Rasoul Mirghafari, Ehsan Nikooee, Amir Raoof, Ghassem Habibagahi
Understanding specific air–water interfacial area (SAWIA) is essential for characterizing and modeling various phenomena in vadose zone hydrology, such as virus and colloid transport, contaminant dissolution, evaporation, and the hydro‐mechanical behavior of unsaturated soils. Traditional measurement methods, including X‐ray imaging and tracer techniques, often encounter challenges, leading to a scarcity of studies that provide a reliable relationship for SAWIA. Currently, no pedotransfer function in the literature links SAWIA with saturation and suction using readily measurable soil properties such as median grain size and porosity. In this study, we initially developed a pore network model capable of predicting SAWIA by calibrating it with corresponding soil‐water retention curves (SWRCs). We then used these models to compile a comprehensive database of SAWIA for six sandy soils, for which experimental SWRCs were available, covering a range of median grain sizes and porosities. Utilizing this database, we established a pedotransfer function through multigene genetic programming. The accuracy of this function was validated against experimental data not previously used in its training and testing. Our parametric study indicated that increases in either porosity or median particle size led to a decrease in the regions exhibiting higher SAWIA in terms of saturation and suction.
{"title":"Determination of a pedotransfer function for specific air–water interfacial area in sandy soils: A pore network‐informed multigene genetic programming approach","authors":"Rasoul Mirghafari, Ehsan Nikooee, Amir Raoof, Ghassem Habibagahi","doi":"10.1002/vzj2.20352","DOIUrl":"https://doi.org/10.1002/vzj2.20352","url":null,"abstract":"Understanding specific air–water interfacial area (SAWIA) is essential for characterizing and modeling various phenomena in vadose zone hydrology, such as virus and colloid transport, contaminant dissolution, evaporation, and the hydro‐mechanical behavior of unsaturated soils. Traditional measurement methods, including X‐ray imaging and tracer techniques, often encounter challenges, leading to a scarcity of studies that provide a reliable relationship for SAWIA. Currently, no pedotransfer function in the literature links SAWIA with saturation and suction using readily measurable soil properties such as median grain size and porosity. In this study, we initially developed a pore network model capable of predicting SAWIA by calibrating it with corresponding soil‐water retention curves (SWRCs). We then used these models to compile a comprehensive database of SAWIA for six sandy soils, for which experimental SWRCs were available, covering a range of median grain sizes and porosities. Utilizing this database, we established a pedotransfer function through multigene genetic programming. The accuracy of this function was validated against experimental data not previously used in its training and testing. Our parametric study indicated that increases in either porosity or median particle size led to a decrease in the regions exhibiting higher SAWIA in terms of saturation and suction.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141191691","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}
William Godoy, Elizabeth M. Pontedeiro, Rafael A. B. R. Barros, Enno T. de Vries, Amir Raoof, Martinus Th. van Genuchten, Paulo Couto
Accurately estimating the petrophysical properties of heterogeneous carbonate rocks across various scales poses significant challenges, particularly within the context of water and hydrocarbon reservoir studies. Digital rock analysis techniques, such as X‐ray computed microtomography and synchrotron‐light‐based imaging, are increasingly employed to study the complex pore structure of carbonate rocks. However, several technical limitations remain, notably the need to balance the volume of interest with the maximum achievable resolution, which is influenced by geometric properties of the source–detector distance in each apparatus. Typically, higher resolutions necessitate smaller sample volumes, leading to a portion of the pore structure (the sub‐resolution or unresolved porosity), that remain undetected. In this study, X‐ray microtomography is used to infer the fluid flow properties of a carbonate rock sample having a substantial fraction of porosity below the imaging resolution. The existence of unresolved porosity is verified by comparisons with nuclear magnetic resonance (NMR) data. We introduce a methodology for modeling the sub‐resolution pore structure within images by accounting for unresolved pore bodies and pore throats derived from a predetermined distribution of pore throat radii. The process identifies preferential pathways between visible pores using the shortest distance and establishes connections between these pores by allocating pore bodies and throats along these paths, while ensuring compatibility with the NMR measurements. Single‐phase flow simulations are conducted on the full volume of a selected heterogeneous rock sample by using the developed pore network model. Results are then compared with petrophysical data obtained from laboratory measurements.
