Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation, 2007
Modelling in support of an interdisciplinary approach to ecosystem restitution. This paper report... more Modelling in support of an interdisciplinary approach to ecosystem restitution. This paper reports on a study being undertaken to analyze the potential effects of rewetting when undertaken for the restitution of the catchment ecosystem of the Grote Nete catchment. In bringing together the expertise of both ecological and hydrological modelers, this study aims at ensuring that the science being performed is immediately relevant from both the environmental management and the socio-political perspectives. Like many European catchments, Grote Nete has been experiencing an increase in extreme hydrological events. In addition, there has been a decline in the ecological value of the catchment ecosystem. The problem is considered to be a confl ict of interests arising between urban/agricultural and nature conservation needs. Rewetting has been considered as a possible intervention to reverse these trends. However, a shortcoming with rewetting is that the hydrological consequences remain largely unknown. A numerical model has been developed to study these potential effects. A land use model, SPAN was developed and coupled to a physically-based, fully distributed model (MIKE SHE) to complete an ecohydrological model. The paper describes the development of the model.
ABSTRACT Urbanization and especially impervious areas, in combination with wastewater treatment i... more ABSTRACT Urbanization and especially impervious areas, in combination with wastewater treatment infrastructure, can exert several pressures on the hydrological cycle. These pressures were studied for the Grote Nete catchment in Belgium (8.18% impervious area and 3.89% effective impervious area), based on a combination of empirical and model-based approaches. The effective impervious area, combined with the extent of the wastewater collection regions which do not coincide with the natural catchment boundaries, was used as an indicator for the urbanization pressure. Our study revealed changes in the total upstream areas of the subcatchments between -16% and +3%, and in upstream impervious areas between -99% and +64%. These changes lead to important inter-catchment water transfers. Based on simulations with a physically-based and spatially-distributed hydrological catchment model, profound impacts of effective impervious area on infiltration and runoff were found. The model results show that the changes in impervious areas and related water displacements in and between catchments due to the installation of the wastewater treatment infrastructure severely impacted low flows, peak flows and seasonal trends. They moreover show that it is difficult, but of utmost importance, to incorporate these pressures and artificial processes in an accurate way during the development of hydrological models for urbanized catchments.
It is shown how Model Predictive Control can be used for flood control of river systems modelled ... more It is shown how Model Predictive Control can be used for flood control of river systems modelled with real data. A linear model for the Demer, a river in Belgium, is derived, which is used inside the optimisation problem solved by the controller. This optimisation problem is formulated such that the controller can be used for set-point and flood control. A Kalman filter is used as a state estimator. Closed loop simulations performed with a full hydrodynamic model of the Demer in combination with historical rainfall data show that the proposed control scheme outperforms the current control strategy.
Models used for climate change impact projections are typically not tested for simulation beyond ... more Models used for climate change impact projections are typically not tested for simulation beyond current climate conditions. Since we have no data truly reflecting future conditions, a key challenge in this respect is to rigorously test models using proxies of future conditions. This paper presents a validation framework and guiding principles applicable across earth science disciplines for testing the capability of models to project future climate change and its impacts. Model test schemes comprising split-sample tests, differential splitsample tests and proxy site tests are discussed in relation to their application for projections by use of single models, ensemble modelling and space-time-substitution and in relation to use of Climatic Change
Communications in Computer and Information Science, 2010
Drawing on the authors' involvement in a European Union Erasmus project, this paper explores a ne... more Drawing on the authors' involvement in a European Union Erasmus project, this paper explores a new holistic approach to climate change education which uses as a source of active/social learning and knowledge construction the diversity of different disciplinary and sectoral approaches. We further argue for a corresponding pedagogy based on developing transboundary competences where the communicative engagement across space and time, and between diverse perspectives and standpoints, is ICT-enabled. Meeting these challenges is a normative goal, not only for this expanded interdisciplinary approach to climate change education, but also for a global resolution of the climate change issue itself.
Drawing on the authors’ involvement in a European Union Erasmus project, this paper explores a ne... more Drawing on the authors’ involvement in a European Union Erasmus project, this paper explores a new holistic approach to climate change education which uses as a source of active/social learning and knowledge construction the diversity of different disciplinary and sectoral approaches. We further argue for a corresponding pedagogy based on developing transboundary competences where the communicative engagement across space and time, and between diverse perspectives and standpoints, is ICT-enabled. Meeting these challenges is a normative goal, not only for this expanded interdisciplinary approach to climate change education, but also for a global resolution of the climate change issue itself.
