40 research outputs found

    Numerical modeling for groundwater protection in the Venetian plain between the Brenta and Piave Rivers

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    The Ph.D. project tackled the scientific challenges that a water utility company in the northeast of Italy, Alto Trevigiano Servizi, must face in the elaboration of the Water Safety Plan (WSP), which is the most effective preventive tool to ensure good quality water and consumers health protection. The WSPs guidelines were defined by the World Health Organization and were subsequently implemented in a European Directive and Italian law. The thesis, after an introduction on the scientifical issues, started with the description of the work done to reproduce in CATHY the model that the PhD student Tommaso Trentin built using the software FeFlow. The study area has an extension of around 900 km2 and is delimited to the north-east by the Piave river, to the west side by a flow line parallel to the Brenta river, while the southern boundary is closed by the Risorgive area, and the North boundary by the Montello and colli Asolani. The north part is characterized by an undifferentiated aquifer, while the southern part hosts a multilayer system with 8 confined aquifers. Some modifications, e.g., the mesh refining, the sensitivity analysis, were implemented in the model to try to improve its performance. Also, the soil conductivity of the shallowest soil layer (1 m) was changed following the indications of Carta della permeabilità dei suoli from ARPAV site and the boundary conditions of the norther part of the domain were better defined. Before the calibration step, the initial mesh that hosts the multilayers systems of 8 aquitards and 8 aquifers was cut at the bottom of the first unconfined aquifer. This allowed to speed up the calibration and focus on the aquifer directly influenced by the atmospheric boundary conditions and subject to recharge variability. The calibration was performed alternating FePESt and CATHY. FePEST, having already implemented the PEST algorithm, allowed to easily implement the pilot points method that in CATHY would have require too much time. Both the bottom of the unconfined aquifer and the hydraulic conductivity field were calibrated. The improvement in terms of RMSE was relevant, the errors being reduced to 1/3. Once the calibrated model was obtained, also a validation step was performed. The resulting model allowed us to investigate an irrigation variation scenario, planned in compliance with the European directive indication, to save water: currently a large area of the domain is interested by flood irrigation considered no more sustainable, since it requires a large amount of water. The scenario considered a switch to sprinkler irrigation only. The results show a slight groundwater head decrease in the wells located in the area affected by the irrigation technique conversion. This result was confirmed by the difference of the total cumulative recharge over the domain in case of sprinkler and flood irrigation and sprinkler irrigation only. The model seems to be not particularly affected by the irrigation modification but more sensitive to the hydraulic conductivity values: a map of the mean distribution of the recharge shows that the larger fraction of the recharge occurs where hydraulic conductivity is larger. Parallelly to the continuation of this project, also a study on the analysis of numerical dispersion affecting CATHY model was carry out. This study will be useful for future simulations on vulnerability to contaminations that require an accurate solute transport modeling. Due to lack of time it was not possible to investigate the contaminants transport phenomenon in the area of study to accurately define the wells’ head protection areas, important part of the WSPs, but the preliminary results obtained from the model we built can be considered a good starting point for future transport studies.The Ph.D. project tackled the scientific challenges that a water utility company in the northeast of Italy, Alto Trevigiano Servizi, must face in the elaboration of the Water Safety Plan (WSP), which is the most effective preventive tool to ensure good quality water and consumers health protection. The WSPs guidelines were defined by the World Health Organization and were subsequently implemented in a European Directive and Italian law. The thesis, after an introduction on the scientifical issues, started with the description of the work done to reproduce in CATHY the model that the PhD student Tommaso Trentin built using the software FeFlow. The study area has an extension of around 900 km2 and is delimited to the north-east by the Piave river, to the west side by a flow line parallel to the Brenta river, while the southern boundary is closed by the Risorgive area, and the North boundary by the Montello and colli Asolani. The north part is characterized by an undifferentiated aquifer, while the southern part hosts a multilayer system with 8 confined aquifers. Some modifications, e.g., the mesh refining, the sensitivity analysis, were implemented in the model to try to improve its performance. Also, the soil conductivity of the shallowest soil layer (1 m) was changed following the indications of Carta della permeabilità dei suoli from ARPAV site and the boundary conditions of the norther part of the domain were better defined. Before the calibration step, the initial mesh that hosts the multilayers systems of 8 aquitards and 8 aquifers was cut at the bottom of the first unconfined aquifer. This allowed to speed up the calibration and focus on the aquifer directly influenced by the atmospheric boundary conditions and subject to recharge variability. The calibration was performed alternating FePESt and CATHY. FePEST, having already implemented the PEST algorithm, allowed to easily implement the pilot points method that in CATHY would have require too much time. Both the bottom of the unconfined aquifer and the hydraulic conductivity field were calibrated. The improvement in terms of RMSE was relevant, the errors being reduced to 1/3. Once the calibrated model was obtained, also a validation step was performed. The resulting model allowed us to investigate an irrigation variation scenario, planned in compliance with the European directive indication, to save water: currently a large area of the domain is interested by flood irrigation considered no more sustainable, since it requires a large amount of water. The scenario considered a switch to sprinkler irrigation only. The results show a slight groundwater head decrease in the wells located in the area affected by the irrigation technique conversion. This result was confirmed by the difference of the total cumulative recharge over the domain in case of sprinkler and flood irrigation and sprinkler irrigation only. The model seems to be not particularly affected by the irrigation modification but more sensitive to the hydraulic conductivity values: a map of the mean distribution of the recharge shows that the larger fraction of the recharge occurs where hydraulic conductivity is larger. Parallelly to the continuation of this project, also a study on the analysis of numerical dispersion affecting CATHY model was carry out. This study will be useful for future simulations on vulnerability to contaminations that require an accurate solute transport modeling. Due to lack of time it was not possible to investigate the contaminants transport phenomenon in the area of study to accurately define the wells’ head protection areas, important part of the WSPs, but the preliminary results obtained from the model we built can be considered a good starting point for future transport studies