准确估算不同尺度异质碳酸盐岩的岩石物理特性是一项重大挑战，尤其是在水和碳氢化合物储层研究方面。在研究碳酸盐岩复杂的孔隙结构时，人们越来越多地采用数字岩石分析技术，如 X 射线计算机显微层析技术和同步辐射成像技术。然而，仍然存在一些技术限制，特别是需要在感兴趣的体积与可实现的最大分辨率之间取得平衡，而这受到每台仪器的源-探测器距离的几何特性的影响。通常情况下，分辨率越高，样品体积就越小，从而导致部分孔隙结构（次分辨率或未解决的孔隙度）仍未被探测到。在本研究中，X 射线显微层析成像技术被用于推断碳酸盐岩样本的流体流动特性，该样本中的大部分孔隙度低于成像分辨率。通过与核磁共振（NMR）数据进行比较，验证了未解决孔隙度的存在。我们介绍了一种方法，通过考虑未解决的孔体和孔喉半径预定分布得出的孔喉，对图像中的亚分辨率孔隙结构进行建模。该过程使用最短距离识别可见孔隙之间的优先路径，并通过沿这些路径分配孔体和孔喉建立这些孔隙之间的连接，同时确保与核磁共振测量的兼容性。利用所开发的孔隙网络模型，对所选异质岩石样本的整个体积进行单相流模拟。然后将结果与实验室测量获得的岩石物理数据进行比较。
{"title":"Modeling sub‐resolution porosity of a heterogeneous carbonate rock sample","authors":"William Godoy, Elizabeth M. Pontedeiro, Rafael A. B. R. Barros, Enno T. de Vries, Amir Raoof, Martinus Th. van Genuchten, Paulo Couto","doi":"10.1002/vzj2.20348","DOIUrl":"https://doi.org/10.1002/vzj2.20348","url":null,"abstract":"Accurately estimating the petrophysical properties of heterogeneous carbonate rocks across various scales poses significant challenges, particularly within the context of water and hydrocarbon reservoir studies. Digital rock analysis techniques, such as X‐ray computed microtomography and synchrotron‐light‐based imaging, are increasingly employed to study the complex pore structure of carbonate rocks. However, several technical limitations remain, notably the need to balance the volume of interest with the maximum achievable resolution, which is influenced by geometric properties of the source–detector distance in each apparatus. Typically, higher resolutions necessitate smaller sample volumes, leading to a portion of the pore structure (the sub‐resolution or unresolved porosity), that remain undetected. In this study, X‐ray microtomography is used to infer the fluid flow properties of a carbonate rock sample having a substantial fraction of porosity below the imaging resolution. The existence of unresolved porosity is verified by comparisons with nuclear magnetic resonance (NMR) data. We introduce a methodology for modeling the sub‐resolution pore structure within images by accounting for unresolved pore bodies and pore throats derived from a predetermined distribution of pore throat radii. The process identifies preferential pathways between visible pores using the shortest distance and establishes connections between these pores by allocating pore bodies and throats along these paths, while ensuring compatibility with the NMR measurements. Single‐phase flow simulations are conducted on the full volume of a selected heterogeneous rock sample by using the developed pore network model. Results are then compared with petrophysical data obtained from laboratory measurements.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141191710","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}
Beaulah Pragg, T. K. K. Chamindu Deepagoda, Keith Cameron, Hong Di, Timothy J. Clough, Sam Carrick
Global food production relying on irrigated agriculture accounts for >70% of the global freshwater withdrawal. A thorough understanding of soil–water characteristics (SWCs) and critical soil–water values in the soil and subsoil is important for effective management of irrigated water. A critical soil–water “window” for plants is generally taken as the plant‐available water window without considering diffusion‐dominated soil aeration as a co‐requisite. This study examined SWC curves in vadose soil profiles (up to 1.5‐m depth) in eight pasture soils. The soil moisture measurements were made over matric potentials ranging from −1 to −1500 kPa using tension table and pressure plate apparatus. The van Genuchten model was used to parameterize the measured SWC curve, while the Millington‐Quirk model was used to derive soil–gas diffusivity from measured soil physical properties. We defined critical soil–water windows considering the threshold values for both plant‐available water and soil–gas diffusivity to ensure water and aeration corequisites for plant growth. The results clearly distinguished depth‐dependent regimes of gravitational, plant‐available, and unavailable water in selected profiles and