O. Tzoraki

University of the Aegean · Department of Marine Sciences

Nature is directly affected by drought, threatening human societies, ecosystems, and especially aquatic environments. This research is about: (i) monitoring the meteorological drought on the Guenniche Basin (Northern Tunisia) using the standardized precipitation index (SPI) and the standardized precipitation–evapotranspiration index (SPIE) based on...

Greece has a coastline of about 16,000 km where most of its population, infrastructure, assets and socio-economic activity are concentrated. Most large urban and industrial conglomerates are located at the coast, as well as critical infrastructure such as its many seaports. Coastal areas also form the pillar of Greek tourism, a vital economic secto...

Temporary streams are a key component of the hydrological cycle in arid and semi-arid regions, but their flow is highly variable and difficult to measure. In this paper, we present a novel approach that could be used to assess the flow of temporary streams this allowing to characterize their environmental status. Specifically, we apply the Image Ve...

The occurrence of flash floods in urban catchments within the Mediterranean climate zone has witnessed a substantial rise due to climate change, underscoring the urgent need for early-warning systems. This paper examines the implementation of an early flood monitoring and forecasting system (EMFS) to predict the critical overflow level of a small u...

The current study presents a comprehensive review of worldwide waterborne parasitic protozoan outbreaks reported between 2017 and 2022. Totally, 416 outbreaks were attributed to waterborne transmission of parasitic protozoa. Cryptosporidium was the etiological agent in 77.4% (322) of the outbreaks, while Giardia was reported in 17.1% (71). Toxoplas...

This short contribution provides a brief overview of the drivers and impacts of beach erosion at the Greek islands and Cyprus, which are under an increasing risk of erosion. The most significant beach erosion drivers have been found to be the mean and extreme sea level rise, as well as various geological (e.g., the geological setting and the dimini...

The coastal zone is a vital natural resource extensively used by the population for various activities. Given the human pressures and climate change, it is crucial to comprehend the modifications occurring in the coastal environment and its exposure to erosion. The InVEST Coastal Vulnerability Model is employed to qualitatively assess vulnerability...

As a network of researchers we release an open-access database (EUSEDcollab) of water discharge and suspended sediment yield time series records collected in small to medium sized catchments in Europe. EUSEDcollab is compiled to overcome the scarcity of open-access data at relevant spatial scales for studies on runoff, soil loss by water erosion an...

Groundwater vulnerability assessment has nowadays evolved into an essential tool towards proper groundwater protection and management, while the DRASTIC method is included among the most widely applied vulnerability assessment methods. However, the high uncertainty of the DRASTIC method mainly associated with the subjectivity in assigning parameter...

Temporary streams are a key component of the hydrological cycle in arid and semi-arid regions, but their flow is highly variable and difficult to measure. In this paper, we present a novel approach that could be used to assess the flow of temporary streams and characterize their environmental status. Specifically, we apply the Image Velocimetry met...

The structure and growth of the autochthonous population of Squalius platyceps in the Brestica Stream and the allochthonous population of the same species in the Upper Zeta River were studied based on the examination of 232 specimens. The mean length was 15.7 ± 5 cm in the Brestica Stream and 18.1 ± 3.8 cm in the Upper Zeta River. The mean weight w...

This study presents the development of a vulnerability assessment methodology combining both hydraulic and oceanographic values to evaluate the fragility of the island's coast, subject to floods. The study area covers the coastal part Petra-Molyvos in West-North Lesvos Island, Greece. Petra stream drains the catchment area of 7.97 km 2. The flooded...

Precipitation changes caused by climate change are a phenomenon that may have far more serious consequences in urban areas than previously thought. Preventing the flood extent in rural and urban areas is crucial for the protection of human well-being and private and public land, and for the prevention of human casualties. Modeling potential floods...

Acid mine drainage (AMD) threats the soils and water bodies in the territories of the sulfide mining activities all over the world. Bouaazza’s mine (NE Morocco) lead and sulfides exploitation resulted in the surface exposure of large superficies of acid discharges. The results of physicochemical and geochemical analysis indicate an acidic pH (3.0 –...