    Realising Global Water Futures: a Summary of Progress in Delivering Solutions to Water Threats in an Era of Global Change

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    Canada First Research Excellence FundNon-Peer ReviewedOver the past six years the Global Water Futures program has produced a wide range of scientific findings and engagements with multiple types of potential users of the research. This briefing book provides a snapshot of some of the science advancements and user engagement that have taken place to date. Annual reports to the funding agency are the most up to date source of information: this compilation has been created from reports submitted by projects in 2022, representing both completed and current project work. The briefing book aims to provide quick access to information about GWF projects in a single place for GWF’s User Advisory Panel: we hope that knowing more about the research being produced will spark conversations about how to make the best use of the new knowledge in both policy and practice

    Analytical and Stochastic Numerical Methods for the Simulation of Subsurface Flow in Floodplains

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    Floodplain aquifers are important hydraulic connectors between hillslopes and surface-water bodies. The flow field in floodplain aquifers comprises different flow components governed by various geometric and hydrogeologic parameters. In this work, (semi-)analytical and numerical stochastic simulations are used to address three classical problems associated with investigations of floodplain aquifers. To this end, the Ammer floodplain west of TĂĽbingen serves as an exemplary study site. The first aspect of this dissertation focuses on valley-scale lateral hyporheic exchange in floodplain aquifers driven by widening and subsequent narrowing of the aquifer geometry. By means of a new semi-analytical solution, simple analytical proxy-models can be derived that allow a trivial and quick assessment, whether this type of exchange is relevant in a given setting. The application of these tools to the Ammer floodplain shows that the site has the geometric potential for notable valley-scale hyporheic exchange, but small hydraulic conductivities and lateral influxes from the hillslopes restrict the exchange zone to a negligible extent. The second topic is concerned with identifying promising points in space, where hydraulic-head information would help to locate groundwater divides separating the catchment area of floodplain aquifers from other catchments. A respective uncertainty-reduction optimization problem is formulated and solved by the application of a stochastic framework based on pre-filtered steady-state flow models. In the context of the Ammer floodplain, this analysis confirms that a presumed shift between groundwater and surface water divide is likely to exist. Three observation points identified by the procedure are predicted to help in reducing the related uncertainty by more than fifty percent. The third and final subject deals with calibrating steady-state floodplain models to hydraulic-head data. A modified, proxy-model-based, global calibration routine is able to find well-performing parameter sets that bring a steady-state Ammer floodplain model in agreement with measured field data. Neural Posterior Estimation, a technique from the field of Simulation-Based Inference, confirms these parameter sets and sheds light on the related uncertainties and correlations. A key result of this analysis is the confirmed inter-basin flow from the Ammer hillslopes to the Neckar valley, which takes place in the Erfurt formation beneath the Spitzberg ridge and the Wurmlingen saddle

