Geologist, MSc in Water Resources, PhD candidate
+30 210 772 2837
DEUCALION – Assessment of flood flows in Greece under conditions of hydroclimatic variability: Development of physically-established conceptual-probabilistic framework and computational tools
Duration: March 2011–March 2014
Budget: €145 000
Commissioned by: General Secretariat of Research and Technology
Project director: D. Koutsoyiannis
Principal investigator: N. Mamassis
Programme: ΕΣΠΑ "Συνεργασία"
The project aims to develop a set of physically-based methodologies associated with modelling and forecasting of extreme rainfall events and the subsequent flood events, and adapted to the peculiarities of the hydroclimatic and geomorphological conditions of Greece. It includes the implementation of a set of research river basins that comprises a number of gauged basins in Greece and Cyprus with reliable measurements of adequate length, as well as three new experimental basins (with their sub-basins), which will be equipped with the necessary infrastructure. From the field data analysis (hydrological, meteorological, geographical) physically-established regional models will be devoloped for the estimation of characteristic hydrological design quantities, along with hydrological-hydraulic models, which will be integrated within an operational system for hydrometeorological forecasting. A framework of design criteria and methodologies (in a draft form for discussion) will be prepared for the elaboration of hydrological studies for flood-prevention works.
Project web-page: http://deucalionproject.itia.ntua.gr/
Maintenance, upgrading and extension of the Decision Support System for the management of the Athens water resource system
Duration: October 2008–November 2011
Budget: €72 000
Project director: N. Mamassis
Principal investigator: D. Koutsoyiannis
This research project includes the maintenance, upgrading and extension of the Decision Support System that developed by NTUA for EYDAP in the framework of the research project “Updating of the supervision and management of the water resources’ system for the water supply of the Athens’ metropolitan area”. The project is consisted of the following parts: (a) Upgrading of the Data Base, (b)Upgrading and extension of hydrometeorological network, (c) upgrading of the hydrometeorological data process software, (d) upgrading and extension of the Hydronomeas software, (e) hydrological data analysis and (f) support to the preparation of the annual master plans
P. Dimitriadis, K. Tzouka, D. Koutsoyiannis, H. Tyralis, A. Kalamioti, E. Lerias, and P. Voudouris, Stochastic investigation of long-term persistence in two-dimensional images of rocks, Spatial Statistics, 29, 177–191, doi:10.1016/j.spasta.2018.11.002, 2019.
Determining the geophysical properties of rocks and geological formations is of high importance in many fields such as geotechnical engineering. In this study, we investigate the second-order dependence structure of spatial (two-dimensional) processes through the statistical perspective of variance vs. scale (else known as the climacogram) instead of covariance vs. lag (e.g. autocovariance, variogram etc.) or power vs. frequency (e.g. power spectrum, scaleogram, wavelet transform etc.) which traditionally are applied. In particular, we implement a two-dimensional (visual) estimator, adjusted for bias and for unknown process mean, through the (plot of) variance of the space-averaged process vs. the spatial scale. Additionally, we attempt to link the climacogram to the type of rocks and provide evidence on stochastic similarities in certain of their characteristics, such as mineralogical composition and resolution. To this end, we investigate two-dimensional spatial images of rocks in terms of their stochastic microstructure as estimated by the climacogram. The analysis is based both on microscale and macroscale data extracted from grayscale images of rocks. Interestingly, a power-law drop of variance vs. scale (or else known as long-term persistence) is detected in all scales presenting a similar power-exponent. Furthermore, the strengths and limitations of the climacogram as a stochastic tool are discussed and compared with the traditional tool in spatial statistics, the variogram. We show that the former has considerable strengths for detecting the long-range dependence in spatial statistics.
Share Link: https://authors.elsevier.com/c/1YJjr7su79fMuR
H. Tyralis, P. Dimitriadis, D. Koutsoyiannis, P.E. O’Connell, K. Tzouka, and T. Iliopoulou, On the long-range dependence properties of annual precipitation using a global network of instrumental measurements, Advances in Water Resources, 111, 301–318, doi:10.1016/j.advwatres.2017.11.010, 2018.