their responses to soil structural changes across the depth. In some of the observed soil profiles, only 30%–60% of the plant‐available water window was able to be utilized by plants because the remainder existed under soil conditions where soil aeration was inadequate for plant growth, emphasizing the importance of considering both the plant's water and aeration requirements during irrigation scheduling. Further, the infiltration profiles in two selected soils under simulated irrigation highlighted the importance of a priori knowledge of the soil structure in deeper soil layers for scheduling irrigation.
{"title":"Irrigation scheduling needs to consider both plant‐available water and soil aeration requirements","authors":"Beaulah Pragg, T. K. K. Chamindu Deepagoda, Keith Cameron, Hong Di, Timothy J. Clough, Sam Carrick","doi":"10.1002/vzj2.20344","DOIUrl":"https://doi.org/10.1002/vzj2.20344","url":null,"abstract":"Global food production relying on irrigated agriculture accounts for >70% of the global freshwater withdrawal. A thorough understanding of soil–water characteristics (SWCs) and critical soil–water values in the soil and subsoil is important for effective management of irrigated water. A critical soil–water “window” for plants is generally taken as the plant‐available water window without considering diffusion‐dominated soil aeration as a co‐requisite. This study examined SWC curves in vadose soil profiles (up to 1.5‐m depth) in eight pasture soils. The soil moisture measurements were made over matric potentials ranging from −1 to −1500 kPa using tension table and pressure plate apparatus. The van Genuchten model was used to parameterize the measured SWC curve, while the Millington‐Quirk model was used to derive soil–gas diffusivity from measured soil physical properties. We defined critical soil–water windows considering the threshold values for both plant‐available water and soil–gas diffusivity to ensure water and aeration corequisites for plant growth. The results clearly distinguished depth‐dependent regimes of gravitational, plant‐available, and unavailable water in selected profiles and their responses to soil structural changes across the depth. In some of the observed soil profiles, only 30%–60% of the plant‐available water window was able to be utilized by plants because the remainder existed under soil conditions where soil aeration was inadequate for plant growth, emphasizing the importance of considering both the plant's water and aeration requirements during irrigation scheduling. Further, the infiltration profiles in two selected soils under simulated irrigation highlighted the importance of a priori knowledge of the soil structure in deeper soil layers for scheduling irrigation.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141191767","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}
Victoria A. Walker, Michael H. Cosh, Tyson E. Ochsner
Long‐term in situ soil moisture monitoring inevitably requires sensors to be replaced. Ensuing discontinuities in the data record can be mitigated by intercalibration, however it is unclear how long the existing sensor needs to remain alongside the newly installed before there is enough overlapping data to generate a robust intercalibration. We used 154 pairs of established and newly installed sensors within the Marena, Oklahoma, In Situ Sensor Testbed to determine if there is a minimum overlap time that should be considered when planning upcoming replacements. Hourly observations of the existing sensor were linearly calibrated to those of the newly installed sensor with coefficients determined from overlap periods incremented by 30 days until a reference period of 2 years was reached. The resulting bias, root‐mean‐square error, and correlation coefficient for sensor pairs indicate that a minimum of 6 to 9 months of overlapping data are required to generate a successful intercalibration. Extending that to a full year before decommissioning the old sensor results in a stable intercalibration with higher confidence.