This paper reports on a project to compare predictions from a range of catchment models applied t... more This paper reports on a project to compare predictions from a range of catchment models applied to a mesoscale river basin in central Germany and to assess various ensemble predictions of catchment streamflow. The models encompass a large range in inherent complexity and input requirements. In approximate order of decreasing complexity, they are DHSVM, MIKE-SHE, TOPLATS, WASIM-ETH, SWAT, PRMS, SLURP, HBV, LASCAM and IHACRES. The models are calibrated twice using different sets of input data. The two predictions from each model are then combined by simple averaging to produce a singlemodel ensemble. The 10 resulting single-model ensembles are combined in various ways to produce multi-model ensemble predictions. Both the single-model ensembles and the multi-model ensembles are shown to give predictions that are generally superior to those of their respective constituent models, both during a 7-year calibration period and a 9-year validation period. This occurs despite a considerable disparity in performance of the individual models. Even the weakest of models is shown to contribute useful information to the ensembles they are part of. The best model combination methods are a trimmed mean (constructed using the central four or six predictions each day) and a weighted mean ensemble (with weights calculated from calibration performance) that places relatively large weights on the better performing models. Conditional ensembles, in which separate model weights are used in different system states (e.g. summer and winter, high and low flows) generally yield little improvement over the weighted mean ensemble. However a conditional ensemble that discriminates between rising and receding flows shows moderate improvement. An analysis of ensemble predictions shows that the best ensembles are not necessarily those containing the best individual models. Conversely, it appears that some models that predict well individually do not necessarily combine well with other models in multi-model ensembles. The reasons behind these observations may relate to the effects of the weighting schemes, non-stationarity of the climate series and possible cross-correlations between models.
Ensemble modelling, whereby predictions from several models are pooled in an attempt to improve p... more Ensemble modelling, whereby predictions from several models are pooled in an attempt to improve prediction accuracy, has often been used in the climate and atmospheric sciences, but until recently, has received little attention in hydrology. One of the key aims of the ensemble approach is to reduce uncertainty in the modelled predictions. This paper reports on a project to compare predictions from a range of catchment models applied to a mesoscale river basin in central Germany and to produce ensemble predictions of the effects of several projected land use changes. The models encompass a large range in inherent complexity and input requirements. In approximate order of decreasing complexity, they are DHSVM, MIKE-SHE, TOPLATS, WASIM-ETH, SWAT, PRMS, SLURP, HBV, LAS-CAM and IHACRES.
ABSTRACT Coastal floodplains are complex regions that form the interface between human, physical ... more ABSTRACT Coastal floodplains are complex regions that form the interface between human, physical and natural systems. This paper describes the development, application and evaluation of a conceptual foundation for quantitative integrated floodplain risk assessments using the recently-developed SPR systems model. The SPR systems model is a conceptual model that combines the well-established Source–Pathway–Receptor (SPR) approach with the concept of system diagrams. In comparison to the conventional approach, the systems model provides spatially explicit quasi-2D descriptions of the floodplain in terms of constituent elements and possible element linkages. The quasi-2D SPR, as it will henceforth be referred to in this paper, is not the final product of this work, but is an important intermediate stage which has been pursued as part of a wider European flood risk project THESEUS (www.theseusproject.eu). Further research is currently on-going to provide full quantification of the quasi-2D SPR, and to add further refinements such that hydraulic assessments could follow on easily and rapidly from the results of these appraisals. The first part of the paper synthesises current conceptual treatment of coastal floodplains and identifies areas for improvement in describing coastal floodplains as complex systems. The synthesis demonstrates that the conceptual foundation of a ‘typical’ flood risk study often achieves a less comprehensive and integrated description of the floodplain than the quantitative models which it informs. From this synthesis, the quasi-2D SPR is identified as a more robust and informative conceptual foundation for an integrated risk assessment. The quasi-2D SPR has been applied to seven European coastal floodplains as part of the THESEUS project. The second part of the paper discusses in detail the application of the quasi-2D SPR to three contrasting floodplain systems — an estuary, a coastal peninsula and a mixed open coast/estuary site. The quasi-2D SPR provides a consistent approach for achieving comprehensive floodplain descriptions that are individual to each coastal floodplain. These are obtained through a robust, participatory model-building exercise, that facilitates developing a shared understanding of the system. The constructed model is a powerful tool for structuring and integrating existing knowledge across multiple disciplines. Applications of the quasi-2D SPR provide key insights into the characteristics of complex coastal floodplains — insights that will inform the quantification process. Finally, the paper briefly describes the on-going quantitative extension to the quasi-2D SPR.
This paper examines the sensitivity and uncertainty of evaporation estimates from Nasser Lake, so... more This paper examines the sensitivity and uncertainty of evaporation estimates from Nasser Lake, south of Egypt using data collected at the floating station Raft, 2 km upstream of the Aswan High Dam, and 12 evaporation models. Based on their approach the evaporation models were ranked in five classes, respectively the Bowen ratio energy budget (BREB) approach, three energy-aerodynamic based methods, a mass transfer method, two temperature and five solar radiation-temperature approaches. State dependent parameter models were used to estimate the sensitivity indices of the different evaporation estimation methods at daily and monthly frequencies. A drastic reduction in the cost of the sensitivity analysis was obtained when coupled with efficient sampling methods, producing quasi-Monte Carlo sequences (Latin Hypercube samples). Analysis of the sensitivity indices (S i ) revealed that the energy and advective parameters (Q x and Q v ) in the Bowen ratio energy budget method most strongly affect evaporation estimates. The most sensitive parameters for the energy-aerodynamic methods (Penman, Priestley-Taylor and the deBruin-Keijman methods) are the change in heat storage (Q x ) and solar radiation. For the other methods the most sensitive parameters were solar radiation, air temperature and vapour pressure, but with lower sensitivities. After investigation of the first and second-order sensitivity indices, it was found that the first-order sensitivity indices capture more than 90% of the total variance of the evaporation estimates. Interactions between input parameters were found limited with a maximum contribution to variance of less than 3.3% for daily frequency and less than 8.5% for the monthly frequency. Results indicated that many parameters in the 12 evaporation models could be fixed without appreciably affecting the output of these models. This helped to reduce the computational load of these models. The uncertainty results show that the Dalton group is subject to the highest error. The overall uncertainty ranged from 9% (BREB method) to 15% (mass transfer method) of the mean evaporation rate.