The long-range dependence (LRD) is considered an inherent property of geophysical processes, whose presence increases uncertainty. Here we examine the spatial behaviour of LRD in precipitation by regressing the Hurst parameter estimate of mean annual precipitation instrumental data which span from 1916-2015 and cover a big area of the earth’s surface on location characteristics of the instrumental data stations. Furthermore, we apply the Mann-Kendall test under the LRD assumption (MKt-LRD) to reassess the significance of observed trends. To summarize the results, the LRD is spatially clustered, it seems to depend mostly on the location of the stations, while the predictive value of the regression model is good. Thus when investigating for LRD properties we recommend that the local characteristics should be considered. The application of the MKt-LRD suggests that no significant monotonic trend appears in global precipitation, excluding the climate type D (snow) regions in which positive significant trends appear.
Supplementary information files are hosted at: https://doi.org/10.6084/m9.figshare.4892447.v1
H. Tyralis, G. Karakatsanis, K. Tzouka, and N. Mamassis, Data and code for the exploratory data analysis of the electrical energy demand in the time domain in Greece, Data in Brief, 13 (700-702), doi:http://dx.doi.org/10.1016/j.energy.2017.06.074, 2017.
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 present the daily temperature in Athens and the Gross Domestic Product of Greece. The code combines the data to a single report, which includes all visualizations with combinations of all variables in multiple time scales. The data and code we reused in Tyralis et al.(2017)
Full text: http://www.itia.ntua.gr/en/getfile/1825/1/documents/DataAndCode.pdf (127 KB)
M. Chalakatevaki, P. Stamou, S. Karali, V. Daniil, P. Dimitriadis, K. Tzouka, T. Iliopoulou, D. Koutsoyiannis, P. Papanicolaou, and N. Mamassis, Creating the electric energy mix in a non-connected island, Energy Procedia, 125, 425–434, doi:10.1016/j.egypro.2017.08.089, 2017.
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 evaluated using technical, environmental and economic criteria with an emphasis to biomass, pumped hydro storage and replacement of oil power plants. Finally, a synthesis is presented as a toy-model in an Aegean island that satisfies the electric energy demand including base and peak electric loads.
Full text: http://www.itia.ntua.gr/en/getfile/1733/1/documents/electric_mix_energy_procedia.pdf (1118 KB)
Other works that reference this work (this list might be obsolete):
|1.||Bakanos, P. I., and K. L. Katsifarakis, Optimizing operation of a large-scale pumped storage hydropower system coordinated with wind farm by means of genetic algorithm, Global Nest Journal, 2019.|
|2.||Giudici, F., A. Castelletti, E. Garofalo, M. Giuliani, and H. R. Maier, Dynamic, multi-objective optimal design and operation of water-energy systems for small, off-grid islands, Applied Energy, 250, 605-616, doi:10.1016/j.apenergy.2019.05.084, 2019.|
H. Tyralis, G. Karakatsanis, K. Tzouka, and N. Mamassis, Exploratory data analysis of the electrical energy demand in the time domain in Greece, Energy, 134 (902-918), 16 pages, doi:10.1016/j.energy.2017.06.074 0360-5442, 2017.
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 Product (GDP) of Greece are visualized. The forecast of the EED provided by the Greek Independent Power Transmission Operator (IPTO) is also visualized and is compared with the actual EED. Furthermore, the EED pricing system is visualized. The results of the study in general confirm and summarize the conclusions of previous relevant studies in Greece, each one treating a single topic and covering shorter and earlier time periods. Furthermore, some unexpected patterns are observed, which if not considered carefully could result to dubious models. Therefore, it is shown that the EDA of the EED in the time domain coupled with weather-, climate-related and socio-economic variables is essential for the building of a model for the short-, medium- and long-term EED forecasting, something not highlighted in the literature.
Full text: http://www.itia.ntua.gr/en/getfile/1722/1/documents/EDA_electricity_2017.pdf (3406 KB)
P. Dimitriadis, D. Koutsoyiannis, and K. Tzouka, Predictability in dice motion: how does it differ from hydrometeorological processes?, Hydrological Sciences Journal, 61 (9), 1611–1622, doi:10.1080/02626667.2015.1034128, 2016.