In vulnerable areas, where floods are frequent, decision-making through participatory workshops has proved highly applicable and yielded positive results in integrated management issues. This paper examines Nature-Based Solutions (NBS) to provide flood risk mitigation and proactive adaptation options. The case study concerns the Kalloni river basin...

The study of plumes occurring at the mouth of small rivers of temporal flow is a challenging task due to the lack of sedimentological and flow data of appropriate spatiotemporal scales. The present contribution examined the case of a typical un-gauged intermittent Mediterranean stream located in Northern Crete (Xiropotamos river). The SWAT (soil an...

Twenty (20) shallow wells were sampled during the dry season (October 2015) from the Guenniche plain (Northern Tunisia) and examined for their suitability for irrigation. The physicochemical analysis results are used to estimate 10 indexes: the sodium absorption ratio (SAR), percentage of sodium (Na %), residual sodium carbonate (RSC), permeability...

High concentrations of heavy metals (HMs) in water (e.g., As, Cr, and Cd) are harmful to human health, especially to children. HMs’ (As, Cd, Mn, Fe, Cu, Hg, Zn, Cr, and Se) values have been determined from the water of the Guenniche plain (Tunisia); then the carcinogenic risk (CR) and non-carcinogenic Risk (N-CR) were estimated through ingestion an...

Surface water quality is among the significant challenges in the Sutlej River basin, passing through Pakistan's most densely populated province. Currently, the overall surface water quality is grossly polluted, mainly due to the direct discharge of wastewater from the urban areas to the Sutlej River directly or through stream networks. Escherichia...

In these times of strong pressure on aquatic ecosystems and water resources due to climate change and water abstraction, intermittent rivers and ephemeral streams (IRES) (rivers that periodically cease to flow and/or dry) have become valuable assets. Indeed, not only do they supply water but they also offer services for humanity. Despite a growing...

The last decade increasing attention to litter accumulation in the marine environment revealed the issue of the terrestrial fluxes of plastic pollution into the oceans. However, limited studies investigate the macro-litter abundance and composition particularly in freshwater ecosystems and the adjusted coastal environment. In this study, we conduct...

The Guenniche deep aquifer (from 75 to 300 m), located in the Bizerte governorate (North Tunisia), is used to supply water for drinking, irrigation, and other needs. It is underlying three small-scale industrial zones and an agricultural area that uses chemical fertilizers and animal manure to improve soil fertility. The present research deals with...

This e-Poster was created for : HydroMediT 2021 4th International Congress on Applied Ichthyology, Oceanography & Aquatic Environment

This e-Poster was created for : HydroMediT 2021 4th International Congress on Applied Ichthyology, Oceanography & Aquatic Environment

Seawater intrusion poses a serious threat to coastal regions, since it limits the supply of potable drinking water, while it causes the efficiency of crop production to reduce. In an effort to control seawater intrusion and mitigate its negative effects, various protective measures can be implemented. Within this framework, the present study invest...

Today coastal erosion is usually exacerbated by anthropogenic climate change and results in the loss of income and cultural norms, as well as in the loss or degradation of ecosystem services. Public perceptions and participation have an important role – often a legal one – in coastal management and response to coastal hazards. The objective of this...

Environmental flows are unanimously considered to be one of the most comprehensive indicators of the rivers health and their capacities to provide ecosystem goods and services. In this study, the objective was to predict the response of environmental flow components in a typical North African rivers network to future climate change. The study water...

The ongoing ‘refugee crisis’ of the past years has led to the migration of refugee researchers (RRs) to European countries. Due to the COVID-19 pandemic, RRs often had to work from home and/or to continue their social, cultural and economic integration process under new conditions. An online survey carried out to explore the impact of the pandemic...

This study explores the educational level of migrants arriving in Europe since 2015 and makes suggestions to improve their integration into the labor market. The research methodology is based on qualitative (ethnographic research) and quantitative analysis using questionnaires distributed in four languages to the refugee scientists living in Moria...

