Unsaturated Zone: Advances in Experimental and Theoretical Investigations

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydrology".

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 14554

Special Issue Editor


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Guest Editor
CNR National Research Council, IRSA Water Research Institute, via Francesco De Blasio 5, 70132 Bari, Italy
Interests: unsaturated zone; hydrogeology; hydrogeophysics; field and laboratory tests for hydraulic characterization of rock and soil; critical zone investigation; water resources management; sensors development; environmental monitoring; MAR; porous rocks

Special Issue Information

Dear Colleagues,

The unsaturated zone has a crucial role in subsurface processes that, in turn, impact soil moisture, groundwater quality and quantity, and ecosystem function. Different theoretical and experimental approaches have been developed to increase the knowledge of this portion of the subsurface, but still there are gaps in comprehension and quantification of the processes that occur in the unsaturated zone. The purpose of this Special Issue is to collect and publish the most recent research concerning both the theretical and experimental studies, aiming to increase knowledge of how fluids and susbstances move in the unsaturated zone differently from the traditional theories and tools. Papers dealing with preferential flow are particularly welcome, including new experimental observation tools for their evidence and new theoretical formulation for their prediction.  Additionally, studies other than those mentioned are welcome  in order to provide a valuable overview of the newest approaches used and to better undestand the various mechanisms that act in different situations in the unsaturated zone.

Dr. Maria Clementina Caputo
Guest Editor

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Keywords

  • unsaturated zone
  • preferential flow
  • experimental evidence
  • unsaturated flow
  • new conceptualization
  • experimental tests

Published Papers (7 papers)

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Editorial

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3 pages, 160 KiB  
Editorial
Unsaturated Zone: Advances in Experimental and Theoretical Investigations
by Maria Clementina Caputo
Water 2023, 15(4), 675; https://doi.org/10.3390/w15040675 - 9 Feb 2023
Cited by 1 | Viewed by 1117
Abstract
The unsaturated zone has a crucial role in subsurface processes that, in turn, impact soil moisture, groundwater quality and quantity, and ecosystem function [...] Full article

