Pub Date : 2023-11-15DOI: 10.1007/s10040-023-02745-z
Amandine L. Bosserelle, Leanne K. Morgan, David E. Dempsey, Irene Setiawan
Groundwater is present at shallow depth under many coastal low-lying cities. Despite the importance of protecting coastal urbanised areas from flooding and climate-change-induced sea-level rise, the effects of shallow groundwater fluctuations are rarely investigated. The aim of this study was to determine characteristics of shallow groundwater, including spatial and temporal trends in depths to groundwater and their relationship to natural and anthropogenic stressors. The study uses depth to groundwater measurements from a uniquely extensive and densely spaced monitoring network in Ōtautahi/Christchurch, New Zealand. Data-driven analysis approaches were applied, including spatial interpolation, autocorrelation, clustering, cross-correlation and trend analysis. These approaches are not commonly applied for groundwater assessments despite the potential for them to provide insights and information for city-wide systems. The comprehensive approach revealed discernible clusters and trends within the dataset. Responses to stresses such as rainfall events and stream flow were successfully classified using clustering analysis. The time series analysis indicated that in areas of shallow groundwater, low variation in levels occurred and this was also found using clustering. However, attributing some clusters to specific hydrogeological attributes or stressors posed challenges. The primary feature in hydrograph classification proved to be the proximity to tidal rivers and their correlation with tidal signals. These results highlight the value of using large datasets to characterise spatial and temporal variability of shallow groundwater in urban coastal settings and to assist with monitoring infrastructure planning in the face of future climate-change hazards.
{"title":"Shallow groundwater characterisation and hydrograph classification in the coastal city of Ōtautahi/Christchurch, New Zealand","authors":"Amandine L. Bosserelle, Leanne K. Morgan, David E. Dempsey, Irene Setiawan","doi":"10.1007/s10040-023-02745-z","DOIUrl":"https://doi.org/10.1007/s10040-023-02745-z","url":null,"abstract":"<p>Groundwater is present at shallow depth under many coastal low-lying cities. Despite the importance of protecting coastal urbanised areas from flooding and climate-change-induced sea-level rise, the effects of shallow groundwater fluctuations are rarely investigated. The aim of this study was to determine characteristics of shallow groundwater, including spatial and temporal trends in depths to groundwater and their relationship to natural and anthropogenic stressors. The study uses depth to groundwater measurements from a uniquely extensive and densely spaced monitoring network in Ōtautahi/Christchurch, New Zealand. Data-driven analysis approaches were applied, including spatial interpolation, autocorrelation, clustering, cross-correlation and trend analysis. These approaches are not commonly applied for groundwater assessments despite the potential for them to provide insights and information for city-wide systems. The comprehensive approach revealed discernible clusters and trends within the dataset. Responses to stresses such as rainfall events and stream flow were successfully classified using clustering analysis. The time series analysis indicated that in areas of shallow groundwater, low variation in levels occurred and this was also found using clustering. However, attributing some clusters to specific hydrogeological attributes or stressors posed challenges. The primary feature in hydrograph classification proved to be the proximity to tidal rivers and their correlation with tidal signals. These results highlight the value of using large datasets to characterise spatial and temporal variability of shallow groundwater in urban coastal settings and to assist with monitoring infrastructure planning in the face of future climate-change hazards.</p>","PeriodicalId":13013,"journal":{"name":"Hydrogeology Journal","volume":"15 2","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138525089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-15DOI: 10.1007/s10040-023-02746-y
Surabhi Upadhyay, Sangam Shrestha, Ho Huu Loc, S. Mohanasundaram, Santosh Dhungana, Sokneth Lim, Natthachet Tangdamrongsub
The Cambodia-Mekong River Delta Aquifer, a vital transboundary aquifer in the Lower Mekong Region of Southeast Asia, faces escalating challenges due to excessive groundwater extraction for agriculture and domestic purposes. In response, this study utilizes the Gravity Recovery and Climate Experiment (GRACE) satellite estimates, combined with land-surface-model and remote-sensing datasets to estimate groundwater storage anomalies (GWSA) across the aquifer where traditional monitoring is limited. The study further evaluates the consistency of GRACE-derived data in comparison to both localized in situ measurements and a global-scale hydrological model. Additionally, the spatio-temporal trends in groundwater depletion over a 14-year span (2003–2016) were mapped. The results reveal a good agreement between GRACE-derived GWSA, PC-Raster Global Water Balance (PCR-GLOBWB) model outputs, and observed in situ measurements, thereby underscoring the pivotal role of satellite observations in comprehensively assessing groundwater resources within the aquifer. The findings expose a concerning downward trend, with groundwater storage declining at a rate of ~0.68 cm/year, resulting in a total volume loss of 18.28 km3 over the 14-year span. Notably, the depletion rate is higher in the coastal regions of the Mekong Delta and certain areas within the Tonle Sap Basin. Discrepancies between GRACE and observed GWSA are attributed to multiple factors, including the absence of local signals, intricate hydrogeological dynamics, limitations in specific yield and storage estimations, and the uneven distribution of monitoring wells in the region. This research emphasizes the potential of GRACE estimates to supplement in situ observations on a regional scale, establishing a critical foundation for transboundary groundwater management strategies.