Coastal floodplains are complex regions that form the interface between human, physical and natur... more Coastal floodplains are complex regions that form the interface between human, physical and natural systems. This paper describes the development, application and evaluation of a conceptual foundation for quantitative integrated floodplain risk assessments using the recently-developed SPR systems model. The SPR systems model is a conceptual model that combines the well-established Source-Pathway-Receptor (SPR) approach with the concept of system diagrams. In comparison to the conventional approach, the systems model provides spatially explicit quasi-2D descriptions of the floodplain in terms of constituent elements and possible element linkages. The quasi-2D SPR, as it will henceforth be referred to in this paper, is not the final product of this work, but is an important intermediate stage which has been pursued as part of a wider European flood risk project THESEUS (www.theseusproject.eu). Further research is currently on-going to provide full quantification of the quasi-2D SPR, and to add further refinements such that hydraulic assessments could follow on easily and rapidly from the results of these appraisals. The first part of the paper synthesises current conceptual treatment of coastal floodplains and identifies areas for improvement in describing coastal floodplains as complex systems. The synthesis demonstrates that the conceptual foundation of a 'typical' flood risk study often achieves a less comprehensive and integrated description of the floodplain than the quantitative models which it informs. From this synthesis, the quasi-2D SPR is identified as a more robust and informative conceptual foundation for an integrated risk assessment. The quasi-2D SPR has been applied to seven European coastal floodplains as part of the THESEUS project. The second part of the paper discusses in detail the application of the quasi-2D SPR to three contrasting floodplain systemsan estuary, a coastal peninsula and a mixed open coast/estuary site. The quasi-2D SPR provides a consistent approach for achieving comprehensive floodplain descriptions that are individual to each coastal floodplain. These are obtained through a robust, participatory model-building exercise, that facilitates developing a shared understanding of the system. The constructed model is a powerful tool for structuring and integrating existing knowledge across multiple disciplines. Applications of the quasi-2D SPR provide key insights into the characteristics of complex coastal floodplainsinsights that will inform the quantification process. Finally, the paper briefly describes the on-going quantitative extension to the quasi-2D SPR.
Journal of environmental biology / Academy of Environmental Biology, India, 2012
Variations in lake evaporation have a significant impact on the energy and water budgets of lakes... more Variations in lake evaporation have a significant impact on the energy and water budgets of lakes. Understanding these variations and the role of climate is important for water resources management as well as predicting future changes in lake hydrology as a result of climate change. This study presents a comprehensive, 10-year analysis of seasonal, intraseasonal, and interannual variations in lake evaporation for Lake Nasser in South Egypt. Meteorological and lake temperature measurements were collected from an instrumented platform (Raft floating weather station) at 2 km upstream ofthe Aswan High Dam. In addition to that, radiation measurements at three locations on the lake: Allaqi, Abusembel and Arqeen (respectively at 75, 280 and 350 km upstream of the Aswan High Dam) are used. The data were analyzed over 14-day periods from 1995 to 2004 to provide bi-weekly energy budget estimates of evaporation rate. The mean evaporation rate for lake Nasser over the study period was 5.88 mm d...
This study focuses on the empirical statistical analysis of the anomalies in daily precipitation ... more This study focuses on the empirical statistical analysis of the anomalies in daily precipitation extremes by applying the quantile perturbation method (QPM) to data from 31 Iranian weather stations during the period between 1961 and 2005. The possible causes behind the anomalies in precipitation extremes are identified by analyzing their relationship with the anomalies in eight atmospheric indices (i.e., NAO, SOI, PDO, AMO, NCP, DMI, WeMO, SSN). In terms of decadal oscillations, the country was generally wet in the 1960s and 1970s with most stations exhibiting periods of higher quantile perturbations, whereas lower quantile perturbations were dominant in the 1980s and 1990s. The highest perturbation in extreme precipitation quantiles prevails in Central Iran during the early 1980s, in which the quantiles are about 50% higher than the ones based on the full time series. The frequency of significant precipitation anomalies for winter season was greater than that for spring and autumn seasons. For the summer season, the humid region in North Iran demonstrates strong positive anomalies. The results highlight the noticeable role of large-scale climatic factors in the anomalous behavior of precipitation extremes in Iran. The atmospheric drivers of the quantile anomalies in extreme precipitation were found to differ from one season to another.