    How a dry year affects spatial variability of ground thaw and changes the hydrology of a small Arctic watershed

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    The summer of 2021 in the Inuvik area, NWT was warm and dry. As recorded in Siksik Creek, a sub-catchment of Trail Valley Creek located 50 km north-east of Inuvik, this was the 7th warmest summer and driest July recorded to date. This presented a unique opportunity to study the drying phenomena of Arctic ecosystems. This is pertinent to the study of permafrost degradation, as the drying phenomena is still vastly understudied and there are few datasets available that record abnormally dry conditions in Arctic catchments. These data sets are needed to properly show the influence that this has on active layer thicknesses. It is unknown whether these conditions may pose a risk to permafrost, if this is spatially variable, and what other processes might amplify or hinder this. The main objective of this thesis is to explore how a dry year affects active layer thaw and the hydrology of Siksik Creek so that we may better understand how catchments such as Siksik will respond to ongoing climate change. To do this a mix of field results and modelling was used to show and quantify how these may affect active layer thaw as well as water balance components. The three main research chapters of this thesis divide this by analyzing active layer thaw as physically measured in the catchment to previous years, by using the model GEOtop to assess how this affects water balance components, and then by simulating wetter conditions to show the affect soil moisture has. Field data were collected from May 25th to August 29th in Siksik Creek during the summer of 2021, where the data collected included active layer thicknesses, depth to the water table, as well as stratigraphy and soil thicknesses across a variety of terrain type throughout the entirety of the catchment. This study specifically focused on measuring these data across hummocks and inter-hummocks throughout the catchment, as these features are ubiquitous in the Mackenzie uplands. In addition to analyzing the 2021 field data, the GEOtop physically based hydrology model was used to explore the processes controlling active layer thicknesses, water table depths, and various water balance components over the course of the summer of 2021. GEOtop is designed to handle microtopographies, such as hummocks and other terrain features. Further, we compare the physical and simulated results from the summer of 2021 to a more normal and wetter year (2016) to assess the differences that soil moisture has on the hydrology and active layer thaw of Siksik Creek. We explored how the movement of water impacted thaw depths in these landscapes, how spatial variability of thaw is influenced by soil moisture, and by the terrain features that control this. We found that peat thicknesses in this area are controlled by the presence of hummocks, where peat is thickest between hummock mounds in an area called the inter-hummock zone. This variability of peat thicknesses directly controls the spatial variability of soil moisture, and this had implications on thaw. In Chapter Two it was found that thaw for the summer of 2021 was shallower than expected in the inter-hummock zones by as much as 20cm compared to similar studies in Siksik and in similar landscapes in Alaska. This chapter also showed that the overlying vegetation, specifically lichens and mosses, were statistically linked to peat thicknesses representative of hummocks and inter-hummocks - where lichens tended to be overtop of hummocks, and mosses overtop of inter-hummocks. This correlation was then used with UAV imagery, taken in mid-June, to map mosses and lichens across the catchment and by proxy the locations of hummocks and inter-hummocks. This map was built into the model GEOtop to simulate Siksik Creek for the summer of 2021. Starting in Chapter Three, the modelled portion of this thesis covered a wide aspect of simulations, where the influence of hummocks was assessed, as well as shrubs and snow when they were added to the model, and finally assessing the role soil moisture plays within all of these various processes. It was found that hummocks, when they were specifically discretized and compared to a simple soil column, reached freshet and max discharge sooner by as much as two days, a lag that existed in the evapotranspiration outputs as well. However, these results were relatively consistent and the only major difference between these two simulations was seen in the 2d active layer depth maps. It was found that microtopography by the end of the summer seemed to influence local patterns of thaw more than larger topographical features such as natural depressions in the landscape did. When shrubs and snow were added to the model domain and simulated it was found that the presence of snow or lack thereof was the main component of difference in the discharge and evapotranspiration data. The active layer depth maps changed between simulations, with the shrub only simulations having the lowest degree of thaw, with a degree of variability seen between simulations. In comparison, the water table depths hardly changed between simulations, and it was hypothesized that the dryness of the summer and the lack of soil moisture was the main culprit for this. To test if this was the case, in Chapter Four, precipitation and snow water-equivalent data was taken from a wetter year (2016) and replaced the values for the dry summer of 2021. This was done so that only moisture available to the system was changed. It was found that soil moisture was in fact the main cause for this lack of variability. The wetter simulations because of this had deeper thaw throughout the catchment, with both the extent, max thaw depths, and min thaw depths increasing. The water table depths on the other hand became shallower and the ground surface was much more inundated with water. The spatial variability in the water table depth maps was found to match where the presence of taller shrubs in the catchment exist, where these areas had the least amount of soil moisture and the shallowest thaw depths. Whereas the areas with the highest amount of soil moisture content had the deepest thaw depths in the catchment. Overall, this thesis helps to improve our understanding of how peat catchments similar to Siksik Creek might respond to either the wetting or drying of the Arctic. This thesis also advances our understanding on the controls of soil moisture variability and ground thaw, as well as its spatial variability. One can infer from this study that for posterity it is the warm and wet summers rather than the warm and dry summers that pose the largest risk to permafrost and its degradation

