Assessment of flood hazard areas at a regional scale using an index-based approach and Analytical Hierarchy Process: Application in Rhodope–Evros region, Greece

AbstractThe present study introduces a multi-criteria index to assess flood hazard areas in a regional scale. Accordingly, a Flood Hazard Index (FHI) has been defined and a spatial analysis in a GIS environment has been applied for the estimation of its value.The developed methodology processes information of seven parameters namely flow accumulation, distance from the drainage network, elevation, land use, rainfall intensity and geology. The initials of these criteria gave the name to the developed method: “FIGUSED”. The relative importance of each parameter for the occurrence and severity of flood has been connected to weight values. These values are calculated following an “Analytical Hierarchy Process”, a method originally developed for the solution of Operational Research problems. According to their weight values, information of the different parameters is superimposed, resulting to flood hazard mapping. The accuracy of the method has been supported by a sensitivity analysis that examines a range for the weights' values and corresponding to alternative scenarios.The presented methodology has been applied to an area in north-eastern Greece, where recurring flood events have appeared. Initially FIGUSED method resulted to a Flood Hazard Index (FHI) and a corresponding flood map. A sensitivity analysis on the parameters' values revealed some interesting information on the relative importance of each criterion, presented and commented in the Discussion section. Moreover, the sensitivity analysis concluded to a revised index FHIS (methodology named FIGUSED-S) and flood mapping, supporting the robustness of FIGUSED methodology. A comparison of the outcome with records of historical flood events confirmed that the proposed methodology provides valid results

Global patterns of nitrate isotope composition in rivers and adjacent aquifers reveal reactive nitrogen cascading

Remediation of nitrate pollution of Earth’s rivers and aquifers is hampered by cumulative biogeochemical processes and nitrogen sources. Isotopes (δ15N, δ18O) help unravel spatiotemporal nitrogen(N)-cycling of aquatic nitrate (NO3−). We synthesized nitrate isotope data (n = ~5200) for global rivers and shallow aquifers for common patterns and processes. Rivers had lower median NO3− (0.3 ± 0.2 mg L−1, n = 2902) compared to aquifers (5.5 ± 5.1 mg L−1, n = 2291) and slightly lower δ15N values (+7.1 ± 3.8‰, n = 2902 vs +7.7 ± 4.5‰, n = 2291), but were indistinguishable in δ18O (+2.3 ± 6.2‰, n = 2790 vs +2.3 ± 5.4‰, n = 2235). The isotope composition of NO3− was correlated with water temperature revealing enhanced N-cascading in warmer climates. Seasonal analyses revealed higher δ15N and δ18O values in wintertime, suggesting waste-related N-source signals are better preserved in the cold seasons. Isotopic assays of nitrate biogeochemical transformations are key to understanding nitrate pollution and to inform beneficial agricultural and land management strategies

Delineation of Suitable Zones for the Application of Managed Aquifer Recharge (MAR) in Coastal Aquifers Using Quantitative Parameters and the Analytical Hierarchy Process

Coastal aquifer salinization is usually related to groundwater overexploitation and water table decline. Managed Aquifer Recharge (MAR) can be applied as a measure to reverse and prevent this phenomenon. A detailed literature review was performed to identify the various methods and parameters commonly used to determine suitable sites of MAR application. Based on the review results, a new multi-criteria index (SuSAM) that is compatible to coastal aquifers was developed to delineate suitable zones for MAR application. New parameters were introduced into the index, such as distance from the shore and hydraulic resistance of the vadose zone, while factor weights were determined using the Analytical Hierarchy Process (AHP) and single sensitivity analysis. The applicability of the new index was examined in the coastal aquifer of the Anthemountas basin located in northern Greece. The most suitable areas for MAR application cover 28% of the aquifer’s surface area, while 16% of the area was characterized as non-suitable for MAR application. The new method constitutes the first step of the managed aquifer recharge concept for the delineation of MAR-suitable zones in coastal aquifers