ABSTRACT It is common practice to use a 30-year period to derive climatological values, as recomm... more ABSTRACT It is common practice to use a 30-year period to derive climatological values, as recommended by the World Meteorological Organization. However this convention relies on important assumptions, of which the validity can be examined by deriving the uncertainty inherent to using a limited time-period for deriving climatological values. In this study a new method, aiming at deriving this uncertainty, has been developed with an application to precipitation for a station in Europe (Westdorpe) and one in Africa (Gulu). The weather generator framework is used to produce synthetic daily precipitation time-series that can also be regarded as alternative climate realizations. The framework consists of an improved Markov model, which shows good performance in reproducing the 5-day precipitation variability. The sub-seasonal, seasonal and the inter-annual signals are introduced in the weather generator framework by including covariates. These covariates are derived from an empirical mode decomposition analysis with an improved stability and significance assessment. Introducing covariates was found to substantially improve the monthly precipitation variability for Gulu. From the weather generator, 1,000 synthetic time-series were produced. The divergence between these time-series demonstrates an uncertainty, inherent to using a 30-year period for mean precipitation, of 11 % for Westdorpe and 15 % for Gulu. The uncertainty for precipitation 10-year return levels was found to be 37 % for both sites.
Extreme precipitation events have attracted a great deal of attention among the scientific commun... more Extreme precipitation events have attracted a great deal of attention among the scientific community because of their devastating consequences on human livelihood and socio-economic development. To assess changes in precipitation extremes in a given region, it is essential to analyze decadal oscillations in precipitation extremes. This study examines temporal oscillations in precipitation data in several subregions of Iran using a novel quantile perturbation method during 1980–2010. Precipitation data from NASA’s Modern-Era Retrospective Analysis for Research and Applications-Land (MERRA-Land) are used in this study. The results indicate significant anomalies in precipitation extremes in the northwest and southeast regions of Iran. Analysis of extreme precipitation perturbations reveals that perturbations for the monthly aggregation level are generally lower than the annual perturbations. Furthermore, high-oscillation and low-oscillation periods are found in extreme precipitation quantiles across different seasons. In all selected regions, a significant anomaly (i.e., extreme wet/dry conditions) in precipitation extremes is observed during spring.
Communications in Computer and Information Science, 2010
Drawing on the authors' involvement in a European Union Erasmus project, this paper explores a ne... more Drawing on the authors' involvement in a European Union Erasmus project, this paper explores a new holistic approach to climate change education which uses as a source of active/social learning and knowledge construction the diversity of different disciplinary and sectoral approaches. We further argue for a corresponding pedagogy based on developing transboundary competences where the communicative engagement across space and time, and between diverse perspectives and standpoints, is ICT-enabled. Meeting these challenges is a normative goal, not only for this expanded interdisciplinary approach to climate change education, but also for a global resolution of the climate change issue itself.
Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation, 2007
Modelling in support of an interdisciplinary approach to ecosystem restitution. This paper report... more Modelling in support of an interdisciplinary approach to ecosystem restitution. This paper reports on a study being undertaken to analyze the potential effects of rewetting when undertaken for the restitution of the catchment ecosystem of the Grote Nete catchment. In bringing together the expertise of both ecological and hydrological modelers, this study aims at ensuring that the science being performed is immediately relevant from both the environmental management and the socio-political perspectives. Like many European catchments, Grote Nete has been experiencing an increase in extreme hydrological events. In addition, there has been a decline in the ecological value of the catchment ecosystem. The problem is considered to be a confl ict of interests arising between urban/agricultural and nature conservation needs. Rewetting has been considered as a possible intervention to reverse these trends. However, a shortcoming with rewetting is that the hydrological consequences remain largely unknown. A numerical model has been developed to study these potential effects. A land use model, SPAN was developed and coupled to a physically-based, fully distributed model (MIKE SHE) to complete an ecohydrological model. The paper describes the development of the model.
ABSTRACT Urbanization and especially impervious areas, in combination with wastewater treatment i... more ABSTRACT Urbanization and especially impervious areas, in combination with wastewater treatment infrastructure, can exert several pressures on the hydrological cycle. These pressures were studied for the Grote Nete catchment in Belgium (8.18% impervious area and 3.89% effective impervious area), based on a combination of empirical and model-based approaches. The effective impervious area, combined with the extent of the wastewater collection regions which do not coincide with the natural catchment boundaries, was used as an indicator for the urbanization pressure. Our study revealed changes in the total upstream areas of the subcatchments between -16% and +3%, and in upstream impervious areas between -99% and +64%. These changes lead to important inter-catchment water transfers. Based on simulations with a physically-based and spatially-distributed hydrological catchment model, profound impacts of effective impervious area on infiltration and runoff were found. The model results show that the changes in impervious areas and related water displacements in and between catchments due to the installation of the wastewater treatment infrastructure severely impacted low flows, peak flows and seasonal trends. They moreover show that it is difficult, but of utmost importance, to incorporate these pressures and artificial processes in an accurate way during the development of hydrological models for urbanized catchments.
