Conventionally droughts are studied in terms of their dimensions (severity, duration and areal ex... more Conventionally droughts are studied in terms of their dimensions (severity, duration and areal extent), without specifying the affected system. The paper presents an innovative system-based approach for drought analysis, which can lead to rational decisions for combating drought. Concepts of water scarcity (drought, water shortage, aridity and desertification) are viewed within the perspective of this new approach. The paper focuses also on operational water management in the presence of drought. Starting from the needs for such management, the affected system is defined and the related quantities are identified. Also, subsystems are considered which allow the establishment of the link between specific variables
Climatic changes in a geographical area may be detected by examining long timeseries of precipita... more Climatic changes in a geographical area may be detected by examining long timeseries of precipitation and potential evapotranspiration. From the point of view of water resources management, both of these variables influence directly the water availability and water demand, and therefore represent the climatic conditions of the studied area effectively. However, to avoid misinterpretations or non interpreted trends of these variables, simultaneous analysis of trends through a single index, incorporating both variables, is needed. The paper proposes the Reconnaissance Drought Index (RDI) (initial or normalised expressions) as a single climatic index for the detection of possible climatic changes. Using data for various reference periods (12, 6, 3 months) seasonal changes can be also detected. The merits of such an approach are presented in this contribution and examples using RDI as a climatic index are also illustrated.
Preventive Maintenance for Water Utility Networks (PM4WAT) is a European Project which develops a... more Preventive Maintenance for Water Utility Networks (PM4WAT) is a European Project which develops an innovative web-based platform and courseware for Vocational Education and Training (VET) on state of the art practice on preventive maintenance of urban water utility networks. The project aims at improved maintenance, increased reliability and decreased disruption of service. The proposed training programme involves: (a) a theoretical part, which includes web-based courseware that covers the principles of preventive maintenance for water utilities including the benefits, the limitations and the organisational aspects, and (b) a practical part, which involves a system that integrates a Geographical Information System, Reliability Analysis and Database Queries to compute how ageing and natural hazards affect the reliability of a network under different environmental conditions. The system offers the trainee suggestions on the best way to rehabilitate the network under study. Among the o...
Drought indices have been devised for identification of drought and characterization of its sever... more Drought indices have been devised for identification of drought and characterization of its severity. Using drought indices, the duration, intensity and areal extent for each drought episode can be defined. They can be used to describe all types of droughts (that is meteorological drought, hydrological drought, agricultural droughts and socioeconomic drought). According to the type of drought, the appropriate drought index is selected. Drought indices are composite numerical figures incorporating mainly values of hydrometeorological indicators. The most popular drought indices presented in the report and applied in the participating countries in the MEDROPLAN project include the SPI, the PDSI, the method of Deciles, the recently developed RDI and others. Crucial elements in the procedure for calculating drought severity by using drought indices are the time step adopted and the threshold of each index selected. During the project a common methodology for applying drought indices for monitoring and assessment of droughts and estimation of drought risk was devised and applied to all case studies.
Drought is conventionally expressed as meteorological, hydrological and agricultural, dependent o... more Drought is conventionally expressed as meteorological, hydrological and agricultural, dependent on the affected system and the variables used in the analysis. The main dimensions of the meteorological drought, apart from severity, are the duration of the event and the spatial extent of the affected area. The study presented in this paper attempts to perform frequency analysis for the pairs severity-duration and severity-areal extent, using 2D-Archimedean Copulas. The Gumbel-Hougaard, the Clayton and the Frank families of copulas have been tested. The proposed methodology is applied to the eastern part of the island of CreteGreece. The area under study is divided in 1328 squares of 4 km each. The sample of 30 years of precipitation and temperature data from 9 meteorological stations is reproduced 9 times. The Reconnaissance Drought Index is used for estimating the severity of each drought event. The duration is represented by the number of years under drought, whereas the areal exten...
Climatic changes in a geographical area may be detected by examining long timeseries of precipita... more Climatic changes in a geographical area may be detected by examining long timeseries of precipitation and potential evapotranspiration. From the point of view of water resources management, both of these variables influence directly the water availability and water demand, and therefore represent the climatic conditions of the studied area effectively. However, to avoid misinterpretations or non interpreted trends of these variables, simultaneous analysis of trends through a single index, incorporating both variables, is needed. The paper proposes the Reconnaissance Drought Index (RDI) (initial or normalised expressions) as a single climatic index for the detection of possible climatic changes. Using data for various reference periods (12, 6, 3 months) seasonal changes can be also detected. The merits of such an approach are presented in this contribution and examples using RDI as a climatic index are also illustrated.