{"title":"Calculating a minimum overlap period for successful intercalibration of soil moisture sensors","authors":"Victoria A. Walker, Michael H. Cosh, Tyson E. Ochsner","doi":"10.1002/vzj2.20346","DOIUrl":"https://doi.org/10.1002/vzj2.20346","url":null,"abstract":"Long‐term in situ soil moisture monitoring inevitably requires sensors to be replaced. Ensuing discontinuities in the data record can be mitigated by intercalibration, however it is unclear how long the existing sensor needs to remain alongside the newly installed before there is enough overlapping data to generate a robust intercalibration. We used 154 pairs of established and newly installed sensors within the Marena, Oklahoma, In Situ Sensor Testbed to determine if there is a minimum overlap time that should be considered when planning upcoming replacements. Hourly observations of the existing sensor were linearly calibrated to those of the newly installed sensor with coefficients determined from overlap periods incremented by 30 days until a reference period of 2 years was reached. The resulting bias, root‐mean‐square error, and correlation coefficient for sensor pairs indicate that a minimum of 6 to 9 months of overlapping data are required to generate a successful intercalibration. Extending that to a full year before decommissioning the old sensor results in a stable intercalibration with higher confidence.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141191664","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}
Alireza Daman Shokouh, Ehsan Nikooee, Ghassem Habibagahi, S. Majid Hassanizadeh
Modeling two‐phase flow in unsaturated porous media is not only important to vadose zone hydrology but also of great value in diverse disciplines. Common approaches use a simplified relationship between fluid pressure difference and saturation, neglecting the influence of saturation change rates. However, many studies have suggested that the applicability of this approach is limited to situations where the rate of change in saturation is insignificant. Despite several studies highlighting the importance of non‐equilibrium capillarity effects in unsaturated flow modeling, its significance in the mechanical response of the porous medium remains unclear. This study thus aims to address this gap by comparing the simulation results of the traditional static approach and an advanced approach that incorporates dynamic capillarity effects. The comparison is conducted under various flow boundary conditions to assess the magnitude of the differences between the two approaches. The results indicate that as the hydraulic boundary conditions’ absolute values increase, the contrast between the mechanical response of the two simulation scenarios (dynamic and static) becomes more significant. For instance, the dynamic model can predict shear strengths up to 50% higher than the static model. This highlights the importance of considering non‐equilibrium effects while modeling the mechanical behavior of an unsaturated porous medium. Finally, the parametric study of the effect of dynamic coefficient, air entry value, and saturated conductivity reveals the more pronounced effect of the dynamic coefficient on the mechanical response.
{"title":"Effects of dynamic capillarity on the shear strength of sandy soils during transient two‐phase flow: Insights from non‐equilibrium triaxial simulations","authors":"Alireza Daman Shokouh, Ehsan Nikooee, Ghassem Habibagahi, S. Majid Hassanizadeh","doi":"10.1002/vzj2.20351","DOIUrl":"https://doi.org/10.1002/vzj2.20351","url":null,"abstract":"Modeling two‐phase flow in unsaturated porous media is not only important to vadose zone hydrology but also of great value in diverse disciplines. Common approaches use a simplified relationship between fluid pressure difference and saturation, neglecting the influence of saturation change rates. However, many studies have suggested that the applicability of this approach is limited to situations where the rate of change in saturation is insignificant. Despite several studies highlighting the importance of non‐equilibrium capillarity effects in unsaturated flow modeling, its significance in the mechanical response of the porous medium remains unclear. This study thus aims to address this gap by comparing the simulation results of the traditional static approach and an advanced approach that incorporates dynamic capillarity effects. The comparison is conducted under various flow boundary conditions to assess the magnitude of the differences between the two approaches. The results indicate that as the hydraulic boundary conditions’ absolute values increase, the contrast between the mechanical response of the two simulation scenarios (dynamic and static) becomes more significant. For instance, the dynamic model can predict shear strengths up to 50% higher than the static model. This highlights the importance of considering non‐equilibrium effects while modeling the mechanical behavior of an unsaturated porous medium. Finally, the parametric study of the effect of dynamic coefficient, air entry value, and saturated conductivity reveals the more pronounced effect of the dynamic coefficient on the mechanical response.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141191662","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}