It is shown how Model Predictive Control can be used for flood control of river systems modelled ... more It is shown how Model Predictive Control can be used for flood control of river systems modelled with real data. A linear model for the Demer, a river in Belgium, is derived, which is used inside the optimisation problem solved by the controller. This optimisation problem is formulated such that the controller can be used for set-point and flood control. A Kalman filter is used as a state estimator. Closed loop simulations performed with a full hydrodynamic model of the Demer in combination with historical rainfall data show that the proposed control scheme outperforms the current control strategy.
Models used for climate change impact projections are typically not tested for simulation beyond ... more Models used for climate change impact projections are typically not tested for simulation beyond current climate conditions. Since we have no data truly reflecting future conditions, a key challenge in this respect is to rigorously test models using proxies of future conditions. This paper presents a validation framework and guiding principles applicable across earth science disciplines for testing the capability of models to project future climate change and its impacts. Model test schemes comprising split-sample tests, differential splitsample tests and proxy site tests are discussed in relation to their application for projections by use of single models, ensemble modelling and space-time-substitution and in relation to use of Climatic Change
Communications in Computer and Information Science, 2010
Drawing on the authors' involvement in a European Union Erasmus project, this paper explores a ne... more Drawing on the authors' involvement in a European Union Erasmus project, this paper explores a new holistic approach to climate change education which uses as a source of active/social learning and knowledge construction the diversity of different disciplinary and sectoral approaches. We further argue for a corresponding pedagogy based on developing transboundary competences where the communicative engagement across space and time, and between diverse perspectives and standpoints, is ICT-enabled. Meeting these challenges is a normative goal, not only for this expanded interdisciplinary approach to climate change education, but also for a global resolution of the climate change issue itself.
Drawing on the authors’ involvement in a European Union Erasmus project, this paper explores a ne... more Drawing on the authors’ involvement in a European Union Erasmus project, this paper explores a new holistic approach to climate change education which uses as a source of active/social learning and knowledge construction the diversity of different disciplinary and sectoral approaches. We further argue for a corresponding pedagogy based on developing transboundary competences where the communicative engagement across space and time, and between diverse perspectives and standpoints, is ICT-enabled. Meeting these challenges is a normative goal, not only for this expanded interdisciplinary approach to climate change education, but also for a global resolution of the climate change issue itself.
This paper reports on a project to compare predictions from a range of catchment models applied t... more This paper reports on a project to compare predictions from a range of catchment models applied to a mesoscale river basin in central Germany and to assess various ensemble predictions of catchment streamflow. The models encompass a large range in inherent complexity and input requirements. In approximate order of decreasing complexity, they are DHSVM, MIKE-SHE, TOPLATS, WASIM-ETH, SWAT, PRMS, SLURP, HBV, LASCAM and IHACRES. The models are calibrated twice using different sets of input data. The two predictions from each model are then combined by simple averaging to produce a singlemodel ensemble. The 10 resulting single-model ensembles are combined in various ways to produce multi-model ensemble predictions. Both the single-model ensembles and the multi-model ensembles are shown to give predictions that are generally superior to those of their respective constituent models, both during a 7-year calibration period and a 9-year validation period. This occurs despite a considerable disparity in performance of the individual models. Even the weakest of models is shown to contribute useful information to the ensembles they are part of. The best model combination methods are a trimmed mean (constructed using the central four or six predictions each day) and a weighted mean ensemble (with weights calculated from calibration performance) that places relatively large weights on the better performing models. Conditional ensembles, in which separate model weights are used in different system states (e.g. summer and winter, high and low flows) generally yield little improvement over the weighted mean ensemble. However a conditional ensemble that discriminates between rising and receding flows shows moderate improvement. An analysis of ensemble predictions shows that the best ensembles are not necessarily those containing the best individual models. Conversely, it appears that some models that predict well individually do not necessarily combine well with other models in multi-model ensembles. The reasons behind these observations may relate to the effects of the weighting schemes, non-stationarity of the climate series and possible cross-correlations between models.
Ensemble modelling, whereby predictions from several models are pooled in an attempt to improve p... more Ensemble modelling, whereby predictions from several models are pooled in an attempt to improve prediction accuracy, has often been used in the climate and atmospheric sciences, but until recently, has received little attention in hydrology. One of the key aims of the ensemble approach is to reduce uncertainty in the modelled predictions. This paper reports on a project to compare predictions from a range of catchment models applied to a mesoscale river basin in central Germany and to produce ensemble predictions of the effects of several projected land use changes. The models encompass a large range in inherent complexity and input requirements. In approximate order of decreasing complexity, they are DHSVM, MIKE-SHE, TOPLATS, WASIM-ETH, SWAT, PRMS, SLURP, HBV, LAS-CAM and IHACRES.
