapid changes in the intensity, frequency, and persistence of river flows. These changes can induce stress in fish across all life‐stages and, may negatively impact fish communities. Rapid increases in the flow velocity may cause fish to avoid unstable habitats, seeking out nearby refuges...

The water availability estimation in large regions is a relevant procedure to define broad water resources management policies but may prove difficult due to the lack of data and uncertainty to related regional hydrological and hydrogeological characterization. BALSEQ, a daily sequential water budget model, was applied in a set of twenty-two waters...

This paper explores practical applications of bivariate modelling via copulas of two likely dependent random variables, i.e., of the North Atlantic Oscillation (NAO) coupled with extreme rainfall on the small island of Madeira, Portugal. Madeira, due to its small size (∼740 km2), very pronounced mountain landscape, and location in the North Atlanti...

Changes in the rainfall amounts in a small island in the North Atlantic Ocean—Madeira Island—were analysed based on complete daily rainfall series aggregated into 1-, 3-, 6- and 12-month rainfall and annual maximum rainfalls of 41 rain gauges (1937/1938–2016/2017). The gaps of the daily rainfall data were filled in by the multivariate imputation by...

A partir de un total de 92 series de precipitación mensual de la base de datos de la Agencia Estatal de Meteorología (AEMET) se ha realizado un análisis exhaustivo de sequías en el marco espacial de la Demarcación Hidrográfica del Segura (DHS) y Mancomunidad de los Canales del Taibilla (MCT), organismos encargados de la planificación de los recurso...

The research presents a multisite annual streamflow generation model that combines the Generalized Linear Model (GLM), for determining the temporal structure, with copulas, for modelling the spatial dependence joint distributions. The performance of the GLM-Copula model was verified by comparing its ability to preserve historical features and simul...

The paper focuses on assessing the effects of floods on selected components of the environment in the Hornád river basin: the impact of floods on population, water conditions, soil, fauna, flora and their habitats, structure and use of land and landscape, protected areas and their protection zones, the territorial system of ecological stability, ur...

This study addresses the long-term rainfall trends, their temporal variability and uncertainty over mainland Portugal, a small country on the most western European coast. The study was based on monthly, seasonal and annual rainfall series spanning for a period of 106 years, between October 1913 and September 2019 (herein after referred to as global...

For improving sustainable water resources management and planning at local and regional scales, specifically in small islands, long-term and recent rainfall trends due to temporal shifts in major climatic drivers should be investigated based on dense and long-running ground data series — as done in this research work for the North Atlantic Portugue...

Extremal dependence or independence may occur among the components of univariate or bivariate random vectors. Assessing which asymptotic regime occurs and also its extent are crucial tasks when such vectors are used as statistical models for risk assessment in the field of Climatology under climate change conditions. Motivated by the poor resolutio...

Hydrologic processes, especially rainfall is characterized for their variability in time and space. These processes are known as stochastic processes. For engineering practice is very important to know the behavior of time series for long period. This paper is focused on spatial-temporal analysis of daily rainfall for Košice station in eastern Slov...

Extreme weather changes have been increasing in the recent times also in the eastern Slovakia. Extremely dry periods alternate with above-average precipitation. In the paper the drought indices were evaluated: Standardized Evapotranspiration Index (SPEI) and Standardized Precipitation Index (SPI). Using the non-parametric statistical Mann-Kendall t...

Downstream of small-scale hydropower plants (SHPs), the intensity, frequency and persistence of hydropeaking events often cause an intolerable stress on fish of all life stages. Rapid increases in flow velocity result in fish avoiding unstable habitats and seeking refuge to reduce energy expenditure. To understand fish movements and the habitat use...

Short-term heavy rains are one the most important rains from a meteorological, hydrological, and also technical point of view. When designing rainwater drainage systems or rainwater management systems, the intensity of short-term rains is used as a design parameter, because of short-term rains usually reach the highest intensity. This paper is focu...

The paper deals with the evaluation of meteorological droughts in eastern Slovakia. It is focused on description of method that is used to analyze and assess the river basin vulnerability through SPI index - standardized precipitation index (SPI). SPI index is applied for detecting dry and humid climate anomalies as well as could be used for charac...

The paper refers to a study on droughts in a small Portuguese Atlantic island, namely Madeira. The study aimed at addressing the problem of dependent drought events and at developing a copula-based bivariate cumulative distribution function for coupling drought duration and magnitude. The droughts were identified based on the Standardized Precipita...

Study region: Madeira Island, Portugal (a small island of the North Atlantic Ocean). Study focus: Droughts from January 1937 to December 2016, were studied using monthly rainfall at 41 rain gauges covering most of the island. The gaps of the original rainfall data were filled by Multiple Imputation by Chained Equations (MICE). The drought condition...