The Peters–Durner–Iden (PDI) model system for describing soil hydraulic properties (SHP) has been developed over a decade. Inspired by Rien van Genuchten's seminal work, the PDI system focuses on an efficient and simple parameterization of water retention curves and hydraulic conductivity curves (HCC) across the entire soil moisture spectrum. By combining capillary and non‐capillary components for water retention and conductivity, it aims to reconcile mathematical simplicity and insights on water adsorption and film flow in soils. Recent developments have reduced the number of free parameters of the conductivity model to zero, enhancing the model's applicability in cases of limited data availability. The first reduction was achieved by a prediction of absolute non‐capillary conductivity based on the consideration of film and corner flow on the pore scale, and the second by a prediction of absolute capillary conductivity by a capillary bundle model. This allows a complete characterization of SHP over the entire moisture range with only four retention curve parameters. The inclusion of a maximum pore size in the capillary conductivity model prevents an unrealistic drop of the HCC near saturation. This paper provides a comprehensive overview of the PDI model system, emphasizing its conceptual features and mathematical details. An Excel sheet and a Python code stored in a repository are provided for accessibility.
{"title":"The PDI model system for parameterizing soil hydraulic properties","authors":"Andre Peters, Wolfgang Durner, Sascha Iden","doi":"10.1002/vzj2.20338","DOIUrl":"https://doi.org/10.1002/vzj2.20338","url":null,"abstract":"The Peters–Durner–Iden (PDI) model system for describing soil hydraulic properties (SHP) has been developed over a decade. Inspired by Rien van Genuchten's seminal work, the PDI system focuses on an efficient and simple parameterization of water retention curves and hydraulic conductivity curves (HCC) across the entire soil moisture spectrum. By combining capillary and non‐capillary components for water retention and conductivity, it aims to reconcile mathematical simplicity and insights on water adsorption and film flow in soils. Recent developments have reduced the number of free parameters of the conductivity model to zero, enhancing the model's applicability in cases of limited data availability. The first reduction was achieved by a prediction of absolute non‐capillary conductivity based on the consideration of film and corner flow on the pore scale, and the second by a prediction of absolute capillary conductivity by a capillary bundle model. This allows a complete characterization of SHP over the entire moisture range with only four retention curve parameters. The inclusion of a maximum pore size in the capillary conductivity model prevents an unrealistic drop of the HCC near saturation. This paper provides a comprehensive overview of the PDI model system, emphasizing its conceptual features and mathematical details. An Excel sheet and a Python code stored in a repository are provided for accessibility.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140931051","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}
Evaporation of soil water depends not only on climatic conditions, soil surface roughness, soil texture, and soil hydraulic properties but also on the soils’ macrostructure. Evaporation is characterized by water losses over time for a defined soil volume, where soils are assumed to be homogeneous in texture and structure. In this technical note, we investigated the potential and limitations of 3D modeling of evaporation processes on 250 cm3 soil cores with structural features ≥480 µm determined by X‐ray computed tomography. For this, we used isothermal Richards equation as the main governing equation, accounting also for isothermal vapor flow. We simulated two evaporation experiments with same soil texture but contrasting macrostructures, that is, the spatial arrangement of voxels classified as soil matrix and air‐filled voids, of a ploughed and non‐ploughed grassland soil with HYDRUS 3D. In both simulations, we fixed the potential evaporation rates to the experimental rates and evaluated simulation results with measured matric potential data at two depths (1.25 cm and 3.75 cm) continuously recorded at 10 min intervals. We could show that the simulations of bare soil evaporation were able to predict the tensiometer dynamics and water losses for the full experimental time of 7 days. The simulation provided unique spatial information of water content and flow velocities as a function of time, which are important when studying the effect of air‐filled macropores, macro‐connectivity of soil matrix, and water dynamics on soil evaporation.