{"title":"Satellite-based estimates of declining groundwater storage in the transboundary Cambodia-Mekong River Delta Aquifer of the Lower Mekong region, Southeast Asia","authors":"Surabhi Upadhyay, Sangam Shrestha, Ho Huu Loc, S. Mohanasundaram, Santosh Dhungana, Sokneth Lim, Natthachet Tangdamrongsub","doi":"10.1007/s10040-023-02746-y","DOIUrl":"https://doi.org/10.1007/s10040-023-02746-y","url":null,"abstract":"<p>The Cambodia-Mekong River Delta Aquifer, a vital transboundary aquifer in the Lower Mekong Region of Southeast Asia, faces escalating challenges due to excessive groundwater extraction for agriculture and domestic purposes. In response, this study utilizes the Gravity Recovery and Climate Experiment (GRACE) satellite estimates, combined with land-surface-model and remote-sensing datasets to estimate groundwater storage anomalies (GWSA) across the aquifer where traditional monitoring is limited. The study further evaluates the consistency of GRACE-derived data in comparison to both localized in situ measurements and a global-scale hydrological model. Additionally, the spatio-temporal trends in groundwater depletion over a 14-year span (2003–2016) were mapped. The results reveal a good agreement between GRACE-derived GWSA, PC-Raster Global Water Balance (PCR-GLOBWB) model outputs, and observed in situ measurements, thereby underscoring the pivotal role of satellite observations in comprehensively assessing groundwater resources within the aquifer. The findings expose a concerning downward trend, with groundwater storage declining at a rate of ~0.68 cm/year, resulting in a total volume loss of 18.28 km<sup>3</sup> over the 14-year span. Notably, the depletion rate is higher in the coastal regions of the Mekong Delta and certain areas within the Tonle Sap Basin. Discrepancies between GRACE and observed GWSA are attributed to multiple factors, including the absence of local signals, intricate hydrogeological dynamics, limitations in specific yield and storage estimations, and the uneven distribution of monitoring wells in the region. This research emphasizes the potential of GRACE estimates to supplement in situ observations on a regional scale, establishing a critical foundation for transboundary groundwater management strategies.</p>","PeriodicalId":13013,"journal":{"name":"Hydrogeology Journal","volume":"9 3","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138525050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-14DOI: 10.1007/s10040-023-02747-x
Shoopala Uugulu, Heike Wanke, Paul Koeniger
Abstract Woody plants play a significant role in the global water cycle through water uptake by roots and evapotranspiration. A deuterium tracer was used to assess the active root depths for Salvia mellifera and Boscia albitrunca in the Ebenhaezer area (western Namibia). The tracer was inserted at different soil depths in December 2016. Xylem cores were obtained using an increment borer, and transpired water was collected using transpiration bags zipped around the plants’ leaves. Groundwater was collected from boreholes. Soil samples were collected after the rainy season using a hand auger. Xylem and soil water were extracted using a cryogenic vacuum extraction method and analysed for stable water isotopes. Only one S. mellifera transpiration sample showed a high deuterium content (516‰) where the tracer was inserted at 2.5-m soil depth. Elevated deuterium contents were observed in two S. mellifera xylem samples; tracer had been applied at 2.5 and 3 m depth (yielding 35 and 31‰ deuterium, respectively), which constitutes a possible active-root depth range for S. mellifera . At the end of the study period (May 2017), the average δ 18 O value for B. albitrunca xylem samples was similar to that of groundwater. The δ 18 O value for S. mellifera was between that of soil water and groundwater, indicating that this species uses groundwater and soil water available for groundwater recharge. Determination of the active root depth and source water for these species would help improve hydrological modelling by incorporating the influence of woody plants on groundwater recharge.
