N. Mamassis

National Technical University of Athens | NTUA · Department of Water Resources and Environmental Engineering

Ecosystems provide humanity with a wide variety and high economic value-added services, from biomass structuring to genetic information, pollutants' decomposition, water purification and climate regulation. The foundation of ecosystem services is the Eltonian Pyramid, where via prey-predator relationships, energy metabolism and biomass building tak...

In the context of implementing the European Flood Directive in Greece, a large set of rainfall data was compiled with the principal aim of constructing rainfall intensity–timescale–return period relationships for the entire country. This set included ground rainfall data as well as non-conventional data from reanalyses and satellites. Given the Eur...

Social structure is based on the availability of the Water-Energy-Food Nexus. To cover these needs of society, several solutions of different scales of infrastructures coexist. The construction of infrastructure is capital-intensive; therefore, investment risk is always a consideration. In this paper, we try to evaluate the investment risk by inter...

Water has always been a driver of human civilization. The first human civilizations thrived in places with an abundance of water, typically nearby large rivers as the Tigris–Euphrates, Yang Che and Nile. The invention and construction of hydraulic infrastructure came only later, in prehistoric times, triggered by the expansion of humanity in water-...

Τις τελευταίες δεκαετίες τα έργα υποδομής επεκτείνονται όλο και περισσότερο προς τις ορεινές και τις νησιωτικές περιοχές, με χαρακτηριστικό το παράδειγμα των έργων ανανεώσιμων πηγών ενέργειας (ΑΠΕ). Η επέκταση αυτή προκαλεί κοινωνικές αντιδράσεις, οι οποίες, μεταξύ άλλων, αποδίδονται και στις επιπτώσεις των έργων αυτών στο τοπίο. Στην παρούσα εργασ...

Hydroclimatic processes such as precipitation, temperature, wind speed and dew point are usually considered to be independent of each other. In this study, the cross−correlations between key hydrological−cycle processes are examined, initially by conducting statistical tests, then adding the impact of long−range dependence, which is shown to govern...

The newly excavated urban water supply system of the city of ancient Piraeus provides an excellent opportunity for the study and evaluation of the issues of sustainability, adaptability, simplicity and environmental protection, which are of main concern in modern engineering design practices. Well-digging in the area of Pireaus dates back to the ci...

Impacts to landscapes have been identified as major drivers of social opposition against renewable energy projects. We investigate how the process of mitigating landscape impacts can be improved and accelerated, through a re-conceptualization of visibility analysis. In their conventional format, visibility analyses cannot be implemented in early pl...

Lecture notes – Global Classroom – Department of Bioorganic Chemistry – School of Pharmacy – Saarland University Germany – Global Classroom is supported by the DAAD (German Academic Exchange Service)

The large-scale surface-water monitoring infrastructure for Greece Open Hydrosystem Information Network (Openhi.net) is presented in this paper. Openhi.net provides free access to water data, incorporating existing networks that manage their own databases. In its pilot phase, Openhi.net operates three telemetric networks for monitoring the quantity...

Whilst hydrology is a Greek term, it was not in use in the Classical literature, but much later, during the Renaissance, in its Latin form, hydrologia. On the other hand, Greek natural philosophers (or, in modern vocabulary, scientists) created robust knowledge in related scientific areas, to which they gave names such as meteorology, climate and h...

This supplement provides material supporting the analyses and conclusions of the main paper and comprises four sections: S1. On the human teeth problem and the debate of Russell and Aristotle S2. Modern imaginative explanations of the Nile floods S3. The appearance of the term hydrology S4. Original texts of the quotations translated in the artic...

The design of hydropower works typically follows a top-down approach, starting from a macroscopic screening of the broader region of interest, to select promising clusters for hydroelectric exploitation, based on easily retrievable information. Manual approaches are very laborious and may fail to detect sites of significant hydropower potential. In...

In human societies, we observe a wide range of types of stratification, i.e., in terms of financial class, political power, level of education, sanctity, and military force. In financial, political, and social sciences, stratification is one of the most important issues and tools as the Lorenz Curve and the Gini Coefficient have been developed to d...

The fundamental concepts in the field of water-energy systems and their historical evolution with emphasis on recent developments are reviewed. Initially, a brief history of the relation of water and energy is presented and the concept of the water-energy nexus in the 21th century is introduced. The investigation of the relationship between water a...

Whilst hydrology (ὑδρολογία) is a Greek term, it has not been in use in the Classical literature but much later, during the Renaissance, in its Latin version, hydrologia. On the other hand, Greek natural philosophers created robust knowledge in related scientific areas, to which they gave names such as meteorology, climate and hydraulics. These ter...