ABSTRACT Coastal floodplains are complex regions that form the interface between human, physical ... more ABSTRACT Coastal floodplains are complex regions that form the interface between human, physical and natural systems. This paper describes the development, application and evaluation of a conceptual foundation for quantitative integrated floodplain risk assessments using the recently-developed SPR systems model. The SPR systems model is a conceptual model that combines the well-established Source–Pathway–Receptor (SPR) approach with the concept of system diagrams. In comparison to the conventional approach, the systems model provides spatially explicit quasi-2D descriptions of the floodplain in terms of constituent elements and possible element linkages. The quasi-2D SPR, as it will henceforth be referred to in this paper, is not the final product of this work, but is an important intermediate stage which has been pursued as part of a wider European flood risk project THESEUS (www.theseusproject.eu). Further research is currently on-going to provide full quantification of the quasi-2D SPR, and to add further refinements such that hydraulic assessments could follow on easily and rapidly from the results of these appraisals. The first part of the paper synthesises current conceptual treatment of coastal floodplains and identifies areas for improvement in describing coastal floodplains as complex systems. The synthesis demonstrates that the conceptual foundation of a ‘typical’ flood risk study often achieves a less comprehensive and integrated description of the floodplain than the quantitative models which it informs. From this synthesis, the quasi-2D SPR is identified as a more robust and informative conceptual foundation for an integrated risk assessment. The quasi-2D SPR has been applied to seven European coastal floodplains as part of the THESEUS project. The second part of the paper discusses in detail the application of the quasi-2D SPR to three contrasting floodplain systems — an estuary, a coastal peninsula and a mixed open coast/estuary site. The quasi-2D SPR provides a consistent approach for achieving comprehensive floodplain descriptions that are individual to each coastal floodplain. These are obtained through a robust, participatory model-building exercise, that facilitates developing a shared understanding of the system. The constructed model is a powerful tool for structuring and integrating existing knowledge across multiple disciplines. Applications of the quasi-2D SPR provide key insights into the characteristics of complex coastal floodplains — insights that will inform the quantification process. Finally, the paper briefly describes the on-going quantitative extension to the quasi-2D SPR.
This paper examines the sensitivity and uncertainty of evaporation estimates from Nasser Lake, so... more This paper examines the sensitivity and uncertainty of evaporation estimates from Nasser Lake, south of Egypt using data collected at the floating station Raft, 2 km upstream of the Aswan High Dam, and 12 evaporation models. Based on their approach the evaporation models were ranked in five classes, respectively the Bowen ratio energy budget (BREB) approach, three energy-aerodynamic based methods, a mass transfer method, two temperature and five solar radiation-temperature approaches. State dependent parameter models were used to estimate the sensitivity indices of the different evaporation estimation methods at daily and monthly frequencies. A drastic reduction in the cost of the sensitivity analysis was obtained when coupled with efficient sampling methods, producing quasi-Monte Carlo sequences (Latin Hypercube samples). Analysis of the sensitivity indices (S i ) revealed that the energy and advective parameters (Q x and Q v ) in the Bowen ratio energy budget method most strongly affect evaporation estimates. The most sensitive parameters for the energy-aerodynamic methods (Penman, Priestley-Taylor and the deBruin-Keijman methods) are the change in heat storage (Q x ) and solar radiation. For the other methods the most sensitive parameters were solar radiation, air temperature and vapour pressure, but with lower sensitivities. After investigation of the first and second-order sensitivity indices, it was found that the first-order sensitivity indices capture more than 90% of the total variance of the evaporation estimates. Interactions between input parameters were found limited with a maximum contribution to variance of less than 3.3% for daily frequency and less than 8.5% for the monthly frequency. Results indicated that many parameters in the 12 evaporation models could be fixed without appreciably affecting the output of these models. This helped to reduce the computational load of these models. The uncertainty results show that the Dalton group is subject to the highest error. The overall uncertainty ranged from 9% (BREB method) to 15% (mass transfer method) of the mean evaporation rate.
Coastal floodplains are complex regions that form the interface between human, physical and natur... more Coastal floodplains are complex regions that form the interface between human, physical and natural systems. This paper describes the development, application and evaluation of a conceptual foundation for quantitative integrated floodplain risk assessments using the recently-developed SPR systems model. The SPR systems model is a conceptual model that combines the well-established Source-Pathway-Receptor (SPR) approach with the concept of system diagrams. In comparison to the conventional approach, the systems model provides spatially explicit quasi-2D descriptions of the floodplain in terms of constituent elements and possible element linkages. The quasi-2D SPR, as it will henceforth be referred to in this paper, is not the final product of this work, but is an important intermediate stage which has been pursued as part of a wider European flood risk project THESEUS (www.theseusproject.eu). Further research is currently on-going to provide full quantification of the quasi-2D SPR, and to add further refinements such that hydraulic assessments could follow on easily and rapidly from the results of these appraisals. The first part of the paper synthesises current conceptual treatment of coastal floodplains and identifies areas for improvement in describing coastal floodplains as complex systems. The synthesis demonstrates that the conceptual foundation of a 'typical' flood risk study often achieves a less comprehensive and integrated description of the floodplain than the quantitative models which it informs. From this synthesis, the quasi-2D SPR is identified as a more robust and informative conceptual foundation for an integrated risk assessment. The quasi-2D SPR has been applied to seven European coastal floodplains as part of the THESEUS project. The second part of the paper discusses in detail the application of the quasi-2D SPR to three contrasting floodplain systemsan estuary, a coastal peninsula and a mixed open coast/estuary site. The quasi-2D SPR provides a consistent approach for achieving comprehensive floodplain descriptions that are individual to each coastal floodplain. These are obtained through a robust, participatory model-building exercise, that facilitates developing a shared understanding of the system. The constructed model is a powerful tool for structuring and integrating existing knowledge across multiple disciplines. Applications of the quasi-2D SPR provide key insights into the characteristics of complex coastal floodplainsinsights that will inform the quantification process. Finally, the paper briefly describes the on-going quantitative extension to the quasi-2D SPR.