The standardized precipitation index (SPI), is one of the most used drought indices. However, it is difficult to use to monitor the ongoing drought characteristics because it cannot be expeditiously related to precipitation deficits. It also does not provide information regarding the drought probability nor the temporal evolution of the droughts. B...

The evidence about the climate change is now considered to be unequivocal. But if visible changes are occurring at an increased rate over shorter periods, then the time series of the hydrologic variables more directly related to the climate, as rainfall or temperature, should denote progressively more pronounced signs of such changes, under the for...

RESUMO: O modelo de gestão de recursos hídricos de uma região não é moldado unicamente pelos seus aspectos hidro climáticos; as tomadas de decisão são praticadas dentro de 'arranjos institucionais' locais-comportamento coletivo constitutivo do universo cultural. Assim, apesar das imensas semelhanças hidro climáticas das suas porções semiáridas, que...

Stream ow recession analysis characterizes the storage‐out ow relationship in catchments. This relationship, which typically follows a power law, summarizes all catchment‐scale subsurface hydrological processes and has long been known to be a key descriptor of the hydrologic response. In this paper, we tested a range of common recession analysis me...

The Intergovernmental Panel on Climate Change (IPCC) assessed with medium confidence that there has been an anthropogenic influence in the intensification of heavy rainfall at the global scale. Nevertheless, when taking into account gauge-based evidence, no clear climate-driven global change in the magnitude or frequency of floods has been identifi...

In this paper, the results of trend analysis applied to precipitation and temperature monthly data for the period from 1962 to 2014 is presented for the hydrological year (from November to October) in sixteen climatic stations in Eastern Slovakia. The topography of this part of the country is very diverse and it affects the climate. The Mann-Kendal...

This paper proposes a systematic assessment of the performance of an analytical modeling framework for streamflow probability distributions for a set of 25 Swiss catchments. These catchments show a wide range of hydroclimatic regimes, including namely snow-influenced streamflows. The model parameters are calculated from a spatially averaged gridded...

Many riparian ecosystems in Mediterranean Europe are affected by land use and flow alteration by dams. We focused on understanding how these stressors and their components affect riparian forests in the region. We asked the following questions: (1) Are there well‐defined, responsive riparian guilds? (2) Do dam‐induced streamflows determine abundanc...

Predicting extreme events is one of the major goals of streamflow forecasting, but models that are reliable under such conditions are hard to come by. This stems in part from the fact that, in many cases, calibration is based on recorded time series that do not comprise extreme events. The problem is particularly relevant in the case of data-driven...

The objective of this paper was to analyze the temporal and spatial trends in annual and seasonal precipitation in Slovakia utilizing 487 gauging station data collected statewide in the period from 1981 to 2013. The nonparametric Mann–Kendall (MK) statistical test, which has been widely used to assess the significance of trends in hydrological time...

This paper assesses the performance of an analytical modeling framework for streamflow probability distributions for summer streamflow of 26 Swiss catchments characterized by negligible anthropic influence. These catchments show a wide range of hydroclimatic regimes, including snow- and icemelt influenced streamflows. The model parameters are estim...

The objective of this study was to investigate rainfall trends in chosen climatic stations in Syria. Syria is prone to extreme climate events such as drought and flood. Annual as well as seasonal rainfall trends were detected by Mann-Kendall statistical test. The Sen’s slope was applied to identify the magnitude of those trends. The results achieve...

Resumo As séries sintéticas são de longa data utilizadas no âmbito da hidrologia, designadamente na análise de problemas ditos de natureza estocástica cujas soluções dependem dos valores do escoamento, mas também dos seus padrões temporais de ocorrência. A geração de séries sintéticas utiliza normalmente um de dois procedimentos: geração directa de...

In this paper we revisit the case study of Silva et al. (Stoch Env Res Risk A. doi:10.1007/s00477-015-1072-y, 2015), the Itajaí-açu River at Apiúna (Southern Brazil), with an augmented data set and Bayesian inferential techniques. Nonstationary Poisson-GP models are used to study the joint influence of El Niño-Southern Oscillation (ENSO) and of ups...

The aim of this study was to determine trends in gauging stations in Slovakia. We investigated 487 stations during the period 1981-2013. Monthly rainfall trends were detected by non-parametric Mann-Kendall statistical test. Precipitation trends show high variability. The precipitation time series in Slovakia in gauging stations in particular have a...

For many decades, synthetic streamflow series have been utilized in hydrology to analyze numerous stochastic problems whose solutions depend on the values of the streamflows and their temporal pattern. The stochastic generation of synthetic streamflows at a given time level can adopt two general approaches: the generation at the required time level...

An analytical model to quantify water resources in Alpine environments

Socioeconomic development often causes environmental and water related problems. Any solution requires knowledge, willingness and sufficient financial and technical means. Such capacity is limited in many developing and threshold countries. To identify opportunities for strengthening capacity in water and environmental management, we analysed Unive...