Preventive Maintenance for Water Utility Networks (PM4WAT) is a European Project which develops a... more Preventive Maintenance for Water Utility Networks (PM4WAT) is a European Project which develops an innovative web-based platform and courseware for Vocational Education and Training (VET) on state of the art practice on preventive maintenance of urban water utility networks. The project aims at improved maintenance, increased reliability and decreased disruption of service. The proposed training programme involves: (a) a theoretical part, which includes web-based courseware that covers the principles of preventive maintenance for water utilities including the benefits, the limitations and the organisational aspects, and (b) a practical part, which involves a system that integrates a Geographical Information System, Reliability Analysis and Database Queries to compute how ageing and natural hazards affect the reliability of a network under different environmental conditions. The system offers the trainee suggestions on the best way to rehabilitate the network under study. Among the o...
Drought indices have been devised for identification of drought and characterization of its sever... more Drought indices have been devised for identification of drought and characterization of its severity. Using drought indices, the duration, intensity and areal extent for each drought episode can be defined. They can be used to describe all types of droughts (that is meteorological drought, hydrological drought, agricultural droughts and socioeconomic drought). According to the type of drought, the appropriate drought index is selected. Drought indices are composite numerical figures incorporating mainly values of hydrometeorological indicators. The most popular drought indices presented in the report and applied in the participating countries in the MEDROPLAN project include the SPI, the PDSI, the method of Deciles, the recently developed RDI and others. Crucial elements in the procedure for calculating drought severity by using drought indices are the time step adopted and the threshold of each index selected. During the project a common methodology for applying drought indices for monitoring and assessment of droughts and estimation of drought risk was devised and applied to all case studies.
Drought is conventionally expressed as meteorological, hydrological and agricultural, dependent o... more Drought is conventionally expressed as meteorological, hydrological and agricultural, dependent on the affected system and the variables used in the analysis. The main dimensions of the meteorological drought, apart from severity, are the duration of the event and the spatial extent of the affected area. The study presented in this paper attempts to perform frequency analysis for the pairs severity-duration and severity-areal extent, using 2D-Archimedean Copulas. The Gumbel-Hougaard, the Clayton and the Frank families of copulas have been tested. The proposed methodology is applied to the eastern part of the island of CreteGreece. The area under study is divided in 1328 squares of 4 km each. The sample of 30 years of precipitation and temperature data from 9 meteorological stations is reproduced 9 times. The Reconnaissance Drought Index is used for estimating the severity of each drought event. The duration is represented by the number of years under drought, whereas the areal exten...
Drought is a natural hazard characterised mainly by three dimensions: severity, duration and area... more Drought is a natural hazard characterised mainly by three dimensions: severity, duration and areal extent. Although several simplifications were proposed for the analysis of droughts for assisting water managers and policy makers to address this complex phenomenon, drought severity remains the key factor for the characterisation of drought. Drought severity is conventionally assessed by drought indices, which are simple or composite indicators useful for identifying and monitoring drought events in a meaningful way. The paper reports on a specialised software package, named DrinC (Drought Indices Calculator), which was developed aiming at providing a simple interface for the calculation of drought indices, with emphasis on two recently developed indices, the Reconnaissance Drought Index (RDI) and the Streamflow Drought Index (SDI). The software can also be used for the calculation of the Standardised Precipitation Index (SPI) and the Rainfall Deciles. Additionally, DrinC includes a ...
Drought is a natural hazard characterised mainly by three dimensions: severity, duration and area... more Drought is a natural hazard characterised mainly by three dimensions: severity, duration and areal extent. Although several simplifications were proposed for the analysis of droughts for assisting water managers and policy makers to address this complex phenomenon, drought severity remains the key factor for the characterisation of drought. Drought severity is conventionally assessed by drought indices, which are simple or composite indicators useful for identifying and monitoring drought events in a meaningful way. The paper reports on a specialised software package, named DrinC (Drought Indices Calculator), which was developed aiming at providing a simple interface for the calculation of drought indices, with emphasis on two recently developed indices, the Reconnaissance Drought Index (RDI) and the Streamflow Drought Index (SDI). The software can also be used for the calculation of the Standardised Precipitation Index (SPI) and the Rainfall Deciles. Additionally, DrinC includes a ...