{"title":"Determinación del aporte de agua y de la profundidad de las raíces activas de plantas leñosas mediante un trazador de deuterio en un sitio de Savannah en el norte de la cuenca de Stampriet, Namibia","authors":"Shoopala Uugulu, Heike Wanke, Paul Koeniger","doi":"10.1007/s10040-023-02747-x","DOIUrl":"https://doi.org/10.1007/s10040-023-02747-x","url":null,"abstract":"Abstract Woody plants play a significant role in the global water cycle through water uptake by roots and evapotranspiration. A deuterium tracer was used to assess the active root depths for Salvia mellifera and Boscia albitrunca in the Ebenhaezer area (western Namibia). The tracer was inserted at different soil depths in December 2016. Xylem cores were obtained using an increment borer, and transpired water was collected using transpiration bags zipped around the plants’ leaves. Groundwater was collected from boreholes. Soil samples were collected after the rainy season using a hand auger. Xylem and soil water were extracted using a cryogenic vacuum extraction method and analysed for stable water isotopes. Only one S. mellifera transpiration sample showed a high deuterium content (516‰) where the tracer was inserted at 2.5-m soil depth. Elevated deuterium contents were observed in two S. mellifera xylem samples; tracer had been applied at 2.5 and 3 m depth (yielding 35 and 31‰ deuterium, respectively), which constitutes a possible active-root depth range for S. mellifera . At the end of the study period (May 2017), the average δ 18 O value for B. albitrunca xylem samples was similar to that of groundwater. The δ 18 O value for S. mellifera was between that of soil water and groundwater, indicating that this species uses groundwater and soil water available for groundwater recharge. Determination of the active root depth and source water for these species would help improve hydrological modelling by incorporating the influence of woody plants on groundwater recharge.","PeriodicalId":13013,"journal":{"name":"Hydrogeology Journal","volume":"82 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134901141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-10DOI: 10.1007/s10040-023-02744-0
K. Zouari, R. Trabelsi, Luis L. Araguás Araguás, S. Hussaini, S. Rabe, A. Alassane
{"title":"Utilización de trazadores hidroquímicos e isotópicos para investigar la calidad de las aguas subterráneas y los procesos de recarga del Sistema Acuífero Iullemeden en la región del Sahel (África Occidental)","authors":"K. Zouari, R. Trabelsi, Luis L. Araguás Araguás, S. Hussaini, S. Rabe, A. Alassane","doi":"10.1007/s10040-023-02744-0","DOIUrl":"https://doi.org/10.1007/s10040-023-02744-0","url":null,"abstract":"","PeriodicalId":13013,"journal":{"name":"Hydrogeology Journal","volume":"115 46","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135137798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-08DOI: 10.1007/s10040-023-02730-6
Tybaud Goyetche, Maria Pool, Jesus Carrera, Marc Diego-Feliu, Laura Martinez Perez, Albert Folch, Linda Luquot
{"title":"Using the tidal method to develop a conceptual model and for hydraulic characterization at the Argentona research site, NE Spain","authors":"Tybaud Goyetche, Maria Pool, Jesus Carrera, Marc Diego-Feliu, Laura Martinez Perez, Albert Folch, Linda Luquot","doi":"10.1007/s10040-023-02730-6","DOIUrl":"https://doi.org/10.1007/s10040-023-02730-6","url":null,"abstract":"","PeriodicalId":13013,"journal":{"name":"Hydrogeology Journal","volume":"65 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135390547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-08DOI: 10.1007/s10040-023-02733-3
Maria C. Caputo, Lorenzo De Carlo, Rita Masciale, Kim Perkins, Antonietta C. Turturro, John R. Nimmo
Abstract Preferential flow in the unsaturated zone strongly influences important hydrologic processes, such as infiltration, contaminant transport, and aquifer recharge. Because it entails various combinations of physical processes arising from the interactions of water, air, and solid particles in a porous medium, preferential flow is highly complex. Major research is needed to improve the ability to understand, quantify, model, and predict preferential flow. Toward a solution, a combination of diverse experimental measurements at multiple scales, from laboratory scale to mesoscale, has been implemented to detect and quantify preferential paths in carbonate and karstic unsaturated zones. This involves integration of information from (1) core samples, by means of mercury intrusion porosimeter, evaporation, quasi-steady centrifuge and dewpoint potentiometer laboratory methods, to investigate the effect of pore-size distribution on hydraulic characteristics and the potential activation of preferential flow, (2) field plot experiments with artificial sprinkling, to visualize preferential pathways related to secondary porosity, through use of geophysical measurements, and (3) mesoscale evaluation of field data through episodic master recession modeling of episodic recharge. This study demonstrates that preferential flow processes operate from core scale to two different field scales and impact on the qualitative and quantitative groundwater status, by entailing fast flow with subsequent effects on recharge rate and contaminant mobilizing. The presented results represent a rare example of preferential flow detection and numerical modeling by reducing underestimation of the recharge and contamination risks.