From ancients times dice have been used to denote randomness. A dice throw experiment is set up in order to examine the predictability of the die orientation through time using visualization techniques. We apply and compare a deterministic-chaotic and a stochastic model and we show that both suggest predictability in die motion that deteriorates with time just like in hydrometeorological processes. Namely, die’s trajectory can be predictable for short horizons and unpredictable for long ones. Furthermore, we show that the same models can be applied, with satisfactory results, to high temporal resolution time series of rainfall intensity and wind speed magnitude, occurring during mild and strong weather conditions. The difference among the experimental and two natural processes is in the time length of the high-predictability window, which is of the order of 0.1 s, 10 min and 1 h for dice, rainfall and wind process, respectively.
P. Kossieris, Panayiotakis, K. Tzouka, E. Rozos, and C. Makropoulos, An e-Learning approach for improving household water efficiency, Procedia Engineering, WDSA 2014, Bari, Italy, Water Distribution Systems Analysis, 2014.
This paper, presents the development of an e-learning platform, associated with smart metering infrastructure, developed in Moodle. The platform aims to support further householders to improve the water efficiency of their household by understanding their current consumption and identifying practices, technologies that can save water. The platform is built around an interactive, multi-stage, educational process, which begins with a preparatory ("Exposing") stage in which the users receive useful information and feedback about their "water identity", continuous through a self-assessment ("Understanding") stage and finally provides (customized) smart and cost-effective tips and suggestions ("Acting" stage). This paper presents the components of the platform, including, inter alia, FAQ's, quizzes, advanced water calculators and customized tips.
P. Dimitriadis, H. Tyralis, T. Iliopoulou, K. Tzouka, Y. Markonis, N. Mamassis, and D. Koutsoyiannis, A climacogram estimator adjusted for timeseries length; application to key hydrometeorological processes by the Köppen-Geiger classification, European Geosciences Union General Assembly 2018, Geophysical Research Abstracts, Vol. 20, Vienna, EGU2018-17832, European Geosciences Union, 2018.
We present a climacogram estimator (variance of the scaled process vs. scale) that employs all the available information through a pooled time series estimation approach. This method does not discard time-series of short length or of high percentage of missing values; a common practice in hydrometeorology. Furthermore, we estimate and compare the second-order dependence structure (overall and classified by the Köppen-Geiger system) over the last two climatic periods (60 years) for several processes (temperature, dew-point, wind, precipitation, river discharge and atmospheric pressure) using worldwide surface stations. This analysis is performed based on the standardized climacogram, which shows numerous benefits compared to the autocorrelation and standardized power-spectrum.
Full text: http://www.itia.ntua.gr/en/getfile/1800/1/documents/EGU2018-17832.pdf (34 KB)
K. Tzouka, P. Dimitriadis, E. Varouchakis, and D. Koutsoyiannis, Stochastic investigation of the correlation structure of two-dimensional images of rocks from small to large scales, European Geosciences Union General Assembly 2018, Geophysical Research Abstracts, Vol. 20, Vienna, EGU2018-17306-1, European Geosciences Union, 2018.
We investigate the drop of variance vs. scale for geostatistical processes through the use of the climacogram-based variogram (CBV) and climacogram-based power-spectrum (CBS), where climacogram is the (plot of) variance of the space-averaged process vs. the spatial scale. Focus is given to the small and medium scale properties of the rocks and an attempt is made to link the CBV and CBS with these and provide certain stochastic characteristics based on their composition and resolution. The analysis is based both on microscale and macroscale data, as extracted from grayscale images of rocks. Also, comparisons are made, through Monte-Carlo experiments, to the autocovariance-based metrics (such as variogram and power-spectrum) for a variety of common (white noise, Markov and Hurst-Kolmogorov) processes. Finally, a parsimonious model is proposed that can adequately describe the second-order dependence structure of rocks for a large variety of scales.
Full text: http://www.itia.ntua.gr/en/getfile/1793/1/documents/EGU2018-17306-1.pdf (31 KB)
P. Dimitriadis, K. Tzouka, H. Tyralis, and D. Koutsoyiannis, Stochastic investigation of rock anisotropy based on the climacogram, European Geosciences Union General Assembly 2017, Geophysical Research Abstracts, Vol. 19, Vienna, EGU2017-10632-1, European Geosciences Union, 2017.
Anisotropy plays an important role on rock properties and entails valuable information for many fields of applied geology and engineering. Many methods are developed in order to detect transitions from isotropy to anisotropy but as a scale–depended effect, anisotropy also needs to be determined in multiple scales. We investigate the application of a stochastic tool, the climacogram (i.e. variance of the averaged process vs. scale) to characterize anisotropy in rocks at different length scales through image processing. The data are pictures from laboratory, specifically thin sections, and pictures of rock samples and rock formations in the field in order to examine anisotropy in nano, micro and macroscale.