Assessing groundwater pollution risk in Anthemountas basin, Northern Greece

The aim of this Ph.D. thesis is the assessment of groundwater pollution risk in Anthemountas river basin which covers an area of 374,69 km², and has a permanent population of 56.217 inhabitants. It is drained by a well-developed hydrographic network which is classified in the sixth class. The main river is Anthemountas without permanent flow. The relief is high hills - semi-mountainous with mean altitude and slope 259.3 m and 20%, respectively. The mountainous part of the basin consists of ophiolitic, crystalline and carbonate rocks, while the lowlands consist of Neogene and Quaternary sediments representing the 65% of the formations. Palaiozoic rocks are extremely fissured while the study area is characterized by intense neotectonic activity with Anthemountas fault as the most important fault. The main aquifer systems is developed within the neogene and quaternary deposits of confined and/or unconfined conditions, while the aquifers in fissured rocks are locally in fault zones. Human activities and overexploitation of groundwater are responsible for nitrate pollution and seawater intrusion respectively, while heavy metals (As, Fe, Cr) occurrence in groundwater can be associated with the geothermal fluids, clay minerals and ophiolitic rocks. Vertical seawater intrusion is detected from geoelectrical tomographies in the coastal area. Furthermore, the vadose zone media is determined from vertical electrical soundings as well as the porosity and hydraulic conductivity of aquifer system. Groundwater vulnerability is estimated with DRASTIC and AVI method, while DRASTIC PESTICIDE, GALDIT and LOS methods were used for the specific vulnerability assessment of pesticides, seawater intrusion and nitrogen pollution respectively. DRASTIC method is modified to estimate specific vulnerability for nitrates and pollution risk. Areas with high and very high values of pollution risk are found in the center of Galatista basin, southwest of Agia Triada and locally in Vasilika-Risio-Thermi sub-system. A coastal zone ranging from 4 km in Agia Triada to 9 km in N. Raidestos was estimated with median to high vulnerability to seawater intrusion.Στόχος της παρούσας Διδακτορικής Διατριβής είναι η εκτίμηση της διακινδύνευσης στην εξωτερική ρύπανση των υπόγειων νερών της λεκάνης του Ανθεμούντα. Η περιοχή έρευνας καταλαμβάνει έκταση 374,69 km², υπάγεται διοικητικά στην περιφέρεια Κεντρικής Μακεδονίας και έχει μόνιμο πληθυσμό 56,217 κατοίκους. Αποστραγγίζεται από καλά ανεπτυγμένο υδρογραφικό δίκτυο και μεγαλύτερο ποταμό τον Ανθεμούντα όπου τα τελευταία χρόνια δεν έχει μόνιμη ροή. Στην περιοχή έρευνας εκτεταμένη υδροφορία συναντάται εντός των ιζημάτων στους πορώδεις υδροφορείς, ενώ στα διερρηγμένα πετρώματα είναι τοπική κυρίως σε ζώνες διάρρηξης. Από την υδροχημική έρευνα προέκυψε ότι τα σημαντικότερα ποιοτικά προβλήματα της περιοχής είναι η νιτρορύπανση που οφείλεται σε ανθρώπινες δραστηριότητες, η διείσδυση του θαλασσινού νερού ως απόρροια των υπεραντλήσεων, τα γεωθερμικά ρευστά που ανέρχονται από τα ρήγματα και αναμειγνύονται με τους επιφανειακούς ψυχρούς υδροφορείς και η παρουσία υψηλών συγκεντρώσεων βαρέων μετάλλων. Το αρσενικό σχετίζεται με τη γεωθερμική δραστηριότητα της περιοχής, ενώ ο σίδηρος με την παρουσία συγκεκριμένων αργιλικών ορυκτών. Το εξασθενές χρώμιο στο υπόγειο νερό, όπως προέκυψε από την ορυκτολογική έρευνα, είναι λιθογενούς προέλευσης. Με βάση τις γεωφυσικές διασκοπήσεις που πραγματοποιήθηκαν, εντοπίστηκε η κατακόρυφη διείσδυση του θαλασσινού νερού στο παράκτιο τμήμα, προσδιορίστηκε το υλικό της ακόρεστης ζώνης, ενώ υπολογίστηκε και το ολικό πορώδες των υδροφορέων και ο συντελεστής της υδραυλικής αγωγιμότητας. Εκτιμήθηκε η ιδιοτρωτότητα των υδροφορέων με τις μεθόδους DRASTIC και AVI, η ειδική τρωτότητα στα φυτοφάρμακα με την παραλλαγή PESTICIDE της μεθόδου DRASTIC, στη διείσδυση του θαλασσινού νερού με τη μέθοδο GALDIT και η ειδική τρωτότητα του εδάφους στις απώλειες νιτρικών και νερού με τους δείκτες της μεθόδου LOS. Τροποποιήθηκε η μέθοδος DRASTIC για την εκτίμηση της ειδικής τρωτότητας στα νιτρικά ιόντα, ενώ εκτιμήθηκε τόσο η γενική διακινδύνευση των υπόγειων νερών στην εξωτερική ρύπανση, όσο και η ειδική στα νιτρικά. Τα αποτελέσματα έδειξαν ότι η υψηλή διακινδύνευση των υπόγειων νερών στα νιτρικά εντοπίζεται στο κέντρο της Γαλάτιστας, στα νοτιοδυτικά της Αγίας Τριάδας και κατά τόπους στην περιοχή μεταξύ Βασιλικών-Ρυσίου-Θέρμης. Τέλος, μέση έως υψηλή διακινδύνευση στη διείσδυση του θαλασσινού νερού εντοπίζεται από το παράκτιο τμήμα μέχρι και απόσταση 9 km προς το κέντρο της λεκάνης στην περιοχή της Νέας Ραιδεστού