Both strategic and operational plans to face drought and water shortage need a mechanism way to a... more Both strategic and operational plans to face drought and water shortage need a mechanism way to assess the consequences so that the rational decisions are taken by water authorities and stakeholders. The paper presents a simplified methodology for assessing the vulnerability of each simple water system towards single and multi-year drought events. The proposed methodology is based on the assumption that the aggregated vulnerability function is of a multiplicative type. The paper also proposes the “annualised risk” as the key determinant to assess drought severity.
Conventionally droughts are studied in terms of their dimensions (severity, duration and areal ex... more Conventionally droughts are studied in terms of their dimensions (severity, duration and areal extent), without specifying the affected system. The paper presents an innovative system-based approach for drought analysis, which can lead to rational decisions for combating drought. Concepts of water scarcity (drought, water shortage, aridity and desertification) are viewed within the perspective of this new approach. The paper focuses also on operational water management in the presence of drought. Starting from the needs for such management, the affected system is defined and the related quantities are identified. Also, subsystems are considered which allow the establishment of the link between specific variables
Climatic changes in a geographical area may be detected by examining long timeseries of precipita... more Climatic changes in a geographical area may be detected by examining long timeseries of precipitation and potential evapotranspiration. From the point of view of water resources management, both of these variables influence directly the water availability and water demand, and therefore represent the climatic conditions of the studied area effectively. However, to avoid misinterpretations or non interpreted trends of these variables, simultaneous analysis of trends through a single index, incorporating both variables, is needed. The paper proposes the Reconnaissance Drought Index (RDI) (initial or normalised expressions) as a single climatic index for the detection of possible climatic changes. Using data for various reference periods (12, 6, 3 months) seasonal changes can be also detected. The merits of such an approach are presented in this contribution and examples using RDI as a climatic index are also illustrated.
Preventive Maintenance for Water Utility Networks (PM4WAT) is a European Project which develops a... more Preventive Maintenance for Water Utility Networks (PM4WAT) is a European Project which develops an innovative web-based platform and courseware for Vocational Education and Training (VET) on state of the art practice on preventive maintenance of urban water utility networks. The project aims at improved maintenance, increased reliability and decreased disruption of service. The proposed training programme involves: (a) a theoretical part, which includes web-based courseware that covers the principles of preventive maintenance for water utilities including the benefits, the limitations and the organisational aspects, and (b) a practical part, which involves a system that integrates a Geographical Information System, Reliability Analysis and Database Queries to compute how ageing and natural hazards affect the reliability of a network under different environmental conditions. The system offers the trainee suggestions on the best way to rehabilitate the network under study. Among the o...
Drought indices have been devised for identification of drought and characterization of its sever... more Drought indices have been devised for identification of drought and characterization of its severity. Using drought indices, the duration, intensity and areal extent for each drought episode can be defined. They can be used to describe all types of droughts (that is meteorological drought, hydrological drought, agricultural droughts and socioeconomic drought). According to the type of drought, the appropriate drought index is selected. Drought indices are composite numerical figures incorporating mainly values of hydrometeorological indicators. The most popular drought indices presented in the report and applied in the participating countries in the MEDROPLAN project include the SPI, the PDSI, the method of Deciles, the recently developed RDI and others. Crucial elements in the procedure for calculating drought severity by using drought indices are the time step adopted and the threshold of each index selected. During the project a common methodology for applying drought indices for monitoring and assessment of droughts and estimation of drought risk was devised and applied to all case studies.
Drought is conventionally expressed as meteorological, hydrological and agricultural, dependent o... more Drought is conventionally expressed as meteorological, hydrological and agricultural, dependent on the affected system and the variables used in the analysis. The main dimensions of the meteorological drought, apart from severity, are the duration of the event and the spatial extent of the affected area. The study presented in this paper attempts to perform frequency analysis for the pairs severity-duration and severity-areal extent, using 2D-Archimedean Copulas. The Gumbel-Hougaard, the Clayton and the Frank families of copulas have been tested. The proposed methodology is applied to the eastern part of the island of CreteGreece. The area under study is divided in 1328 squares of 4 km each. The sample of 30 years of precipitation and temperature data from 9 meteorological stations is reproduced 9 times. The Reconnaissance Drought Index is used for estimating the severity of each drought event. The duration is represented by the number of years under drought, whereas the areal exten...