H. Tyralis, P. Dimitriadis, T. Iliopoulou, K. Tzouka, and D. Koutsoyiannis, Dependence of long-term persistence properties of precipitation on spatial and regional characteristics, European Geosciences Union General Assembly 2017, Geophysical Research Abstracts, Vol. 19, Vienna, EGU2017-3711, doi:10.13140/RG.2.2.13252.83840/1, European Geosciences Union, 2017.
The long-term persistence (LTP), else known in hydrological science as the Hurst phenomenon, is a behaviour observed in geophysical processes in which wet years or dry years are clustered to respective long time periods. A common practice for evaluating the presence of the LTP is to model the geophysical time series with the Hurst-Kolmogorov process (HKp) and estimate its Hurst parameter H where high values of H indicate strong LTP. We estimate H of the mean annual precipitation using instrumental data from approximately 1 500 stations which cover a big area of the earth’s surface and span from 1916 to 2015. We regress the H estimates of all stations on their spatial and regional characteristics (i.e. their location, elevation and Köppen-Geiger climate class) using a random forest algorithm. Furthermore, we apply the Mann-Kendall test under the LTP assumption (MKt-LTP) to all time series to assess the significance of observed trends of the mean annual precipitation. To summarize the results, the LTP seems to depend mostly on the location of the stations, while the predictive value of the fitted regression model is good. Thus when investigating for LTP properties we recommend that the local characteristics should be considered. Additionally, the application of the MKt-LTP suggests that no significant monotonic trend can characterize the global precipitation. Dominant positive significant trends are observed mostly in main climate type D (snow), while in the other climate types the percentage of stations with positive significant trends was approximately equal to that of negative significant trends. Furthermore, 50% of all stations do not exhibit significant trends at all.
Full text: http://www.itia.ntua.gr/en/getfile/1695/1/documents/EGU2017-3711presentation_.pdf (1608 KB)
V. Daniil, G. Pouliasis, E. Zacharopoulou, E. Demetriou, G. Manou, M. Chalakatevaki, I. Parara, C. Georganta, P. Stamou, S. Karali, E. Hadjimitsis, G. Koudouris, E. Moschos, D. Roussis, K. Papoulakos, A. Koskinas, G. Pollakis, N. Gournari, K. Sakellari, Y. Moustakis, N. Mamassis, A. Efstratiadis, H. Tyralis, P. Dimitriadis, T. Iliopoulou, G. Karakatsanis, K. Tzouka, I. Deligiannis, V. Tsoukala, P. Papanicolaou, and D. Koutsoyiannis, The uncertainty of atmospheric processes in planning a hybrid renewable energy system for a non-connected island, European Geosciences Union General Assembly 2017, Geophysical Research Abstracts, Vol. 19, Vienna, EGU2017-16781-4, doi:10.13140/RG.2.2.29610.62406, European Geosciences Union, 2017.
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 permit harvesting and utilizing full of their potential. Therefore, a more sophisticated framework that somehow incorporates this uncertainty could improve the performance of the system. In this context, we describe several stochastic and financial aspects of this framework. Particularly, we investigate the cross-correlation between several atmospheric processes and the energy demand, the possibility of mixing renewable resources with the conventional ones and in what degree of reliability, and critical financial subsystems such as weather derivatives. A pilot application of the above framework is also presented for a remote island in the Aegean Sea.
Full text: http://www.itia.ntua.gr/en/getfile/1689/1/documents/EGU2017oral_16781_final.pdf (3038 KB)
Other works that reference this work (this list might be obsolete):
|1.||#Vashisth, P. K. Agrawal, N. Gupta, K. R. Naizi, and A. Swarnkar, A novel strategy for electric vehicle home charging to defer investment on distributed energy resources, 2023 IEEE IAS Global Conference on Renewable Energy and Hydrogen Technologies (GlobConHT), Male, Maldives, doi:10.1109/GlobConHT56829.2023.10087723, 2023.|
P. Stamou, S. Karali, M. Chalakatevaki, V. Daniil, K. Tzouka, P. Dimitriadis, T. Iliopoulou, P. Papanicolaou, D. Koutsoyiannis, and N. Mamassis, Creating the electric energy mix of a non-connected Aegean island, European Geosciences Union General Assembly 2017, Geophysical Research Abstracts, Vol. 19, Vienna, EGU2017-10130-10, doi:10.13140/RG.2.2.36537.77927, European Geosciences Union, 2017.