{"title":"通过多种实验方法利用人工降雨进行优先流的探测与定量化","authors":"Maria C. Caputo, Lorenzo De Carlo, Rita Masciale, Kim Perkins, Antonietta C. Turturro, John R. Nimmo","doi":"10.1007/s10040-023-02733-3","DOIUrl":"https://doi.org/10.1007/s10040-023-02733-3","url":null,"abstract":"Abstract Preferential flow in the unsaturated zone strongly influences important hydrologic processes, such as infiltration, contaminant transport, and aquifer recharge. Because it entails various combinations of physical processes arising from the interactions of water, air, and solid particles in a porous medium, preferential flow is highly complex. Major research is needed to improve the ability to understand, quantify, model, and predict preferential flow. Toward a solution, a combination of diverse experimental measurements at multiple scales, from laboratory scale to mesoscale, has been implemented to detect and quantify preferential paths in carbonate and karstic unsaturated zones. This involves integration of information from (1) core samples, by means of mercury intrusion porosimeter, evaporation, quasi-steady centrifuge and dewpoint potentiometer laboratory methods, to investigate the effect of pore-size distribution on hydraulic characteristics and the potential activation of preferential flow, (2) field plot experiments with artificial sprinkling, to visualize preferential pathways related to secondary porosity, through use of geophysical measurements, and (3) mesoscale evaluation of field data through episodic master recession modeling of episodic recharge. This study demonstrates that preferential flow processes operate from core scale to two different field scales and impact on the qualitative and quantitative groundwater status, by entailing fast flow with subsequent effects on recharge rate and contaminant mobilizing. The presented results represent a rare example of preferential flow detection and numerical modeling by reducing underestimation of the recharge and contamination risks.","PeriodicalId":13013,"journal":{"name":"Hydrogeology Journal","volume":"86 11","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135390085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-02DOI: 10.1007/s10040-023-02737-z
Ryma Aissat, Alexandre Pryet, Marc Saltel, Alain Dupuy
Abstract The parameterization of spatially distributed hydraulic properties is one of the most crucial steps in groundwater modeling. A common approach is to estimate hydraulic properties at a set of pilot points and interpolate the values at each model cell. Despite the popularity of this method, several questions remain about the optimum number and distribution of pilot points, which are determining factors for the efficiency of the method. This study proposes a strategy for optimal pilot point parameterization that minimizes the number of parameters while maximizing the assimilation of an observed dataset unevenly distributed in space. The performance of different pilot point distributions has been compared with a synthetic groundwater model, considering regular grids of pilot points with different spacings and adaptive grids with different refinement criteria. This work considered both prior and iterative refinements, with a parameter estimation step between successive refinements. The parameter estimation was conducted with the Gauss–Levenberg–Marquardt algorithm, and the strategies were ranked according to the number of model calls to reach the target objective function. The strategy leading to the best fit with the measurement dataset at the minimum computational burden is an adaptive grid of pilot points with prior refinement based on measurement density. This strategy was successfully implemented on a regional, multilayered groundwater flow model in the south-western geological basin of France.