RESUMO: O presente artigo propõe um esquema, enquadrado no paradigma Bayesiano de inferência estatística, para a estimação de valores de projecto de precipitações máximas anuais com durações subdiárias. Tal esquema pretende combinar a informação contida em amostras, expectavelmente curtas, de registos subdiários da precipitação com informação resul...

O sucesso de uma estratégia de mitigação dos efeitos da seca passa pela implementação de um sistema de monitorização e previsão eficaz, capaz de identificar os eventos de seca e de seguir a sua evolução espácio-temporal. Neste artigo demonstrase a eficiência de redes neuronais artificiais na previsão, para Portugal, do índice de precipitação padron...

The objective of the present study is to characterize the drought occurrences in a region comprising Paraguay, southern Brazil and northeastern Argentina. To recognize the drought occurrences the standardized precipitation index at the time-scales of 3 and 6 months was applied to the rainfall records from 1961 to 2011 at 51 rain gauges located in t...

Flow duration curves for water resources quantification in Alpine environments

In its Energy Strategy 2050, Switzerland is revising its energy perspectives with a strong focus on renewable sources of energy and in particular hydropower. In this context, the Swiss Government funded a number of competence centers for energy research (SCCERs), including one on the Supply of Energy (SCCER-SoE), which develops fundamental research...

This paper discusses some aspects of flood frequency analysis using the peaks-over-threshold model with Poisson arrivals and generalized Pareto (GP) distributed peak magnitudes under nonstationarity, using climate covariates. The discussion topics were motivated by a case study on the influence of El Niño-Southern Oscillation on the flood regime in...

During the history of the Earth, numerous large-scale climate changes occurred, some of them with a cyclic nature. The majority of such changes happened in periods of hundreds, thousands or even millions of years as a result of natural causes, like small variations in Earth's orbit that change the amount of solar energy received by the planet. Howe...

Nowadays there seems to be a consensus among the scientific community that, due to climate change, there is an intensification of the hydrological cycle, which, coupled with evidence of the impact of persistent modes of regional climate variability, have led hydrologists to study hydrological extremes under nonstationarity. In this paper, the peaks-o...

Over the past decades, we have assisted to an increasing understanding of the effects of regulated-flow conditions on aquatic ecosystems. However, the responses to altered flows of the ecotonal ecosystems remain a long-standing chal-lenge in the Mediterranean regions. This is probably due to the multiple pressures that in-fluence directly and indir...

Rivers are presently experiencing dramatic changes in the stream flow regime by water di-version, river regulation, more extreme flood events and droughts, which reduce the capabil-ity of aquatic and stream-related ecosystems to adjust and absorb disturbances. The increas-ing pressures due to water needs and global changes (e.g. climate, land-use)...

Background & Aim: Alteration of flow regimes by dams causes shifts in the composition and diversity as well as the trait syndromes of streamside plant communities [1]. There is still a limited knowledge of riparian strategies to streamflow regulation and moreover to different dam operations. Such an understanding would enable us to more strategical...

The paper focuses on the development of the hydraulic–hydrological model used to simulate water resources management scenarios in the Zambezi River basin. The main challenges of the implementation of the model are the scarcity of continuous reliable discharge data and the significant influence of large floodplains. The Soil and Water Assessment Too...

Regional drought modes in Portugal are identified applying the Principal Component Analysis (PCA) and Varimax rotation to the Standardized Precipitation Index (SPI) computed on various time scales using the three precipitation datasets covering the period 1950–2003: (i) The observation dataset composed of 193 rain-gauges distributed almost uniforml...

The study presents an analysis of droughts using monthly rainfall data, from January 1961 to December 2011, from 11 rain gauges located in Paraguay and Northern Argentina. The characterization of the drought events used the standardized precipitation index (SPI) applied at different time scales (3, 6, and 12 consecutive months). The temporal variab...

The pattern-oriented memory (POM) is a novel historical rainfall interpolation method that explicitly takes into account the time dimension in order to interpolate areal rainfall maps. The method is based on the idea that rainfall patterns exist and can be identified over a certain area by means of non-linear regressions. Having been previously ben...

The aim of this paper is to test the ability of neural network approaches to hindcast the spring standardized precipitation index on a 6-month time scale (SPI6) in Portugal, based on winter large-scale climatic indices. For this purpose, the linkage of the spring SPI time series with the winter North Atlantic Oscillation (NAO) and the sea surface t...

This paper deals with the research of monthly precipitation trends in climatic stations in Libya and Slovakia. The non-parametric Mann-Kendall statistic test was applied to detect trends and to assess the significance of the trends in the time series. The evaluation was done for the time period from November to October. Trend analysis of rainfall d...