Research

Jump to: Editorial

13 pages, 2520 KiB  
Article
Time-Lapse ERT, Moment Analysis, and Numerical Modeling for Estimating the Hydraulic Conductivity of Unsaturated Rock
by Lorenzo De Carlo, Mohammad Farzamian, Antonietta Celeste Turturro and Maria Clementina Caputo
Water 2023, 15(2), 332; https://doi.org/10.3390/w15020332 - 12 Jan 2023
Cited by 2 | Viewed by 2172
Abstract
In recent years, geophysical techniques have been increasingly used to monitor flow and transport processes in the Earth critical zone (ECZ). Among these, electrical resistivity tomography (ERT) is a powerful tool used to predict hydrological parameters and state variables that influence the mentioned [...] Read more.
In recent years, geophysical techniques have been increasingly used to monitor flow and transport processes in the Earth critical zone (ECZ). Among these, electrical resistivity tomography (ERT) is a powerful tool used to predict hydrological parameters and state variables that influence the mentioned processes in the vadose zone because of the strong correlation between electrical and hydrological properties of the filtering medium. There have been many field tests considering geophysical prospecting in soils, where point scale hydrological sensors measurements are typically collected through sensors for geophysical data validation; on the contrary, when the unsaturated zone is made of hard rocks, the installation of such sensors is not a trivial issue owing to the extreme difficulties to guarantee contact between sensors and the surrounding medium. In this context, the geophysical data combined with appropriate numerical analysis techniques can effectively overcome the lack of information of the unsaturated subsurface, which is otherwise unpredictable with traditional methods. In the proposed case study, hydrogeophysical data were collected to provide a quantitative estimation of the hydraulic conductivity of sandstone through an integrated approach based on the moment analysis technique and numerical modeling. Full article
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20 pages, 4591 KiB  
Article
The Application and Improvement of Soil–Water Characteristic Curves through In Situ Monitoring Data in the Plains
by Pingnan Zhang, Gang Chen, Jinning Wu, Chuanhai Wang, Shiwei Zheng, Yue Yu, Youlin Li and Xiaoning Li
Water 2022, 14(24), 4012; https://doi.org/10.3390/w14244012 - 8 Dec 2022
Cited by 2 | Viewed by 1636
Abstract
In order to study the soil–water characteristic curve and soil–water movement in the unsaturated zone of the humid plain area and investigate its influence on the regional water cycle process, this study conducted a long series of hydrometeorological data monitoring on the whole [...] Read more.
In order to study the soil–water characteristic curve and soil–water movement in the unsaturated zone of the humid plain area and investigate its influence on the regional water cycle process, this study conducted a long series of hydrometeorological data monitoring on the whole process of precipitation, evaporation, soil water content, pore water pressure and depth of groundwater level at the Jintan field hydrological test in the plain area of the Taihu Basin, China. Based on the collected data, the soil water dynamic at different depths was analyzed, and the results showed that the soil water fluctuated most frequently and drastically at a soil horizon depth of 0–40 cm, with an obvious soil moisture wetting and drying cycle. The van Genuchten model (VG model) was used to describe the soil–water characteristic curve, and the parameters of the VG model were obtained by numerical inversion of field monitoring data using numerical code (HYDRUS-1D). The obtained parameters were used to simulate soil water movement in each soil horizon for six precipitation events and were compared with the simulation results of laboratory data. The study shows that the soil water simulation based on field data is better, which verifies the accuracy and reliability of the VG model obtained from field observation and provides a reliable theoretical basis for soil water movement and the calculation of runoff yield in the plain area of the Taihu Basin. Full article
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22 pages, 7281 KiB  
Article
Evaluation of Soil-Water Characteristic Curve and Pore-Size Distribution of Fine-Grained Soils
by Kadir Kocaman, Askin Ozocak, Tuncer B. Edil, Ertan Bol, Sedat Sert, Kurban Onturk and Mustafa Ozsagir
Water 2022, 14(21), 3445; https://doi.org/10.3390/w14213445 - 29 Oct 2022
Cited by 7 | Viewed by 2891
Abstract
A soil’s physical properties, mineral types, and pore structure significantly influence the shape and properties of the soil-water characteristic curve (SWCC). This study investigated the effects of the soil’s physical properties and mineral types on the SWCC and pore-size distribution (PSD). Eight different [...] Read more.
A soil’s physical properties, mineral types, and pore structure significantly influence the shape and properties of the soil-water characteristic curve (SWCC). This study investigated the effects of the soil’s physical properties and mineral types on the SWCC and pore-size distribution (PSD). Eight different soils from an alluvial deposit in Istanbul and Adapazarı/Türkiye were used in the study. The test samples were prepared by compaction at optimum water content (OWC) and wet side of optimum water content (wet of OWC). The samples were prepared by consolidation from the slurry. The PSDs of the samples were calculated using the SWCCs and evaluated with scanning electron microscope (SEM) analysis. In addition, the mineral types of all soils were determined by X-ray diffraction analysis. The soil which contains illite-type minerals has higher matric suction than containing kaolin-type. The effect of the clay percentage is more pronounced in silty soils than in plasticity and activity. Soil suction increased with decreasing compaction water content in clayey soils. The air entry water contents rose as the void ratio, liquid limit, clay content, and plasticity increased. The compaction conditions affected the macropore structure more than the micropore structure. In addition, the ratio of macro-micro pore sizes increased with the rise of the compaction water content. Full article
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11 pages, 1412 KiB  
Article