{"title":"Comparison of different pilot point parameterization strategies when measurements are unevenly distributed in space","authors":"Ryma Aissat, Alexandre Pryet, Marc Saltel, Alain Dupuy","doi":"10.1007/s10040-023-02737-z","DOIUrl":"https://doi.org/10.1007/s10040-023-02737-z","url":null,"abstract":"Abstract The parameterization of spatially distributed hydraulic properties is one of the most crucial steps in groundwater modeling. A common approach is to estimate hydraulic properties at a set of pilot points and interpolate the values at each model cell. Despite the popularity of this method, several questions remain about the optimum number and distribution of pilot points, which are determining factors for the efficiency of the method. This study proposes a strategy for optimal pilot point parameterization that minimizes the number of parameters while maximizing the assimilation of an observed dataset unevenly distributed in space. The performance of different pilot point distributions has been compared with a synthetic groundwater model, considering regular grids of pilot points with different spacings and adaptive grids with different refinement criteria. This work considered both prior and iterative refinements, with a parameter estimation step between successive refinements. The parameter estimation was conducted with the Gauss–Levenberg–Marquardt algorithm, and the strategies were ranked according to the number of model calls to reach the target objective function. The strategy leading to the best fit with the measurement dataset at the minimum computational burden is an adaptive grid of pilot points with prior refinement based on measurement density. This strategy was successfully implemented on a regional, multilayered groundwater flow model in the south-western geological basin of France.","PeriodicalId":13013,"journal":{"name":"Hydrogeology Journal","volume":"35 10","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135934293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1007/s10040-023-02743-1
Jacob Kidmose, Bertel Nilsson, Niels Korsholm Klem, Philip Grinder Pedersen, Hans Jørgen Henriksen, Torben O. Sonnenborg
Abstract Protection of fractured carbonate aquifers is often based on a single-porosity description of a dual-porosity system. However, it is difficult to assess a trustworthy value of the effective porosity based on scientific principles; thus, a range of estimates is often suggested. The complexity of the problem is compounded by the fact that the effective porosity may be scale-dependent. This paper investigates whether it is possible to describe solute transport in fractured carbonate rocks with an equivalent porous medium model using a constant value of effective porosity. It is assumed that the dual-porosity model provides an acceptable description of transport mechanisms in fractured porous rock and that it is possible to estimate the parameters needed in the single-porosity models from results generated by the dual-porosity model. The effective porosity is estimated from the dual-porosity results that are used as targets. For Danish chalk, an effective porosity of 13% (11–17%) is estimated. However, it is demonstrated that the estimated effective porosity is only valid at the specific transport time (1 year) from which simulation results of the dual-porosity model were extracted. The effective porosity is shown to increase with travel time until equilibrium conditions are realised between the fractures and matrix, following which, the effective porosity equals the matrix porosity and will maintain this value at larger transport times. Assuming that the dual-porosity model provides a trustworthy description of solute transport in fractured chalk and limestone, a method to estimate the effective porosity of an equivalent porous medium model is presented.
{"title":"Kan effektiv porøsitet bruges til at estimere boringsnære beskyttelseszoner i opsprækket kalk?","authors":"Jacob Kidmose, Bertel Nilsson, Niels Korsholm Klem, Philip Grinder Pedersen, Hans Jørgen Henriksen, Torben O. Sonnenborg","doi":"10.1007/s10040-023-02743-1","DOIUrl":"https://doi.org/10.1007/s10040-023-02743-1","url":null,"abstract":"Abstract Protection of fractured carbonate aquifers is often based on a single-porosity description of a dual-porosity system. However, it is difficult to assess a trustworthy value of the effective porosity based on scientific principles; thus, a range of estimates is often suggested. The complexity of the problem is compounded by the fact that the effective porosity may be scale-dependent. This paper investigates whether it is possible to describe solute transport in fractured carbonate rocks with an equivalent porous medium model using a constant value of effective porosity. It is assumed that the dual-porosity model provides an acceptable description of transport mechanisms in fractured porous rock and that it is possible to estimate the parameters needed in the single-porosity models from results generated by the dual-porosity model. The effective porosity is estimated from the dual-porosity results that are used as targets. For Danish chalk, an effective porosity of 13% (11–17%) is estimated. However, it is demonstrated that the estimated effective porosity is only valid at the specific transport time (1 year) from which simulation results of the dual-porosity model were extracted. The effective porosity is shown to increase with travel time until equilibrium conditions are realised between the fractures and matrix, following which, the effective porosity equals the matrix porosity and will maintain this value at larger transport times. Assuming that the dual-porosity model provides a trustworthy description of solute transport in fractured chalk and limestone, a method to estimate the effective porosity of an equivalent porous medium model is presented.","PeriodicalId":13013,"journal":{"name":"Hydrogeology Journal","volume":"282 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135273474","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-31DOI: 10.1007/s10040-023-02728-0
Romain Deleu, Amaël Poulain, Gaëtan Rochez, Sandra Soares-Frazao, Guy Van Rentergem, Eli De Poorter, Vincent Hallet
Abstract In karstic environments, it is not unusual for an underground river to split into two or more streams (diffluence) and merge back together downstream (confluence). This kind of behavior can generate multipeaked breakthrough curves (BTCs) in dye tracing at a sampling site located downstream of the confluence(s). It is also possible that such a phenomenon is difficult to highlight with dye tracing if the tracer clouds coming from the different streams reach the sampling locations at the same time. In this study, an attempt at quantifying the importance of different criteria in the occurrence of a multipeaked BTC is done by performing a dye tracing campaign in a two-tributaries diffluence-confluence (DC) system and using a one-dimensional solute transport model. The results from both field data and the solute transport model suggest that a double-peaked BTC occurs downstream of a DC system if the following conditions are met: (1) the injection is done close enough to the diffluence, (2) the sampling point is located not too far from the confluence, and (3) the two (or more) streams have sufficiently contrasted travel times from the diffluence to the confluence. The paper illustrates that, even if a diffluence occurs in a karstic river, multipeaked BTCs are not necessarily observed downstream of the confluence if these three conditions are not met. Therefore, characterizing a DC system using dye tracing is a real challenge. This could explain why publications that report studies involving multipeaked BTCs are quite rare.