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 evaluated using technical, environmental and economic criteria. Finally the most appropriate energy sources are simulated considering the corresponding energy works. Special emphasis is given to the use of biomass and the possibility of replacing (even partially) the existing oil-fueled power plant. Finally, a synthesis of various energy sources is presented that satisfies the electric energy demand taking into account the base and peak electric loads of the island.
Full text: http://www.itia.ntua.gr/en/getfile/1688/2/documents/posterEGU.pdf (2687 KB)
G. Karakatsanis, H. Tyralis, and K. Tzouka, Entropy, pricing and productivity of pumped-storage, European Geosciences Union General Assembly 2016, Geophysical Research Abstracts, Vol. 18, Vienna, European Geosciences Union, 2016.
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 due to increased uncertainty. Pumped-storage further holds a key role for unifying intermittent renewable (i.e. wind, solar) units with controllable non-renewable (i.e. nuclear, coal) fuel electricity generation plants into integrated energy systems. We develop a set of indicators for the measurement of performance of pumped-storage, in terms of the latter's energy and financial contribution to the energy system. More specifically, we use the concept of entropy in order to examine: (1) the statistical features -and correlations- of the energy system's intermittent components and (2) the statistical features of electricity demand prediction deviations. In this way, the macroeconomics of pumped-storage emerges naturally from its statistical features (Karakatsanis et al. 2014). In addition, these findings are combined to actual daily loads. Hence, not only the amount of energy harvested from the pumped-storage component is expected to be important, but the harvesting time as well, as the intraday price of electricity varies significantly. Additionally, the structure of the pumped-storage market proves to be a significant factor as well for the system's energy and financial performance (Paine et al. 2014). According to the above, we aim at postulating a set of general rules on the productivity of pumped-storage for (integrated) energy systems.
Full text: http://www.itia.ntua.gr/en/getfile/1854/1/documents/EGU_2016_GK_15481.pdf (3409 KB)
Y. Markonis, T. Dimoulas, A. Atalioti, C. Konstantinou, A. Kontini, Μ.-Ι. Pipini, E. Skarlatou, V. Sarantopoulos, K. Tzouka, S.M. Papalexiou, and D. Koutsoyiannis, Comparison between satellite and instrumental solar irradiance data at the city of Athens, Greece, European Geosciences Union General Assembly 2015, Geophysical Research Abstracts, Vol. 17, Vienna, EGU2015-5719, doi:10.13140/RG.2.2.12274.09920, European Geosciences Union, 2015.
In this study, we examine and compare the statistical properties of satellite and instrumental solar irradiance data at the capital of Greece, Athens. Our aim is to determine whether satellite data are sufficient for the requirements of solar energy modelling applications. To this end we estimate the corresponding probability density functions, the auto-correlation functions and the parameters of some fitted simple stochastic models. We also investigate the effect of sample size to the variance in the temporal interpolation of daily time series. Finally, as an alternative, we examine if temperature can be used as a better predictor for the daily irradiance non-seasonal component instead of the satellite data.
H. Tyralis, G. Karakatsanis, K. Tzouka, and N. Mamassis, Analysis of the electricity demand of Greece for optimal planning of a large-scale hybrid renewable energy system, European Geosciences Union General Assembly 2015, Geophysical Research Abstracts, Vol. 17, Vienna, EGU2015-5643, European Geosciences Union, 2015.
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 Independent Power Transmission Operator, is also compared with the demand load. Interesting results about the change of the electricity demand scheme after the year 2010 are derived. This change is related to the decrease of the GDP, during the period 2010-2014. The results of the analysis will be used in the development of an energy forecasting system which will be a part of a framework for optimal planning of a large-scale hybrid renewable energy system in which hydropower plays the dominant role.