Preventing Groundwater Pollution Using Vulnerability and Risk Mapping: The Case of the Florina Basin, NW Greece

The alluvial aquifer system of the Florina basin (320 km2) in North Greece is a representative area where irrigated agriculture is applied. Groundwater is the main source of water. The highest and mean nitrate concentrations in groundwater are 67.9 mg/L and 25 mg/L, respectively. High values could be associated with the use of nitrogen fertilizers from agricultural activities. This study deals with the evaluation of the groundwater quality. For this reason, hydrochemical analyses from 29 groundwater samples and water level measurements were performed for the wet and dry periods of 2016. The suitability of groundwater quality for irrigation purposes is examined by using different indices (Chlorinity Index, SAR, Sodium Percentage, Potential Salinity and Kelly’s index). In addition, the DRASTIC method was modified by using statistical methods, land use map and nitrate concentrations and applied in order to assess the groundwater vulnerability to external pollution. Notably, there was no correlation between the standard DRASTIC method and nitrate concentrations. However, the modified version and the obtained risk map showed high correlation with nitrate concentrations (ρ = 0.55) and the Groundwater Quality; hence, it is suggested as the base for a protection plan of the alluvial aquifer

Assessment of Groundwater Vulnerability in the North Aquifer Area of Rhodes Island Using the GALDIT Method and GIS

Salinization of coastal aquifer systems constitutes a major threat for groundwater. Especially areas with high population density due to increasing tourist activity may face severe problems. In this study, the GALDIT method was applied in the north side of Rhodes Island, Greece, in order to assess groundwater vulnerability to seawater intrusion. Hydrogeological data were elaborated in geographical information systems (GIS), and appropriate thematic maps were produced. The final vulnerability map was obtained from the combination of the thematic maps using overlying techniques. Based on the application of the GALDIT method, a zone up to 1000 m from the shore is characterized by medium to high vulnerability, while medium vulnerability characterizes the eastern part of the study area. Overexploitation of the aquifer, due to the intense touristic activity in Ialysos area, constitutes the main reason for groundwater salinization due to seawater intrusion in the study area. Consequently, planning of proper groundwater management and systematic monitoring of the groundwater reserves are of the utmost importance in order to solve existing problems and prevent future issues of salinization

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Not AvailableWater quality evaluation is critically important for the protection and sustainable management of groundwater resources, which are variably vulnerable to ever-increasing human-induced physical and chemical pressures (e.g., overexploitation and pollution of aquifers) and to climate change/variability. Preceding studies have applied a variety of tools and techniques, ranging from conventional to modern, for characterization of the groundwater quality worldwide. Recently, geographic information system (GIS) technology has been successfully integrated with the advanced statistical/geostatistical methods, providing improved interpretation capabilities for the assessment of the water quality over different spatial scales. This review intends to examine the current standing of the GIS-integrated statistical/geostatistical methods applied in hydrogeochemical studies. In this paper, we focus on applications of the time series modeling, multivariate statistical/geostatistical analyses, and artificial intelligence techniques used for groundwater quality evaluations and aquifer vulnerability assessments. In addition, we provide an overview of salient groundwater quality indices developed over the years and employed for the assessment of groundwater quality across the globe. Then, limitations and research gaps of the past studies are outlined and perspectives of the future research needs are discussed. It is revealed that comprehensive applications of the GIS-integrated applications of the advanced statistical methods are generally rare in groundwater quality evaluations. One of the major challenges in future research will be implementing procedures of statistical methods in GIS software to enhance analysis capabilities for both spatial and temporal data (multiple sites/stations and time frames) in a simultaneous manner.Not Availabl