    Controls on groundwater and surface water salinity in coastal Bangladesh

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    Salinity in surface water and groundwater is a pervasive issue along coastal Bangladesh, a low-lying megadelta where around 35 million people live. A large amount of this land has been reclaimed using a network of low-lying polders. The area is particularly susceptible to flooding from tropical cyclones. Cyclone induced storm surges coupled with the low-lying reclaimed land can breach polder embankments and cause extensive flooding, resulting in excess salinity in soil and surface water. Salinity in drinking water is known to cause adverse effects on human health. It is, therefore, important to identify the controls surface water and groundwater salinity in these coastal areas. A fully coupled surface-subsurface model of a coastal polder by using HydroGeo- Sphere is developed to investigate the impact of storm surge events on groundwater salinity. The hydrological parameters were calibrated from the fieldwork at a field site in the Dacope Upazila, in the southwest coastal region of Bangladesh. The results suggest that sudden salt fluxes in the pond are likely to build up salinity in the underlying sediment. A set of scenarios were considered: a cyclone induced storm surge during both the monsoon and dry seasons, and both with and without remediation. The results show that surge events caused a rise in salinity in drinking water and near-surface groundwater. However, rapid remediation after a surge event could help mitigate the severity of the impact on drinking water. This provides suggestions for water resources management planning. The 2D cross-section model was extended to the 3D model to improve the understanding of the salinity process. Climate change scenarios were then used to evaluate the effects of episodic cyclone surges on shallow groundwater salinity. This study suggests that more frequent cyclones would worsen not only salinity in near-surface groundwater but lateral saltwater intrusion at the shallow or deep aquifers.Open Acces

    Nature-based solutions efficiency evaluation against natural hazards: Modelling methods, advantages and limitations

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    Nature-based solutions (NBS) for hydro-meteorological risks (HMRs) reduction and management are becoming increasingly popular, but challenges such as the lack of well-recognised standard methodologies to evaluate their performance and upscale their implementation remain. We systematically evaluate the current state-of-the art on the models and tools that are utilised for the optimum allocation, design and efficiency evaluation of NBS for five HMRs (flooding, droughts, heatwaves, landslides, and storm surges and coastal erosion). We found that methods to assess the complex issue of NBS efficiency and cost-benefits analysis are still in the development stage and they have only been implemented through the methodologies developed for other purposes such as fluid dynamics models in micro and catchment scale contexts. Of the reviewed numerical models and tools MIKE-SHE, SWMM (for floods), ParFlow-TREES, ACRU, SIMGRO (for droughts), WRF, ENVI-met (for heatwaves), FUNWAVE-TVD, BROOK90 (for landslides), TELEMAC and ADCIRC (for storm surges) are more flexible to evaluate the performance and effectiveness of specific NBS such as wetlands, ponds, trees, parks, grass, green roof/walls, tree roots, vegetations, coral reefs, mangroves, sea grasses, oyster reefs, sea salt marshes, sandy beaches and dunes. We conclude that the models and tools that are capable of assessing the multiple benefits, particularly the performance and cost-effectiveness of NBS for HMR reduction and management are not readily available. Thus, our synthesis of modelling methods can facilitate their selection that can maximise opportunities and refute the current political hesitation of NBS deployment compared with grey solutions for HMR management but also for the provision of a wide range of social and economic co-benefits. However, there is still a need for bespoke modelling tools that can holistically assess the various components of NBS from an HMR reduction and management perspective. Such tools can facilitate impact assessment modelling under different NBS scenarios to build a solid evidence base for upscaling and replicating the implementation of NBS