A. Koukouvinos, D. Nikolopoulos, A. Efstratiadis, A. Tegos, E. Rozos, S.M. Papalexiou, P. Dimitriadis, Y. Markonis, P. Kossieris, H. Tyralis, G. Karakatsanis, K. Tzouka, A. Christofides, G. Karavokiros, A. Siskos, N. Mamassis, and D. Koutsoyiannis, Integrated water and renewable energy management: the Acheloos-Peneios region case study, European Geosciences Union General Assembly 2015, Geophysical Research Abstracts, Vol. 17, Vienna, EGU2015-4912, doi:10.13140/RG.2.2.17726.69440, European Geosciences Union, 2015.
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 tested in two major adjacent river basins in Greece (Acheloos, Peneios) extending over 15 500 km2 (12% of Greek territory). River Acheloos is characterized by very high runoff and holds ~40% of the installed hydropower capacity of Greece. On the other hand, the Thessaly plain drained by Peneios – a key agricultural region for the national economy – usually suffers from water scarcity and systematic environmental degradation. The two basins are interconnected through diversion projects, existing and planned, thus formulating a unique large-scale hydrosystem whose future has been the subject of a great controversy. The study area is viewed as a hypothetically closed, energy-autonomous, system, in order to evaluate the perspectives for sustainable development of its water and energy resources. In this context we seek an efficient configuration of the necessary hydraulic and renewable energy projects through integrated modelling of the water and energy balance. We investigate several scenarios of energy demand for domestic, industrial and agricultural use, assuming that part of the demand is fulfilled via wind and solar energy, while the excess or deficit of energy is regulated through large hydroelectric works that are equipped with pumping storage facilities. The overall goal is to examine under which conditions a fully renewable energy system can be technically and economically viable for such large spatial scale.
Other works that reference this work (this list might be obsolete):
|1.||Stamou, A. T., and P. Rutschmann, Pareto optimization of water resources using the nexus approach, Water Resources Management, 32, 5053-5065, doi:10.1007/s11269-018-2127-x, 2018.|
|2.||Stamou, A.-T., and P. Rutschmann, Optimization of water use based on the water-energy-food nexus concept: Application to the long-term development scenario of the Upper Blue Nile River, Water Utility Journal, 25, 1-13, 2020.|
P. Dimitriadis, K. Tzouka, and D. Koutsoyiannis, Windows of predictability in dice motion, Facets of Uncertainty: 5th EGU Leonardo Conference – Hydrofractals 2013 – STAHY 2013, Kos Island, Greece, doi:10.13140/RG.2.2.19417.52322, European Geosciences Union, International Association of Hydrological Sciences, International Union of Geodesy and Geophysics, 2013.
Dice throw experiments are performed based on visualization techniques. Video frames taken with frequency of 120 Hz are retrieved making it possible to monitor the dice trajectories in time and space. A statistical analysis is performed on the observations and a model is built to predict the state of the die a few frames later. The time window for which the prediction has some skill is then studied. The results show that even in dice throws, which are commonly used to symbolize randomness, there is some predictability for short horizons.
Full text: http://www.itia.ntua.gr/en/getfile/1394/1/documents/2013Kos_DiceGame_1.pdf (1945 KB)
P. Dimitriadis, D. Koutsoyiannis, C. Onof, and K. Tzouka, Multidimensional Hurst-Kolmogorov process for modelling temperature and rainfall ﬁelds, European Geosciences Union General Assembly 2011, Geophysical Research Abstracts, Vol. 13, Vienna, EGU2011-739, doi:10.13140/RG.2.2.12070.93761, European Geosciences Union, 2011.
A multidimensional (MD) stochastic simulation model is presented, which is a direct extension of the 1D simple scaling process, known as Hurst-Kolmogorov (HK) process following the analysis of the 2D extension of Koutsoyiannis et al. (2011). The MD HK process can generate time-varying spatial geophysical ﬁelds (such as rainfall and temperature), consistent with the observed long-term spatiotemporal persistence (slowly decaying autocorrelation over spatial or temporal displacement). The MD HK process is formulated assuming anisotropy, so as to take into account possibly different autocorrelation decay rates (Hurst coefﬁcients) in each dimension of the ﬁeld. The MD HK process is also investigated through some applications based on observed temperature and rainfall ﬁelds.
K. Tzouka, Interpretation of conceptual hydrologic model parameters with watershed characteristics. Exploration using the model Zygos, Postgraduate Thesis, 247 pages, NTUA, Athens, June 2007.