Enhanced Characterization of the Krania–Elassona Structure and Functioning Allogenic Karst Aquifer in Central Greece

The present study highlights the importance of geological, hydrogeological, and hydrogeochemical characterization of a karst aquifer in building a conceptual model of the system. The karst system of Krania-Elassona in central Greece was chosen for this application. Hydrogeological research included geological mapping and hydrogeological analysis. Additionally, hydrochemical analysis of water samples was performed in boreholes, rivers, and the system's main spring. The Krania-Elassona aquifer consists of three horizons of marbles and is characterized by mature karstification. The karst aquifer is characterized by allogenic recharge mainly from the River Deskatis that accounts for up to 92% of the total flow. Groundwater and spring water are generally characterized as good quality and are suitable for irrigation and domestic use. The water type of the spring water is classified as Mg-HCO3. The application of a SARIMA (Seasonal Autoregressive Integrated Moving Average Model) model verified the conceptual model and successfully simulated spring discharge for a two-year period. The results of this study highlight the importance of basic hydrogeological research and the initial conceptualization of karst systems in reliably assessing groundwater vulnerability and modeling

A Hybrid GIS and AHP Approach for Modelling Actual and Future Forest Fire Risk Under Climate Change Accounting Water Resources Attenuation Role

Forest wildfires usually occur due to natural processes such as lightning and volcanic eruptions, but at the same time they are also an effect of uncontrolled and illegal anthropogenic activities. Different factors can influence forest wildfires, like the type of vegetation, morphology, climate, and proximity to human activities. A precise evaluation of forest fire issues and of the countermeasures needed to limit their impact could be satisfactory especially when forest fire risk (FFR) mapping is available. Here, we proposed an FFR evaluation methodology based on Geographic Information System (GIS) and the analytic hierarchy process (AHP). The study area is the Campania region (Southern Italy) that, for the last 30 years, has been affected by numerous wildfires. The proposed methodology analyzed 12 factors, and AHP was used for weight assignment, offering a new approach to some parameters. The method divided the study area into five risk classes, from very low to very high. Validation with fire alerts showed a good correlation between observed and predicted fires (0.79 R2). Analyzing the climate projections, a future FFR for 2040 was also assessed. The proposed methodology represents a reliable screening tool to identify areas under forest fire risk, and can help authorities to direct preventive actions

Management and Research Strategies of Karst Aquifers in Greece: Literature Overview and Exemplification Based on Hydrodynamic Modelling and Vulnerability Assessment of a Strategic Karst Aquifer

Karst aquifers are valuable water resources in terms of quantity and quality, hence, their protection and rational management is of utmost importance to sustain water supply. An overview of research articles regarding Karst aquifers in Greece was obtained revealing that progressively the initial simple statistical analysis was replaced from advanced tools but rarely coupled. Additionally, a combined approach including the concept of groundwater vulnerability and pollution risk in conjunction with statistical and hydrodynamic analysis was performed in the complex karst aquifer of Damasi-Titanos in Thessaly Central Greece. The karst aquifer discharges via three springs and it is in dynamic interaction with one of the two rivers that cross the system. The water demands of the area are mainly met with groundwater from the karst aquifer rendering its protection fundamental priority for the sustainability of the area. The hydrodynamic analysis of the karst system was performed by pairing statistical techniques and KarstMod. The analysis revealed a high correlation between the springs that highlights the karstification maturity of the aquifer. Additionally, spring discharge is mainly controlled by the percolation of River Titarisios rather than precipitation. Following the hydrodynamic analysis, the PaPRIKa method was applied and validated using sensitivity analysis in order to assess the intrinsic vulnerability. The vulnerability and hazard maps were combined to produce the pollution risk map of the karst aquifer. The majority of the karst aquifer is characterized by high to very high vulnerability as well as pollution risk. The case study and the obtained overview revealed that a holistic approach can provide mutually supported results increasing their reliability. In this base, a four-step road map including hydrogeological observation, statistical analysis, modelling and vulnerability assessment is suggested in order to obtain the sustainable exploration and integrated management of karst aquifers in Greece