土壤水的蒸发不仅取决于气候条件、土壤表面粗糙度、土壤质地和土壤水力特性，还取决于土壤的宏观结构。蒸发的特点是，在假定土壤质地和结构均质的情况下，确定的土壤体积中的水分随时间的变化而损失。在本技术说明中，我们研究了通过 X 射线计算机断层扫描确定结构特征 ≥480 µm 的 250 cm3 土芯蒸发过程三维建模的潜力和局限性。为此，我们使用等温理查兹方程作为主要控制方程，同时考虑等温蒸汽流。我们使用 HYDRUS 3D 模拟了两个蒸发实验，它们的土壤质地相同，但宏观结构（即分为土壤基质和充满空气的空隙的体素的空间排列）却截然不同，分别是耕地和非耕地草原土壤。在这两种模拟中，我们都将潜在蒸发率固定为实验蒸发率，并以 10 分钟间隔连续记录的两个深度（1.25 厘米和 3.75 厘米）的测量母势数据来评估模拟结果。结果表明，裸露土壤蒸发模拟能够预测张力计的动态和整个 7 天实验时间内的水分损失。模拟提供了含水量和流速随时间变化的独特空间信息，这对于研究充满空气的大孔隙、土壤基质的宏观连通性和水动力学对土壤蒸发的影响非常重要。
{"title":"Simulating bare soil evaporation for undisturbed soil cores—Using HYDRUS 3D simulation on X‐ray µCT determined soil macrostructures","authors":"Frederic Leuther, Efstathios Diamantopoulos","doi":"10.1002/vzj2.20339","DOIUrl":"https://doi.org/10.1002/vzj2.20339","url":null,"abstract":"Evaporation of soil water depends not only on climatic conditions, soil surface roughness, soil texture, and soil hydraulic properties but also on the soils’ macrostructure. Evaporation is characterized by water losses over time for a defined soil volume, where soils are assumed to be homogeneous in texture and structure. In this technical note, we investigated the potential and limitations of 3D modeling of evaporation processes on 250 cm<jats:sup>3</jats:sup> soil cores with structural features ≥480 µm determined by X‐ray computed tomography. For this, we used isothermal Richards equation as the main governing equation, accounting also for isothermal vapor flow. We simulated two evaporation experiments with same soil texture but contrasting macrostructures, that is, the spatial arrangement of voxels classified as soil matrix and air‐filled voids, of a ploughed and non‐ploughed grassland soil with HYDRUS 3D. In both simulations, we fixed the potential evaporation rates to the experimental rates and evaluated simulation results with measured matric potential data at two depths (1.25 cm and 3.75 cm) continuously recorded at 10 min intervals. We could show that the simulations of bare soil evaporation were able to predict the tensiometer dynamics and water losses for the full experimental time of 7 days. The simulation provided unique spatial information of water content and flow velocities as a function of time, which are important when studying the effect of air‐filled macropores, macro‐connectivity of soil matrix, and water dynamics on soil evaporation.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140930969","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}
S. H. Sadeghi, H. W. Loescher, P. W. Jacoby, P. L. Sullivan
Finding an explicit solution to the widely used Green–Ampt (G–A) one‐dimensional infiltration model has been subject of efforts for more than half a century. We derived an explicit semiempirical approach that combines accuracy with simplicity, a concept that has been generally neglected in previous studies. The equation is , with F (L), Ks (L/T), S (L/T0.5) and t (T) being cumulative infiltration, saturated hydraulic conductivity, sorptivity, and time, respectively. Relative errors (ɛ) by the application of this equation generally do not exceed ±0.3% in most applied infiltration problems faced by water resources engineering today. We show both numerically and mathematically that │ɛ│> 0.3% could only occur if Kst/F > 0.904, a criterion that could apply to sand and loamy sand soils (i.e., coarse texture) and if they experience infiltration rates for over 6 h and 19 h, respectively. Hence, we also derived a simple linear adjustment in the model as Fadj ≅ 0.9796 F + 0.335 S2/Ks to address these longer infiltration rates, and to assure that ɛ remains within the expected ±0.3% range of uncertainty. A linearized regression technique was also developed to accurately estimate S and Ks when the G–A model is used. We numerically demonstrated that our fitting method could be used even when the G–A approach is less valid (diffusive soils), provided that the actual value of the capillary length (λ) is initially known. An added benefit of our approach is that by setting λ equal to 1/3 and 2/3, it can significantly limit the range of initializing, unknown, a priori values of S and Ks, as these two parameters are estimated through the inverse solution of implicit infiltration models. Due to the model's simplicity and accuracy, our solution should find application among hydrologists, natural resource scientists, and engineers who wish to easily derive accurate estimations from the G–A infiltration approach and/or estimate sorptivity and hydraulic conductivity without encountering divergence problems.