{"title":"Curvas de flujo con múltiples picos en ríos kársticos: efectos de un sistema de difluencia-confluencia","authors":"Romain Deleu, Amaël Poulain, Gaëtan Rochez, Sandra Soares-Frazao, Guy Van Rentergem, Eli De Poorter, Vincent Hallet","doi":"10.1007/s10040-023-02728-0","DOIUrl":"https://doi.org/10.1007/s10040-023-02728-0","url":null,"abstract":"Abstract In karstic environments, it is not unusual for an underground river to split into two or more streams (diffluence) and merge back together downstream (confluence). This kind of behavior can generate multipeaked breakthrough curves (BTCs) in dye tracing at a sampling site located downstream of the confluence(s). It is also possible that such a phenomenon is difficult to highlight with dye tracing if the tracer clouds coming from the different streams reach the sampling locations at the same time. In this study, an attempt at quantifying the importance of different criteria in the occurrence of a multipeaked BTC is done by performing a dye tracing campaign in a two-tributaries diffluence-confluence (DC) system and using a one-dimensional solute transport model. The results from both field data and the solute transport model suggest that a double-peaked BTC occurs downstream of a DC system if the following conditions are met: (1) the injection is done close enough to the diffluence, (2) the sampling point is located not too far from the confluence, and (3) the two (or more) streams have sufficiently contrasted travel times from the diffluence to the confluence. The paper illustrates that, even if a diffluence occurs in a karstic river, multipeaked BTCs are not necessarily observed downstream of the confluence if these three conditions are not met. Therefore, characterizing a DC system using dye tracing is a real challenge. This could explain why publications that report studies involving multipeaked BTCs are quite rare.","PeriodicalId":13013,"journal":{"name":"Hydrogeology Journal","volume":"2023 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135872520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-31DOI: 10.1007/s10040-023-02723-5
Rebecca Doble, Glen Walker, Russell Crosbie, Joseph Guillaume, Tanya Doody
Abstract The Murray-Darling Basin (MDB) is a highly allocated and regulated, mostly semiarid basin in south-eastern Australia, where groundwater is a significant water resource. Future climate predictions for the MDB include an expansion of arid and semiarid climate zones to replace temperate areas. The impacts of climate change are already evident in declining groundwater levels and changes in the connection status between rivers and groundwater, and modelling has predicted a further reduction in future groundwater recharge and ongoing declines in groundwater levels. This is predicted to further reduce river baseflow and negatively impact groundwater-dependent ecosystems (GDEs), and these system responses to a changing climate and extreme events are complex and not always well understood. This report provides an overview of the current state of knowledge of groundwater response to a changing climate for the MDB, and outlines challenges and opportunities for future groundwater research and management. Opportunities for the region include improving data systems and acquisition through automation and novel data sources, and growing capability in integrated, risk-based modelling. Quantification of the groundwater/surface-water connection response to declining groundwater levels, and assessing GDE water requirements and thresholds, would enable identification of vulnerable systems and inform the development of metrics for adaptive management, improving the ability to respond to climate extremes. There is potential to adapt policy to support active management of groundwater where required, including conjunctive use and water banking. Improving knowledge sharing and water literacy, including understanding community values of groundwater and GDEs, would support future decision-making.
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