Journal of environmental biology / Academy of Environmental Biology, India, 2012
Variations in lake evaporation have a significant impact on the energy and water budgets of lakes... more Variations in lake evaporation have a significant impact on the energy and water budgets of lakes. Understanding these variations and the role of climate is important for water resources management as well as predicting future changes in lake hydrology as a result of climate change. This study presents a comprehensive, 10-year analysis of seasonal, intraseasonal, and interannual variations in lake evaporation for Lake Nasser in South Egypt. Meteorological and lake temperature measurements were collected from an instrumented platform (Raft floating weather station) at 2 km upstream ofthe Aswan High Dam. In addition to that, radiation measurements at three locations on the lake: Allaqi, Abusembel and Arqeen (respectively at 75, 280 and 350 km upstream of the Aswan High Dam) are used. The data were analyzed over 14-day periods from 1995 to 2004 to provide bi-weekly energy budget estimates of evaporation rate. The mean evaporation rate for lake Nasser over the study period was 5.88 mm d...
This study focuses on the empirical statistical analysis of the anomalies in daily precipitation ... more This study focuses on the empirical statistical analysis of the anomalies in daily precipitation extremes by applying the quantile perturbation method (QPM) to data from 31 Iranian weather stations during the period between 1961 and 2005. The possible causes behind the anomalies in precipitation extremes are identified by analyzing their relationship with the anomalies in eight atmospheric indices (i.e., NAO, SOI, PDO, AMO, NCP, DMI, WeMO, SSN). In terms of decadal oscillations, the country was generally wet in the 1960s and 1970s with most stations exhibiting periods of higher quantile perturbations, whereas lower quantile perturbations were dominant in the 1980s and 1990s. The highest perturbation in extreme precipitation quantiles prevails in Central Iran during the early 1980s, in which the quantiles are about 50% higher than the ones based on the full time series. The frequency of significant precipitation anomalies for winter season was greater than that for spring and autumn seasons. For the summer season, the humid region in North Iran demonstrates strong positive anomalies. The results highlight the noticeable role of large-scale climatic factors in the anomalous behavior of precipitation extremes in Iran. The atmospheric drivers of the quantile anomalies in extreme precipitation were found to differ from one season to another.
ABSTRACT It is common practice to use a 30-year period to derive climatological values, as recomm... more ABSTRACT It is common practice to use a 30-year period to derive climatological values, as recommended by the World Meteorological Organization. However this convention relies on important assumptions, of which the validity can be examined by deriving the uncertainty inherent to using a limited time-period for deriving climatological values. In this study a new method, aiming at deriving this uncertainty, has been developed with an application to precipitation for a station in Europe (Westdorpe) and one in Africa (Gulu). The weather generator framework is used to produce synthetic daily precipitation time-series that can also be regarded as alternative climate realizations. The framework consists of an improved Markov model, which shows good performance in reproducing the 5-day precipitation variability. The sub-seasonal, seasonal and the inter-annual signals are introduced in the weather generator framework by including covariates. These covariates are derived from an empirical mode decomposition analysis with an improved stability and significance assessment. Introducing covariates was found to substantially improve the monthly precipitation variability for Gulu. From the weather generator, 1,000 synthetic time-series were produced. The divergence between these time-series demonstrates an uncertainty, inherent to using a 30-year period for mean precipitation, of 11 % for Westdorpe and 15 % for Gulu. The uncertainty for precipitation 10-year return levels was found to be 37 % for both sites.
Extreme precipitation events have attracted a great deal of attention among the scientific commun... more Extreme precipitation events have attracted a great deal of attention among the scientific community because of their devastating consequences on human livelihood and socio-economic development. To assess changes in precipitation extremes in a given region, it is essential to analyze decadal oscillations in precipitation extremes. This study examines temporal oscillations in precipitation data in several subregions of Iran using a novel quantile perturbation method during 1980–2010. Precipitation data from NASA’s Modern-Era Retrospective Analysis for Research and Applications-Land (MERRA-Land) are used in this study. The results indicate significant anomalies in precipitation extremes in the northwest and southeast regions of Iran. Analysis of extreme precipitation perturbations reveals that perturbations for the monthly aggregation level are generally lower than the annual perturbations. Furthermore, high-oscillation and low-oscillation periods are found in extreme precipitation quantiles across different seasons. In all selected regions, a significant anomaly (i.e., extreme wet/dry conditions) in precipitation extremes is observed during spring.