{"title":"A simple, accurate, and explicit form of the Green–Ampt model to estimate infiltration, sorptivity, and hydraulic conductivity","authors":"S. H. Sadeghi, H. W. Loescher, P. W. Jacoby, P. L. Sullivan","doi":"10.1002/vzj2.20341","DOIUrl":"https://doi.org/10.1002/vzj2.20341","url":null,"abstract":"Finding an explicit solution to the widely used Green–Ampt (G–A) one‐dimensional infiltration model has been subject of efforts for more than half a century. We derived an explicit semiempirical approach that combines accuracy with simplicity, a concept that has been generally neglected in previous studies. The equation is , with <jats:italic>F</jats:italic> (L), <jats:italic>K<jats:sub>s</jats:sub></jats:italic> (L/T), <jats:italic>S</jats:italic> (L<jats:italic>/</jats:italic>T<jats:sup>0.5</jats:sup>) and <jats:italic>t</jats:italic> (T) being cumulative infiltration, saturated hydraulic conductivity, sorptivity, and time, respectively. Relative errors (<jats:italic>ɛ</jats:italic>) by the application of this equation generally do not exceed ±0.3% in most applied infiltration problems faced by water resources engineering today. We show both numerically and mathematically that │<jats:italic>ɛ</jats:italic>│> 0.3% could only occur if <jats:italic>K<jats:sub>s</jats:sub>t</jats:italic>/<jats:italic>F</jats:italic> > 0.904, a criterion that could apply to sand and loamy sand soils (i.e., coarse texture) and if they experience infiltration rates for over 6 h and 19 h, respectively. Hence, we also derived a simple linear adjustment in the model as <jats:italic>F</jats:italic><jats:sub>adj</jats:sub> ≅ 0.9796 <jats:italic>F</jats:italic> + 0.335 <jats:italic>S</jats:italic><jats:sup>2</jats:sup>/<jats:italic>K<jats:sub>s</jats:sub></jats:italic> to address these longer infiltration rates, and to assure that <jats:italic>ɛ</jats:italic> remains within the expected ±0.3% range of uncertainty. A linearized regression technique was also developed to accurately estimate <jats:italic>S</jats:italic> and <jats:italic>K<jats:sub>s</jats:sub></jats:italic> when the G–A model is used. We numerically demonstrated that our fitting method could be used even when the G–A approach is less valid (diffusive soils), provided that the actual value of the capillary length (<jats:italic>λ</jats:italic>) is initially known. An added benefit of our approach is that by setting <jats:italic>λ</jats:italic> equal to 1/3 and 2/3, it can significantly limit the range of initializing, unknown, a priori values of <jats:italic>S</jats:italic> and <jats:italic>K<jats:sub>s</jats:sub></jats:italic>, as these two parameters are estimated through the inverse solution of implicit infiltration models. Due to the model's simplicity and accuracy, our solution should find application among hydrologists, natural resource scientists, and engineers who wish to easily derive accurate estimations from the G–A infiltration approach and/or estimate sorptivity and hydraulic conductivity without encountering divergence problems.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140835655","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}
Quirijn de Jong van Lier, Joshua L. Heitman, Simon Lorentz, Stanley Liphadzi, Johan van Tol
{"title":"Vadose Zone Journal Special Section: Soil physics in agricultural production, water resources, and waste management","authors":"Quirijn de Jong van Lier, Joshua L. Heitman, Simon Lorentz, Stanley Liphadzi, Johan van Tol","doi":"10.1002/vzj2.20343","DOIUrl":"https://doi.org/10.1002/vzj2.20343","url":null,"abstract":"","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140835745","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}
Sina Saneiyan, Daniel Gimenez, Ethan Siegenthaler, Lee Slater