The erosion of sandy beaches creates a significant impact on the local society, the economy and the environment. The present study is an attempt to adapt the innovative DESSIN (Demonstrate Ecosystem Services Enabling Innovation in the Water Sector) framework that specializes in freshwater applications, to urban coastal systems. The framework is app...

Surface-groundwater interactions in intermittent rivers and ephemeral streams (IRES), waterways which do not flow year-round, are spatially and temporally dynamic because of alternations between flowing, non-flowing and dry hydrological states. Interactions between surface and groundwater often create mixing zones with distinct redox gradients, pot...

Flow data visualizations describe runoff, flooding or drought, showing the interconnectivity and complexity of water data issues or water management problems. Intermittent Flow Rivers constitute more than half of the length of the global river network and their presence is expanding in response to climate change. A new approach is developed to visu...

Frequency of flash floods and droughts in the Mediterranean climate zone is expected to rise in the coming years due to change of its climate. The assessment of the climate change impact at a basin scale is essential for developing mitigation and adaptation plans. This study analyses the variation of the hydrologic regime of a small Mediterranean r...

The accuracy of photogrammetry for geohazards monitoring has improved within the last years because of the "drone revolution". This study is an attempt to perform morphometric measurements in a landslide event that took place near the village Nea Zichni in Northern Greece. The DJI Mavic 2 Pro was selected to capture orthoimages of the entire area i...

Sustainable water resources management plans require advanced instrumentation to measure accurately both the water velocity and the discharge of the aquatic bodies. An innovative way to achieve this goal is with the use of non-contact, cost-effective, and efficient image-based methods. A studied water surface can be captured by subsequent images wh...

Contamination of groundwater by trace elements causes unacceptable human health problems both in short- and long-term. In order to examine the concentration of nine trace elements (Mn, Fe, Cu, Zn, Hg, As, Cr, Cd, and Se), shallow groundwater samples were collected from twenty wells along Guenniche plain, which is one of the most important regions o...

Intermittent rivers and ephemeral streams (IRES) are increasingly studied because of their often-unique aquatic and terrestrial biodiversity, biogeochemical processes and associated ecosystem services. This study is the first to examine the hydrological, physicochemical and taxonomic variability during the dry-wet transition of an intermittent rive...

Climate change projections predict the increase of no-rain periods and storm intensity resulting in high hydrologic alteration of the Mediterranean rivers. Intermittent flow Rivers and Ephemeral Streams (IRES) are particularly vulnerable to spatiotemporal variation of climate variables, land use changes and other anthropogenic factors. In this work...

The disinfecting properties of sun (heat and UV radiation) are adequate in warm sunny regions to rid beach sand of coronavirus particles, if present. Here we detail the mechanism of natural disinfection offered by the sun on coronaviral particles that may find their way onto beach sand. We conclude that heat and UV radiation generated by the sun de...

Capturing and recording fluvio-geomorphological events is essential since these events can be very sudden and hazardous. Climate change is expected to increase flash floods intensity and frequency in the Mediterranean region, thus enhancing such events will also impact the adjacent riparian vegetation. The aim of this study was to capture and recor...

Intermittent rivers are prevalent in many countries across Europe, but little is known about the temporal evolution of intermittence and its relationship with climate variability. Trend analysis of the annual and seasonal number of zero-flow days, the maximum duration of dry spells and the mean date of the zero-flow events is performed on a databas...

Nowadays there is a higher need of strict and broader legislation in waste electrical and electronic equipment (WEEE) recycling industry to reduce environmental effects of WEEE. Environmental challenges include pollution, exhaustion of natural resources, waste management and reduction of landfills. High speed in technological development in many se...

The study of the influence of climate change on the evolution of floods in areas under the influence of a Mediterranean climate is very important. This work aims to provide new analytical elements to decision-makers in flood management and forecasting in three Mediterranean catchments (Lonquen, Evrotas, and Azzaba), in order to better understand th...