Communications in Computer and Information Science, 2010
Drawing on the authors' involvement in a European Union Erasmus project, this paper explores a ne... more Drawing on the authors' involvement in a European Union Erasmus project, this paper explores a new holistic approach to climate change education which uses as a source of active/social learning and knowledge construction the diversity of different disciplinary and sectoral approaches. We further argue for a corresponding pedagogy based on developing transboundary competences where the communicative engagement across space and time, and between diverse perspectives and standpoints, is ICT-enabled. Meeting these challenges is a normative goal, not only for this expanded interdisciplinary approach to climate change education, but also for a global resolution of the climate change issue itself.
In order to comply with effluent standards, wastewater operators need to avoid hydraulic overload... more In order to comply with effluent standards, wastewater operators need to avoid hydraulic overloading of the wastewater treatment plant (WWTP), as this can result in the washout of activated sludge from secondary settling tanks. Hydraulic overloading can occur in a systematic way, for instance when sewer network connections are extended without increasing the WWTP's capacity accordingly. This study demonstrates the use of rule-based real-time control (RTC) to reduce the load to the WWTP while restricting the overall overflow volume of the sewer system to a minimum. Further, it shows the added value of RTC despite the limited availability of monitoring data and information on the catchment through a parsimonious simulation approach, using relocation of spatial system boundaries and creating required input data through reverse modelling. Focus was hereby on the accurate modelling of pump hydraulics and control. Finally, two different methods of global sensitivity analysis were employed to verify the influence of parameters of both the model and the implemented control algorithm. Both methods show the importance of good knowledge of the system properties, but that monitoring errors play a minor role.
Building conceptual sewer models can be a time-consuming task, especially for large or complex mo... more Building conceptual sewer models can be a time-consuming task, especially for large or complex models or models that require input data that might be difficult/tedious to obtain manually. This paper presents a semi-automated procedure for the buildup and calibration of one conceptual model that requires detailed input data such as throttle dimensions, pump curves or water level-storage relations. The procedure uses a hydrodynamic model as basis for sewer network data to create the model layout. A standardised series of composite rainfall events is applied to the hydrodynamic model in order to obtain the necessary reference data for the automated calibration of the conceptual model. Both model buildup and calibration are illustrated by means of a case study. Comparison of results of the hydrodynamic and conceptual model for a 1 year long-term series shows that the automated buildup and calibration can lead to an accurate conceptual model in short time.
While real-time control (RTC) is considered an established means of performance improvement for e... more While real-time control (RTC) is considered an established means of performance improvement for existing urban drainage networks, practical applications are frequently only documented for large case studies, and many operators are still reluctant to adopt RTC into their own systems. The purpose of the presented study is to highlight the potential of RTC also for smaller networks by the example of five representative catchments in Flanders, Belgium, and to demonstrate a novel methodology for the automated design of control strategies. This method analyses a given sewer network for the identification of suitable existing and new control locations. The gathered information is used in a second step for the design of control algorithms according to generic control concepts documented in the literature, such as e.g., "Equal Filling Degree". The resulting RTC strategy uses sensible default parameters, and can form a starting point for further refinement through optimization or manual tuning. With a modelled total combined sewer overflow volume reduction of 20 % to 50 %, the created strategies showed generally good performance for the tested catchments. The method proved to be applicable for all tested networks. Its use for the real-life implementation of RTC is currently under way for 10 other Flemish cases.
An extension of the frequently applied equal filling degree control algorithm is proposed for int... more An extension of the frequently applied equal filling degree control algorithm is proposed for integrated control of sewer system and wastewater treatment plant (WWTP). Under dry weather conditions (DWC), this control synchronizes sewer storage volume activation at pumping stations (PS) throughout the sewer system with the intermittent aeration at the WWTP. This is in contrast with the frequently advocated influent load equalization at WWTPs. The concept is demonstrated on a case study using an integrated system composed of detailed models for sewer system and WWTP where it reveals considerable potential for energy savings and effluent quality improvement. Moreover, the integrated control allows for the reduction of combined sewer overflows during wet weather events and decreased sedimentation potential in the sewer system. Neither weather predictions nor structural changes at the WWTP or in the sewer system are required. The control concept is applicable to about 50 Flemish WWTPs.
9th IWA Symposium on Systems Analysis and Integrated Assessment, 2015
In order to comply with the effluent norms, wastewater operators need to avoid hydraulic overload... more In order to comply with the effluent norms, wastewater operators need to avoid hydraulic overload of their wastewater treatment plants (WWTP), as this can entail the wash out of activated sludge from the secondary settling tanks. This can become a problem when extending existing transport infrastructure.
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Papers by P. Willems