Electrical conductivity models have been widely used to estimate water content and petrophysical properties of soils in hydrogeophysical studies. However, these models are typically only valid for soils with non‐expandable matrices because they were originally developed for clean sandstone reservoir rocks. Soils containing swelling clays are characterized by matrices that expand/contract upon gaining/losing water. In this laboratory study, we demonstrate that soil matrix changes affect saturation estimation using Archie's laws. A sample of a soil containing a swelling clay was fully saturated with a potassium chloride solution, then left to dry evaporatively at room temperature for 8 days. The complex resistivity of the soil, along with its weight and volume shrinkage, were measured daily during the drying period, and the surface conductivity was calculated based on previous empirical findings. Over the course of the study, the simultaneous evaporation yielded a 33% decrease in volume and caused a nonlinear reduction in saturation with decreasing water content. Accounting for surface conductivity and correcting for saturation using the calculated volume reduction resulted in a power‐law relationship with high R2 values between resistivity and saturation along with reasonable saturation exponents. On the contrary, neglecting either surface conductivity or shrinkage caused similar underestimations of saturation exponents. These results indicate that the application of Archie's second law to soils with swelling clays leads to erroneous predictions of resistivity if saturation values are not corrected for changes in the volume of the soil and surface conductivity is neglected.
{"title":"On the accuracy of saturation estimation from electrical measurements of soils with high swelling clay content","authors":"Sina Saneiyan, Daniel Gimenez, Ethan Siegenthaler, Lee Slater","doi":"10.1002/vzj2.20340","DOIUrl":"https://doi.org/10.1002/vzj2.20340","url":null,"abstract":"Electrical conductivity models have been widely used to estimate water content and petrophysical properties of soils in hydrogeophysical studies. However, these models are typically only valid for soils with non‐expandable matrices because they were originally developed for clean sandstone reservoir rocks. Soils containing swelling clays are characterized by matrices that expand/contract upon gaining/losing water. In this laboratory study, we demonstrate that soil matrix changes affect saturation estimation using Archie's laws. A sample of a soil containing a swelling clay was fully saturated with a potassium chloride solution, then left to dry evaporatively at room temperature for 8 days. The complex resistivity of the soil, along with its weight and volume shrinkage, were measured daily during the drying period, and the surface conductivity was calculated based on previous empirical findings. Over the course of the study, the simultaneous evaporation yielded a 33% decrease in volume and caused a nonlinear reduction in saturation with decreasing water content. Accounting for surface conductivity and correcting for saturation using the calculated volume reduction resulted in a power‐law relationship with high <jats:italic>R</jats:italic><jats:sup>2</jats:sup> values between resistivity and saturation along with reasonable saturation exponents. On the contrary, neglecting either surface conductivity or shrinkage caused similar underestimations of saturation exponents. These results indicate that the application of Archie's second law to soils with swelling clays leads to erroneous predictions of resistivity if saturation values are not corrected for changes in the volume of the soil and surface conductivity is neglected.","PeriodicalId":23594,"journal":{"name":"Vadose Zone Journal","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140835488","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}
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