Climatic changes in a geographical area may be detected by examining long timeseries of precipita... more Climatic changes in a geographical area may be detected by examining long timeseries of precipitation and potential evapotranspiration. From the point of view of water resources management, both of these variables influence directly the water availability and water demand, and therefore represent the climatic conditions of the studied area effectively. However, to avoid misinterpretations or non interpreted trends of these variables, simultaneous analysis of trends through a single index, incorporating both variables, is needed. The paper proposes the Reconnaissance Drought Index (RDI) (initial or normalised expressions) as a single climatic index for the detection of possible climatic changes. Using data for various reference periods (12, 6, 3 months) seasonal changes can be also detected. The merits of such an approach are presented in this contribution and examples using RDI as a climatic index are also illustrated.
Preventive Maintenance for Water Utility Networks (PM4WAT) is a European Project which develops a... more Preventive Maintenance for Water Utility Networks (PM4WAT) is a European Project which develops an innovative web-based platform and courseware for Vocational Education and Training (VET) on state of the art practice on preventive maintenance of urban water utility networks. The project aims at improved maintenance, increased reliability and decreased disruption of service. The proposed training programme involves: (a) a theoretical part, which includes web-based courseware that covers the principles of preventive maintenance for water utilities including the benefits, the limitations and the organisational aspects, and (b) a practical part, which involves a system that integrates a Geographical Information System, Reliability Analysis and Database Queries to compute how ageing and natural hazards affect the reliability of a network under different environmental conditions. The system offers the trainee suggestions on the best way to rehabilitate the network under study. Among the o...
Drought indices have been devised for identification of drought and characterization of its sever... more Drought indices have been devised for identification of drought and characterization of its severity. Using drought indices, the duration, intensity and areal extent for each drought episode can be defined. They can be used to describe all types of droughts (that is meteorological drought, hydrological drought, agricultural droughts and socioeconomic drought). According to the type of drought, the appropriate drought index is selected. Drought indices are composite numerical figures incorporating mainly values of hydrometeorological indicators. The most popular drought indices presented in the report and applied in the participating countries in the MEDROPLAN project include the SPI, the PDSI, the method of Deciles, the recently developed RDI and others. Crucial elements in the procedure for calculating drought severity by using drought indices are the time step adopted and the threshold of each index selected. During the project a common methodology for applying drought indices for monitoring and assessment of droughts and estimation of drought risk was devised and applied to all case studies.
Drought is conventionally expressed as meteorological, hydrological and agricultural, dependent o... more Drought is conventionally expressed as meteorological, hydrological and agricultural, dependent on the affected system and the variables used in the analysis. The main dimensions of the meteorological drought, apart from severity, are the duration of the event and the spatial extent of the affected area. The study presented in this paper attempts to perform frequency analysis for the pairs severity-duration and severity-areal extent, using 2D-Archimedean Copulas. The Gumbel-Hougaard, the Clayton and the Frank families of copulas have been tested. The proposed methodology is applied to the eastern part of the island of CreteGreece. The area under study is divided in 1328 squares of 4 km each. The sample of 30 years of precipitation and temperature data from 9 meteorological stations is reproduced 9 times. The Reconnaissance Drought Index is used for estimating the severity of each drought event. The duration is represented by the number of years under drought, whereas the areal exten...
Drought is a natural hazard characterised mainly by three dimensions: severity, duration and area... more Drought is a natural hazard characterised mainly by three dimensions: severity, duration and areal extent. Although several simplifications were proposed for the analysis of droughts for assisting water managers and policy makers to address this complex phenomenon, drought severity remains the key factor for the characterisation of drought. Drought severity is conventionally assessed by drought indices, which are simple or composite indicators useful for identifying and monitoring drought events in a meaningful way. The paper reports on a specialised software package, named DrinC (Drought Indices Calculator), which was developed aiming at providing a simple interface for the calculation of drought indices, with emphasis on two recently developed indices, the Reconnaissance Drought Index (RDI) and the Streamflow Drought Index (SDI). The software can also be used for the calculation of the Standardised Precipitation Index (SPI) and the Rainfall Deciles. Additionally, DrinC includes a ...