Monitoring the groundwater quality situation and identifying the various pollution loads’ sources are a prerequisites to finding solutions. In many areas, nitrate and salinity are one of the prime pollutants in the groundwater. This investigation is carried to present the results of a monitoring study focusing on 20 wells samples collected from the...

In arid and semi-arid parts of the world, river exploitation is intensive, involving water storage for irrigation or hydropower generation. In Greece, 100 small hydropower plants (SHPs) take advantage of less than 10% of the hydropower potential of low flow streams (<2 m3/s), a very small amount in relation to the 70% of the European Union. The ene...

SMIRES is a COST Action addressing the Science and Management of Intermittent Rivers & Ephemeral Streams (coord. T. Datry, INRAE, and G. Singer, University of Innsbruck; http://www.smires.eu). This COST Action had brought together scientists from various research field and stakeholders to develop a European multidisciplinary network for synthesisin...

SMIRES is a COST Action addressing the Science and Management of Intermittent Rivers & Ephemeral Streams (coord. T. Datry, INRAE, and G. Singer, University of Innsbruck; http://www.smires.eu). This COST Action had brought together scientists from various research field and stakeholders to develop a European multidisciplinary network for synthesisin...

The objective of the current work is to develop a methodology of visualization through time-lapse video to show flow changes over time.

Fluviogeomorphologic processes such as bank erosion and deposition affect and change the shape and condition of river and stream channels. Erosion and deposition rates are dependent on many natural (e.g. climate, geology, vegetation, topography) and anthropogenic (e.g. dams, bridges, gabions, straightening, wildfires etc.) factors. Alterations to t...

Abstract: The Guenniche plain located in the northeast of Tunisia is characterized by semi- arid climate and, mean rainfall of 600 mm/year. It is a collapsed basin covered by quaternary sediments in its major area. It contains phreatic and deep aquifers, which are important for the economic activities of the region. The aquifers are intensively exp...

Pharmaceuticals and related compounds are increasingly being released into the marine environment, posing health risks to living organisms. Their accurate determination in marine samples is still an analytical challenge, while they can undergo a series of transformation processes resulting in largely unknown transformation products and health effec...

An e‐waste recycling plant's ecological burden is correlated to soil and water, inside and outside the plant with inductively coupled plasma‐mass spectrometry. Correlation between heavy metal concentrations was calculated with Spearman's rho correlation coefficients. Ecological risk was assessed with ecological risk indexes (RIs) such as Hakanson's...

Managed Aquifer Recharge (MAR) is becoming an attractive water management option, with more than 230 sites operating in Europe. The quality of the produced water for irrigation processes is strongly depended on the aquifers hydrogeochemical characteristics and on the MAR design and operation. The objective of the current work is to study the effici...

Abstract: The Guenniche plain located in the northeast of Tunisia is characterized by semi- arid climate and, mean rainfall of 600 mm/year. It is a collapsed basin covered by quaternary sediments in its major area. It contains phreatic and deep aquifers, which are important for the economic activities of the region. The aquifers are intensively exp...

Since 2015, a large number of migrants (refugees and asylum seekers) from the Middle East, Asia, and Africa have arrived in Greece and continued their onward journey to western European countries where they settled. As various European Union (EU) countries have later blocked the flow of migrants from Greece to their final destination, thousands of...

Stream velocity and flow are very important parameters that must be measured accurately to develop effective water resource management plans. There are various methods and tools to measure the velocity but, nowadays, image-based methods are a promising alternative that does not require physical contact with the water body. The current study describ...

This paper examines the trace elements level in the shallow groundwater of the Guenniche plain (North Tunisia) and its suitability for drinking water use in comparison with national (NT 2013) and international (WHO 2006) standards. Samples collected from twenty (20) wells and ten (10) streams in May 2016 were analyzed for the most common trace elem...

In this study, 17 hydrologists with different experience in hydrological modelling applied the same conceptual catchment model (HBV) to a Greek catchment, using identical data and model code. Calibration was performed manually. Subsequently, the modellers were asked for their experience, their calibration strategy, and whether they enjoyed the exer...