Watershed runoff depends on many factors such as: geology (rock permeability), morphology (slopes, geometry of river net, human interferences) and rainfall (intensity, duration and distribution on catchment area). The current thesis investigates the hydrological and hydrogeological parameters of lumped conceptual water balanced model ZYGOS which has been planned and constructed by research team of ITIA of National Technical University of Athens. Although ZYGOS model, like most models of this category, constitute an incorporated algorithm for the optimization of its parameters, the results are not always representative or even close to their true values. The parameters of the model have been calibrated after many experiments and there has been an effort to be interpreted and explained firstly according to the hydrogeological characteristics of 10 Greek river basins and particularly according to the types of rocks, their proportion of participation in the basin and according to the percentage of the basic water streams that flow on the geological formations. Secondly, information has been taken into account about altitude, morphologic slopes of basins, the appearance of springs, sea water intrusion in fresh aquifers, land usages, the tectonic status of the studied area and the construction and operation of technical works (reservoirs, net irrigation etc). Most of the above mentioned information has been taken into account in an indirect way for the interpretation of the results of the model. At the end of each basin analysis it is given a description of Nash coefficient sensitivity in variations of the parameters of the model and a justification for its fluctuations and its optimum values that have been defined. Finally in the chapter of conclusions the optimum values of Nash coefficient and the parameters of the model are presented in total in a table for all 10 basins.
Full text: http://www.itia.ntua.gr/en/getfile/873/1/documents/2007_tzouk.pdf (12134 KB)
Other works that reference this work (this list might be obsolete):
|1.||Charizopoulos, N., and A. Psilovikos, Hydrologic processes simulation using the conceptual model Zygos: the example of Xynias drained Lake catchment (central Greece), Environmental Earth Sciences, doi:10.1007/s12665-016-5565-x, 2016.|
|2.||Charizopoulos, N., A. Psilovikos, and E. Zagana, A lumped conceptual approach for modeling hydrological processes: the case of Scopia catchment area, Central Greece, Environmental Earth Sciences, 76:18, doi:10.1007/s12665-017-6967-0, 2017.|
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A. Efstratiadis, A. Koukouvinos, E. Michailidi, E. Galiouna, K. Tzouka, A. D. Koussis, N. Mamassis, and D. Koutsoyiannis, Description of regional approaches for the estimation of characteristic hydrological quantities, DEUCALION – Assessment of flood flows in Greece under conditions of hydroclimatic variability: Development of physically-established conceptual-probabilistic framework and computational tools, Contractors: ETME: Peppas & Collaborators, Grafeio Mahera, Department of Water Resources and Environmental Engineering – National Technical University of Athens, National Observatory of Athens, 146 pages, September 2014.
The objective of the report is the systematic investigation and evaluation of regional relationships and associated event-based models that are applied in flood studies, through validating their predictions across the pilot basins of the project. The research focuses on the most popular, in Greece as well as globally, hydrological design procedure, which is based on the application of the SCS-CN method for the estimation of hydrological losses, combined with the unit hydrograph theory for the transformation of surface runoff to flood hydrograph at the basin outlet. In the report are investigated both the theoretical-conceptual background of the models as well as the procedure for estimating their basic input quantities (time of concentration, runoff curve number, initial abstraction ratio, initial soil moisture conditions). In this respect, we analyzed more than 100 flood events in 11 sites of interest, which we attempted to represent through several alternative approaches. The analyses showed that it is essential to revise critical aspects of the hydrological design. The most important are: (a) the correction of the time of concentration, as estimated by the Giandotti formula, according to the rainfall intensity; (b) the estimation of parameter CN of the SCS-CN method on the basis of three characteristic layers of spatial information and its adjustment for given initial abstraction ratio; (c) the application of a parametric synthetic unit hydrograph, the time parameters of which depend not only on the characteristics of the basin’s surface but also the mechanisms of the shallow soil; and (d) the statistically consistent estimation of the flood design quantities on the basis of the probabilities of occurrence of the design rainfall under dry, medium or wet antecedent soil moisture conditions.
Related project: DEUCALION – Assessment of flood flows in Greece under conditions of hydroclimatic variability: Development of physically-established conceptual-probabilistic framework and computational tools
Full text: http://www.itia.ntua.gr/en/getfile/1495/1/documents/Report_3_3.pdf (28157 KB)