    Nature-based solutions efficiency evaluation against natural hazards: modelling methods, advantages and limitations

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    Nature-based solutions (NBS) for hydro-meteorological risks (HMRs) reduction and management are becoming increasingly popular, but challenges such as the lack of well-recognised standard methodologies to evaluate their performance and upscale their implementation remain. We systematically evaluate the current state-of-the art on the models and tools that are utilised for the optimum allocation, design and efficiency evaluation of NBS for five HMRs (flooding, droughts, heatwaves, landslides, and storm surges and coastal erosion). We found that methods to assess the complex issue of NBS efficiency and cost-benefits analysis are still in the development stage and they have only been implemented through the methodologies developed for other purposes such as fluid dynamics models in micro and catchment scale contexts. Of the reviewed numerical models and tools MIKE-SHE, SWMM (for floods), ParFlow-TREES, ACRU, SIMGRO (for droughts), WRF, ENVI-met (for heatwaves), FUNWAVE-TVD, BROOK90 (for landslides), TELEMAC and ADCIRC (for storm surges) are more flexible to evaluate the performance and effectiveness of specific NBS such as wetlands, ponds, trees, parks, grass, green roof/walls, tree roots, vegetations, coral reefs, mangroves, sea grasses, oyster reefs, sea salt marshes, sandy beaches and dunes. We conclude that the models and tools that are capable of assessing the multiple benefits, particularly the performance and cost-effectiveness of NBS for HMR reduction and management are not readily available. Thus, our synthesis of modelling methods can facilitate their selection that can maximise opportunities and refute the current political hesitation of NBS deployment compared with grey solutions for HMR management but also for the provision of a wide range of social and economic co-benefits. However, there is still a need for bespoke modelling tools that can holistically assess the various components of NBS from an HMR reduction and management perspective. Such tools can facilitate impact assessment modelling under different NBS scenarios to build a solid evidence base for upscaling and replicating the implementation of NBS

    Integrated Environmental Modelling Framework for Cumulative Effects Assessment

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    Global warming and population growth have resulted in an increase in the intensity of natural and anthropogenic stressors. Investigating the complex nature of environmental problems requires the integration of different environmental processes across major components of the environment, including water, climate, ecology, air, and land. Cumulative effects assessment (CEA) not only includes analyzing and modeling environmental changes, but also supports planning alternatives that promote environmental monitoring and management. Disjointed and narrowly focused environmental management approaches have proved dissatisfactory. The adoption of integrated modelling approaches has sparked interests in the development of frameworks which may be used to investigate the processes of individual environmental component and the ways they interact with each other. Integrated modelling systems and frameworks are often the only way to take into account the important environmental processes and interactions, relevant spatial and temporal scales, and feedback mechanisms of complex systems for CEA. This book examines the ways in which interactions and relationships between environmental components are understood, paying special attention to climate, land, water quantity and quality, and both anthropogenic and natural stressors. It reviews modelling approaches for each component and reviews existing integrated modelling systems for CEA. Finally, it proposes an integrated modelling framework and provides perspectives on future research avenues for cumulative effects assessment

    Studies on Water Management Issues

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    This book shares knowledge gained through water management related research. It describes a broad range of approaches and technologies, of which have been developed and used by researchers for managing water resource problems. This multidisciplinary book covers water management issues under surface water management, groundwater management, water quality management, and water resource planning management subtopics. The main objective of this book is to enable a better understanding of these perspectives relating to water management practices. This book is expected to be useful to researchers, policy-makers, and non-governmental organizations working on water related projects in countries worldwide
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