Due to their negligible storage capacity, small hydroelectric plants cannot offer regulation of flows, thus making the prediction of energy production a very difficult task, even for small time horizons. Further uncertainties arise due to the limited hydrological information, in terms of upstream inflow data, since usually the sole available measur...

As made for most of renewable energy sources, wind energy is driven by highly uncertain and thus unpredictable meteorological processes. In the context of wind power scheduling and control, reliable wind predictions across scales is a challenging problem. However, since the generation of wind energy is, in fact, a nonlinear transformation of wind v...

Over the last 30 years, numerous water resources planning and management studies in Greece have been conducted by using state-of-the-art methodologies and associated computational tools that have been developed by the Itia research team at the National Technical University of Athens. The spearhead of Itia’s research toolkit has been the Hydronomeas...

The Open Hydrosystem Information Network (OpenHi.net) is a state-of-the-art information infrastructure for the collection, management and free dissemination of hydrological and environmental information related to Greece’s surface water resources. It was launched two years ago as part of a the national research infrastructure “Hellenic Integrated M...

We investigate the application of a solar-powered bus route to a small-scale transportation system, as such of a university campus. In particular, we explore the prospect of replacing conventional fossil fuel buses by electric buses powered by solar energy and electricity provided by the central grid. To this end, we employ GIS mapping technology t...

We conduct a large-scale benchmark experiment aiming to advance the use of machine-learning quantile regression algorithms for probabilistic hydrological post-processing “at scale” within operational contexts. The experiment is set up using 34-year-long daily time series of precipitation, temperature, evapotranspiration and streamflow for 511 catch...

We conduct a large-scale benchmark experiment aiming to advance the use of machine-learning quantile regression algorithms for probabilistic hydrological post-processing "at scale" within operational contexts. The experiment is set up using 34-year-long daily time series of precipitation, temperature, evapotranspiration and streamflow for 501 catch...

Quantification of predictive uncertainty in hydrological modelling is often made by post-processing point hydrological predictions using regression models. We perform an extensive comparison of machine learning algorithms in obtaining quantile predictions of daily streamflow under this specific approach. The comparison is performed using a large am...

Quantification of predictive uncertainty in hydrological modelling is often made by post-processing point hydrological predictions using regression models. We perform an extensive comparison of machine learning algorithms in obtaining quantile predictions of daily streamflow under this specific approach. The comparison is performed using a large am...

The protection and management of water and environmental resources require the availability of reliable data, collected by properly designed, equipped and functioning monitoring networks. However, for many years in Greece, the status of data collection and archiving has been far from adequate, thus preventing the country from managing its water res...

For more than two decades, the use of artificial neural networks (ANNs) in hydrology has become an effective and efficient alternative against traditional modeling approaches, i.e. physically-based or conceptual. These can take ad-vantage of any type of available information to predict the hydrological response of complex systems, with missing data...

Integrated modeling of hybrid water-energy systems, comprising conventional and renewable energy sources, pumped-storage facilities and other infrastructures, which aim to serve combined water and energy uses, is a highly challenging problem. On the one hand, such systems are subject to significant uncertainties that span over all associated input...

Ocean energy is considered a promising renewable energy resource mainly due to its massive energy potential. State of the art technologies that can harness the ocean dynamics are discussed in terms of their efficiency and cost of energy production. The ocean related process with the highest potential, but also the highest uncertainty, is the wave p...

Ocean energy is considered a promising renewable energy resource mainly due to its massive energy potential. State of the art technologies that can harness the ocean dynamics are discussed in terms of their efficiency and cost of energy production. The ocean related process with the highest potential, but also the highest uncertainty, is the wave p...

Lecture Notes for the course "Renewable Energy and Hydroelectric Projects" (8th semester, School of Civil Engineering, National Technical University of Athens) on the subject "Simulation and optimization for the design and management of hydroelectric works"

This presentation is in Greek. Some of its content can be found in English in another presentation: "From mythology to science: the development of scientific hydrological concepts in the Greek antiquity", https://www.researchgate.net/publication/324516974

The ever-increasing energy demand has led to overexploitation of fossil fuels deposits, while renewables offer a viable alternative. Since renewable energy resources derive from phenomena related to either atmospheric or geophysical processes, unpredictability is inherent to renewable energy systems. An innovative and simple stochastic tool, the cl...