Drought is a natural hazard characterised mainly by three dimensions: severity, duration and area... more Drought is a natural hazard characterised mainly by three dimensions: severity, duration and areal extent. Although several simplifications were proposed for the analysis of droughts for assisting water managers and policy makers to address this complex phenomenon, drought severity remains the key factor for the characterisation of drought. Drought severity is conventionally assessed by drought indices, which are simple or composite indicators useful for identifying and monitoring drought events in a meaningful way. The paper reports on a specialised software package, named DrinC (Drought Indices Calculator), which was developed aiming at providing a simple interface for the calculation of drought indices, with emphasis on two recently developed indices, the Reconnaissance Drought Index (RDI) and the Streamflow Drought Index (SDI). The software can also be used for the calculation of the Standardised Precipitation Index (SPI) and the Rainfall Deciles. Additionally, DrinC includes a ...
Both strategic and operational plans to face drought and water shortage need a mechanism way to a... more Both strategic and operational plans to face drought and water shortage need a mechanism way to assess the consequences so that the rational decisions are taken by water authorities and stakeholders. The paper presents a simplified methodology for assessing the vulnerability of each simple water system towards single and multi-year drought events. The proposed methodology is based on the assumption that the aggregated vulnerability function is of a multiplicative type. The paper also proposes the “annualised risk” as the key determinant to assess drought severity.
The aim of the present work is to provide a simplified but reliable methodology for the estimatio... more The aim of the present work is to provide a simplified but reliable methodology for the estimation of urban flood hazard, based on a hydrologic-hydraulic model and by utilizing Multi-Criteria Decision Analysis (MCDA). A number of manholes are ranked as to their vulnerability to flood on the basis of two different MCDA methods and the relative results are compared. The methodology proposed herein is demonstrated in a part of a subcatchment of a combined drainage network, in Athens, Greece, but it is easy to be implemented in other, both rural and urban, basins. The nodes of the drainage system that are most vulnerable to flood are determined based on eight indices: (i) conveyance (calculated using Manning equation for conduits) (m3/s); (ii) subcatchment area (m2); (iii) subcatchment width (m); (iv) subcatchment average slope (%); (v) manning coefficient of the impervious part of the subcatchment (s/m1/3); (vi) Manning coefficient of the pervious part of the subcatchment (s/m1/3); (vii) impervious area of the subcatchment (%); and (viii) SCS runoff Curve Number. Four manholes (alternatives) are evaluated with respect to the aforementioned indices (evaluation criteria) as to their vulnerability to flood. The manholes are ranked from the most “risky” to the less “risky”. To this end, two different MCDA methods are applied, the Weighted Summation method and the Electre II method, while criteria weights are estimated by using the Analytic Hierarchy Process (AHP) and the respective Saaty scale (Saaty, 1977). Both Weighted Summation and Electre II are discrete quantitative methods dealing with quantitative data on the basis of alternative consequences and priorities (weights) assigned to the evaluation criteria (Janssen, 1992).
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Papers by H. Vangelis
The nodes of the drainage system that are most vulnerable to flood are determined based on eight indices: (i) conveyance (calculated using Manning equation for conduits) (m3/s); (ii) subcatchment area (m2); (iii) subcatchment width (m); (iv) subcatchment average slope (%); (v) manning coefficient of the impervious part of the subcatchment (s/m1/3); (vi) Manning coefficient of the pervious part of the subcatchment (s/m1/3); (vii) impervious area of the subcatchment (%); and (viii) SCS runoff Curve Number.
Four manholes (alternatives) are evaluated with respect to the aforementioned indices (evaluation criteria) as to their vulnerability to flood. The manholes are ranked from the most “risky” to the less “risky”. To this end, two different MCDA methods are applied, the Weighted Summation method and the Electre II method, while criteria weights are estimated by using the Analytic Hierarchy Process (AHP) and the respective Saaty scale (Saaty, 1977). Both Weighted Summation and Electre II are discrete quantitative methods dealing with quantitative data on the basis of alternative consequences and priorities (weights) assigned to the evaluation criteria (Janssen, 1992).