HYPROP-FIT to Model Rock Water Retention Curves Estimated by Different Methods
by Maria Clementina Caputo, Lorenzo De Carlo and Antonietta Celeste Turturro
Water 2022, 14(21), 3443; https://doi.org/10.3390/w14213443 - 29 Oct 2022
Cited by 6 | Viewed by 1834
Abstract
The water retention curve, which relates the matric potential, ψ, to the water content, θ, is essential to describe the flow processes in the unsaturated zone and provides useful information for environmental and engineering applications. There are few studies devoted to [...] Read more.
The water retention curve, which relates the matric potential, ψ, to the water content, θ, is essential to describe the flow processes in the unsaturated zone and provides useful information for environmental and engineering applications. There are few studies devoted to measuring the rock water retention curves due to the rock’s tightness, which makes it more technically difficult to use specific methods. In this study, we tested four different methods to measure water retention curves of two lithotypes of carbonate porous rocks with the aim to find the most effective to be applied to rock samples. Suction table, evaporation, Quasi-Steady Centrifuge, and WP4-T dewpoint potentiameter methods have been applied. The Quasi-Steady Centrifuge method proved to be the only one capable of determining water retention curves in the entire water content range and capturing the bimodality of the tested media with respect to the other methods. The measured water retention data were fitted with HYPROP-FIT software that allows us to accurately describe the WRCs and obtain critical parameters for the numerical simulation of flow and transport through the vadose zone, which plays a key role in various environmental issues. Full article
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10 pages, 430 KiB  
Article
Order Out of Chaos in Soil–Water Retention Curves
by Lucas Parreira de Faria Borges, André Luís Brasil Cavalcante and Luan Carlos de Sena Monteiro Ozelim
Water 2022, 14(15), 2421; https://doi.org/10.3390/w14152421 - 4 Aug 2022
Cited by 1 | Viewed by 1613
Abstract
Water flow in porous media is one of many phenomena in nature that can demonstrate both simple and complex behaviors. A soil–water retention curve (SWRC) is needed to characterize this flow properly. This curve relates the soil water content and the matric potential [...] Read more.
Water flow in porous media is one of many phenomena in nature that can demonstrate both simple and complex behaviors. A soil–water retention curve (SWRC) is needed to characterize this flow properly. This curve relates the soil water content and the matric potential (or porepressure), being fundamental for simulating unsaturated soil behaviors. This article proposes a new model based on simple assumptions regarding the saturated and unsaturated branches of soil–water retention curves. Despite its simplicity, the modeling capability of the proposed SWRC is shown for two types of soil. This new SWRC is obtained as a logistic function after solving an ordinary differential equation (ODE). This ODE can also be solved numerically using the Finite Difference Method (FDM), which indicates that the discrete version of the SWRC can be represented as the logistic map for specific parameters. On the other hand, this discrete representation is known to encompass chaotic and fractal behaviors. This link is used to investigate the stability and convergence of the FDM scheme, indicating that for values pre-bifurcation, both the FDM and the analytical solution of the ODE represent the new SWRC. This way, the present paper is the first step to better understating how a chaotic framework could be related to SWRCs and geotechnics in general. Full article
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21 pages, 2226 KiB  
Article
Implications of Hysteresis on the Horizontal Soil Water Redistribution after Infiltration
by George Kargas, Konstantinos X. Soulis and Petros Kerkides
Water 2021, 13(19), 2773; https://doi.org/10.3390/w13192773 - 6 Oct 2021
Cited by 6 | Viewed by 2155
Abstract
Although soil water redistribution is critical for a number of problems, a rather limited study of this process has been reported up to now and especially as regards the implications of hysteresis on horizontal soil water redistribution after infiltration. To this end, a [...] Read more.
Although soil water redistribution is critical for a number of problems, a rather limited study of this process has been reported up to now and especially as regards the implications of hysteresis on horizontal soil water redistribution after infiltration. To this end, a thorough theoretical and numerical investigation of the redistributed soil water content profiles formed after the cessation of a horizontal infiltration is presented. A number of different initial soil water contents before the initiation of the horizontal infiltration and different infiltration depths were analyzed using the HYDRUS-1D software package considering the appropriate hysteretic wetting and drying curves. The effect of neglecting hysteresis was also investigated for the same conditions. The main wetting and drying boundary curves of the studied porous medium and the hydraulic conductivity at saturation were experimentally determined. The theoretical and numerical analysis indicated that the form of the redistributed soil water content profiles in the presence of hysteresis was similar to the original infiltration profile independently of whether the initial soil water content was taken on the boundary wetting or drying curve and independently of the porous medium type. Specifically, in a relatively short time after the initiation of the redistribution process, the magnitude of the soil matrix head gradient tended to zero due to hysteresis, and this resulted in an insignificant soil water movement, although the soil water content and the hydraulic conductivity values were still high. In addition, the redistribution proceeded at a faster rate than the smallest depth of infiltration water prior to the redistribution, and it was faster during the early stages of the redistribution. Accordingly, hysteresis is important for the simulation of horizontal soil water redistribution as it is, for example, in the case of localized irrigation systems’ design and management. Full article
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