Since the beginning of the 21st century, the scientific community has made huge leaps to exploit renewable energy sources, with solar radiation being one of the most important. However, the variability of solar radiation has a significant impact on solar energy conversion systems, such as in photovoltaic systems, characterized by a fast and non-lin...

In this study we explore the controls over suspended sediment yield in 11 stations situated along six major rivers of Western – Northern Greece (Arachthos, Achelooos, Evinos, Aoos, Kalamas and Aliakmon). Values of area specific sediment yield for these stations come from reanalysis of existing records, by adaptation of the broken rating curve conce...

In their effort to balance anthropogenic water demand and ecosystem conservation within a sustainable water resources management framework, water managers and stakeholders need sound scientific guidance. In this study, we applied a two-dimensional hydrodynamic habitat model using benthic macroinvertebrates as the target aquatic community, and carri...

While hydrology is a Greek word (υδρoλoγία, from ύδωρ = water and λόγoς = reason), it has not been in use in the classical literature but much later, during the Renaissance, in its Latin version, hydrologia. On the other hand, Greek natural philosophers created robust knowledge in related scientific areas, to which they gave names such as meteorolo...

Since the beginning of the 21st century, the scientific community has made huge leaps to exploit renewable energy sources, with solar radiation being one of the most important. However, the variability of solar radiation has a significant impact on solar energy conversion systems, such as in photovoltaic systems, characterized by a fast and non-lin...

We present a large-scale model-implementing study aiming at the comparison of 3 daily conceptual hydrological models. These models comprise a different number of parameters, i.e. 4, 5 and 6 parameters. The comparison is performed for 340 MOPEX catchments, while each of the modelling approaches is assessed by computing the values of 18 metrics for t...

We present a large-scale model-implementing study aiming at the comparison of 3 daily conceptual hydrological models. These models comprise a different number of parameters, i.e. 4, 5 and 6 parameters. The comparison is performed for 340 MOPEX catchments, while each of the modelling approaches is assessed by computing the values of 18 metrics for t...

The sites where major ancient civilizations were developed had similar climatological and hydrological conditions. All sites have in common warm and dry climate but also abundance of water from a large river crossing the area. However, the sites of ancient Greek civilizations, while they also have warm and dry climate, are located in water deficien...

The heyday of Athens in the fifth century was followed by the Peloponnesian War (431–404 BC), the defeat of the Athenians and the death of the great visionary Pericles. The powerful city of Athens lost its glamor. From 338 BC, the city is under the rule of the Macedonians and, after the conquest of the city by Sulla, Athens finally passes to the Ro...

After its liberation from the Turkish occupation in 1834, Athens started to be reconstructed. The city grew quickly demographically and residentially but the water supplies were not sufficient. There were many functional and cosmetic repairs carried out on the Hadrianic Aqueduct but, for the most part, the water supply of the capital came from spri...

The electrical energy demand (EED) in Greece for the time period 2002–2016 is investigated. The aim of the study is to introduce a framework for the exploratory data analysis (EDA) of the EED in the time domain. To this end, the EED at the hourly, daily, seasonal and annual time scale along with the mean daily temperature and the Gross Domestic Pro...

A detailed investigation of the variability of solar radiation can be proven useful towards more efficient and sustainable design of renewable resources systems. In this context, we analyze observations from Athens, Greece and we investigate the marginal distribution of the solar radiation process at a daily and hourly step, the long-term behavior...

As the electric energy in the non-connected islands is mainly produced by oil-fueled power plants, the unit cost is extremely high due to import cost. The integration of renewable resources in the energy mix is essential for reducing the financial and environmental cost. In this work, various energy resources (renewable and fossil fuels) are evalua...

We present data and code for visualizing the electrical energy data and weather-, climate-related and socioeconomic variables in the time domain in Greece. The electrical energy data include hourly demand, weekly-ahead forecasted values of the demand provided by the Greek Independent Power Transmission Operator and pricing values in Greece. We also...

Non-connected islands to the electric gird are often depending on oil-fueled power plants with high unit cost. A hybrid energy system with renewable resources such as wind and solar plants could reduce this cost and also offer more environmental friendly solutions. However, atmospheric processes are characterized by high uncertainty that does not p...

A detailed investigation of the variability of solar radiation can be proven useful towards more efficient and sustainable design of renewable resources systems. This variability is mainly caused from the regular seasonal and diurnal variation, as well as its stochastic nature of the atmospheric processes, i.e. sunshine duration. In this context, w...

As the electric energy in the non-connected islands is mainly produced by oil-fueled power plants, the unit cost is extremely high. Here the various energy sources are examined in order to create the appropriate electric energy mix for a non-connected Aegean island. All energy sources (renewable and fossil fuels) are examined and each one is evalua...