The present study presents a transdisciplinary effort in searching, selecting, developing and implementing indicators for the assessment of ecosystem services (ESs) in the coastal zone. Despite the various classifications developed in recent years, the majority of the relevant studies result in qualitative evaluations of the main ESs of the coastal...

Poster submission for the HydroMediT 2018 International Congress on Applied Ichthyology, Congress on Applied Ichthyology, Oceanography & Aquatic Enviroment.

This contribution addresses the need for a simple model for managers to employ when planning strategies for the management of touristic beaches under sea level rise. A methodological framework was developed and tested in two Aegean archipelago islands (Lesvos and Rhodes, Greece). The scheme can represent the status of touristic island beaches, base...

Waste Electrical and Electronic Equipment (WEEE) produced globally are estimated 20-50 millions tons annualy and only 15-20% of that part is recycled. Even though recycling of e-waste can supply with huge amounts of raw materials, at the same time informal recycling is a lasting environmental problem. E-waste contain persistent organic pollutants,...

The importance of sustainable development of river systems based on ecological and socio-economic criteria is widely recognized. The 'Integrated Valuation of Ecosystem Services and Tradeoffs' (InVEST) model, an ecosystem based model which couples biophysical and economic models, is used to examine the nutrient and bacteria mitigation processes in t...

The quantification of soil moisture under different soils and crops at regional scale is a challenging task. Hence, such studies are limited by the availability of ground based measurements. The current study evaluates the spatial and temporal patterns of daily soil moisture simulated by the Soil and Water Assessment Tool (SWAT) for the upper 30 cm...

Beaches, which form the most significant natural resource of the Aegean Archipelago, are under increasing erosion risk due to projected mean sea level rise (MSLR) and changes in the magnitude/frequency of extreme sea levels (ESLS). In the framework of the ERABEACH project, the erosion risk of all beaches of 6 Aegean islands (Lesvos, Chios, Thira, K...

The objective of this study was to evaluate the risks associated with nutrient and heavy metal pollution in the water and sediments of Kouris Reservoir in Cyprus, and to recommend applicable measures to alleviate them. The reservoir drainage area contains various historic abandoned copper mines existing in an ophiolite geological substrate. Kouris...

A new framework is developed to guide the assessment of the sediments deposition from the upland/upstream areas to island beaches. The study of the coastal sediment supply of insular river basins involves the collection and analysis of meteorological and geomorphological data, the assessment of climatic trends and the use of erosion models to estim...

This research paper focuses on the implementation of the "abcd" water mass balance model in Evrotas River Basin for the runoff simulation. The study area, which is located in Greece and more specifically at SE. Peloponnese, is the Evrotas river basin, covering a total area of 1739 km 2 with its main watercourse of 90 km length. The model is perform...

Arid and semi-arid areas of the world are confronted with limited water resources and rainfall patterns that initiate flush floods and severe erosion events. The simulation of the flood events of such systems requires high frequency meteorological data and accuracy and precision of geospatial data. In this paper the streamflow of a semi-arid river,...

The runoff in small insular catchments in the Mediterranean experiences high fluctuation depending mostly on the precipitation seasonality. These water bodies are important and can be more significant in the future due to climate change since significant alteration in rainfall (up to 35% rainfall reduction) and temperature increase (3–5 °C) by 2071...

Flooding of urban areas and extended river plumes in the coastal area are caused often during extreme precipitation events. The parameters of the flood frequency analysis are essential in the flood design and engineering protection works. The objective of this study is to compare different methods to derive frequency distributions of floods of an u...

The directive 2008/105/EC suggests the use of sediment or biota matrix for long-term monitoring of specific priority pollutants that tend to accumulate. But, the intermittent nature of flow in the majority of the Mediterranean rivers results in large variability of biological communities and especially fish, making advantageous the examination of p...

The main aim of this research was to improve risk mapping of heavy metals by taking account of erosion effects. A new spatiotemporal index, namely the G2met index, is introduced, with integration of pre-existing methodologies (Hakanson, EPM, and G2). The G2met index is depicted as a series of risk maps for each heavy metal on a month-time step. The...