Interbasin water transfer is a primary instrument of water resources management directly related with the integrated development of the economy, society and environment. Here we assess the project of the interbasin water transfer from the river Acheloos to the river Pinios basin which has intrigued the Greek society, the politicians and scientists...

The Electrical Energy Demand (EED) of the agricultural, commercial and industrial sector in Greece, as well as its use for domestic activities, public and municipal authorities and street lighting are analysed spatially using Geographical Information System and spatial statistical methods. The analysis is performed on data which span from 2008 to 2...

We investigate various uses of electricity demand in Greece (agricultural, commercial, domestic, industrial use as well as use for public and municipal authorities and street lighting) and we examine their relation with variables such as population, total area, population density and the Gross Domestic Product. The analysis is performed on data whi...

Pumped-storage constitutes today a mature method of bulk electricity storage in the form of hydropower. This bulk electricity storability upgrades the economic value of hydropower as it may mitigate –or even neutralize-stochastic effects deriving from various geophysical and socioeconomic factors, which produce numerous load balance inefficiencies...

One-dimensional and quasi-two-dimensional hydraulic freeware models (HEC-RAS, LISFLOOD-FP and FLO-2d) are widely used for flood inundation mapping. These models are tested on a benchmark test with a mixed rectangular-triangular channel cross section. Using a Monte-Carlo approach, we employ extended sensitivity analysis by simultaneously varying the...

Οι υπόγειες δεξαμενές αποτελούν την κυρίαρχη συνιστώσα των έργων ύδρευσης του αρχαίου Πειραιά και είναι αυτές που δίνουν στο υδροσύστημα μια ιδιαίτερη θέση σε σύγκριση με τα υπόλοιπα της αρχαιότητας. Η αναπαράστασή της λειτουργίας τους επιτρέπει τη μελέτη μιας περίπτωσης ευφυούς αξιοποίησης περιορισμένων υδατικών πόρων σε αστική περιοχή. Με την ανά...

Within the ongoing research project “Combined Renewable Systems for Sustainable Energy Development” (CRESSENDO), we have developed a novel stochastic simulation framework for optimal planning and management of large-scale hybrid renewable energy systems, in which hydropower plays the dominant role. The methodology and associated computer tools are...

The Greek electricity system is examined for the period 2002-2014. The demand load data are analysed at various time scales (hourly, daily, seasonal and annual) and they are related to the mean daily temperature and the gross domestic product (GDP) of Greece for the same time period. The prediction of energy demand, a product of the Greek Independe...

Modelling of large-scale hybrid renewable energy systems (HRES) is a challenging task, for which several open computational issues exist. HRES comprise typical components of hydrosystems (reservoirs, boreholes, conveyance networks, hydropower stations, pumps, water demand nodes, etc.), which are dynamically linked with renewables (e.g., wind turbin...

We present a multi-criteria simulation-optimization framework for the optimal design and setting of flood protection structures along river banks. The methodology is tested in the lower course of the Arachthos River (Epirus, Greece), downstream of the hydroelectric dam of Pournari. The entire study area is very sensitive, particularly because the r...

Over its long history, Athens has never had sufficient water resources and the water supply of the city has been an endless and ambitious challenge. Several hydraulic works of various scales and types (from simple wells and cisterns to large aqueducts) have been constructed during this long period. These works helped Athenians to cope with water sc...

Water has played a vital role in life in Greece during its long history. Ancient Greek societies were very active in the field of water management, resulting in an impressive variety of hydraulic works. The main purpose of this paper is to discuss the operation of one of the most ancient and extended hydraulic works, the drainage project of Lake Co...

Potential evapotranspiration (PET) is key input in water resources, agricultural and environmental modelling. For many decades, numerous approaches have been proposed for the consistent estimation of PET at several time scales of interest. The most recognized is the Penman-Monteith formula, which is yet difficult to apply in data-scarce areas, sinc...

Potential evapotranspiration (PET) is key input in water resources, agricultural and environmental modelling. For many decades, numerous approaches have been proposed for the consistent estimation of PET at several time scales of interest. The most recognized is the Penman-Monteith formula, which is yet difficult to apply in data-scarce areas, sinc...

Urban water, wastewater and stormwater management practices in ancient Hellas, from the Minoan to the Roman times are briefly reviewed. In the Prehistoric Hellas palaces and other settlements tended to be located at dry places, at a distance from rivers or lakes. During the Bronze Age decentralized water supply and wastewater and stormwater managem...