scholarly journals The Effect of Willow (Salix sp.) on Soil Moisture and Matric Suction at a Slope Scale

2020 ◽  
Vol 12 (23) ◽  
pp. 9789
Author(s):  
Alejandro Gonzalez-Ollauri ◽  
Slobodan B. Mickovski
Keyword(s):  
Time Series ◽  
Soil Moisture ◽  
Soil Water ◽  
Air Temperature ◽  
Characteristic Curve ◽  
Matric Suction ◽  
Small Scale ◽  
Hillslope Hydrology ◽  
Climatic Hazards ◽  
Fallow Soil

The aim of this study is to provide new knowledge on the effect of willow on hillslope hydrology at a slope scale. Soil moisture and matric suction were monitored in situ under willow-vegetated and fallow ground covers on a small-scale hillslope in Northeast Scotland for 21 months. The retrieved time series were analysed statistically to evaluate whether the dynamics of soil moisture and matric suction changed with the hillslope zone (i.e., toe, middle, and crest) under the two ground covers. The effect of air temperature and rainfall on the dynamics of soil moisture and matric suction, as well as the relationship between the two soil-water variables, under both ground covers, were also investigated by analysing the cross-correlation between time series. The results of 21 months of monitoring showed that willow contributed substantially to reduce soil moisture and to increase matric suction with respect to fallow soil. Additionally, willow-vegetated soil exhibited higher water retention and moisture buffering capacity than fallow soil. The effect of willow was highest at the hillslope toe due to a denser vegetation cover present within this zone. Both air temperature and rainfall had a strong effect on soil moisture and matric suction. However, the effect of air temperature was more consistent and easier to interpret than that of rainfall. Soil moisture and matric suction were shown to have a complex relationship and the soil water characteristic curve for vegetated soil requires further research. This study provides novel, field-based information supporting the positive effect of willow on hillslope hydrology. The results gathered herein will undoubtedly enhance the confidence of using woody vegetation in Nature-based Solutions (NBS) against geo-climatic hazards.

A relationship describing the shear strength of unsaturated soils

1999 ◽  
Vol 36 (2) ◽  
pp. 363-368 ◽  
Author(s):  
Daud W Rassam ◽  
David J Williams
Keyword(s):  
Shear Strength ◽  
Soil Water ◽  
Nonlinear Regression ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Three Dimensional ◽  
Matric Suction ◽  
Linear Increase ◽  
Soil Water Characteristic Curve ◽  
Stress Dependent

A relationship describing the shear-strength profile of a desiccating soil deposit is essential for the purpose of analysis, especially when a numerical method is adopted where each zone in a discretised grid is assigned an elevation-dependent shear-strength value. The matric-suction profile of a desiccating soil deposit is nonlinear. Up to the air-entry value, an increase in matric suction is associated with a linear increase in shear strength. Beyond air entry, as the soil starts to desaturate, a nonlinear increase in shear strength occurs. The soil-water characteristic curve is stress dependent, as is the shear-strength gain as matric suction increases. In this paper, a three-dimensional, nonlinear regression analysis showed that a power-additive function is suitable to describe the variation of the shear strength of unsaturated soils with matric suction. The proposed function incorporates the effect of normal stress on the contribution of matric suction to the shear strength.Key words: air-entry value, matric suction, nonlinear regression, soil-water characteristic curve, tailings, unsaturated shear strength.

Soil-water characteristic curve and consolidation behavior for a compacted silt

2007 ◽  
Vol 44 (3) ◽  
pp. 266-275 ◽  
Author(s):  
Trinh Minh Thu ◽  
Harianto Rahardjo ◽  
Eng-Choon Leong
Keyword(s):  
Soil Water ◽  
Volume Change ◽  
Unsaturated Soils ◽  
Water Pressure ◽  
Characteristic Curve ◽  
Matric Suction ◽  
Confining Stress ◽  
Soil Water Characteristic Curve ◽  
Triaxial Cell ◽  
Isotropic Consolidation

Measurement of the soil-water characteristic curve (SWCC) in the laboratory is commonly conducted under zero confining pressure. However, in the field, the soil is under a confining stress. Therefore, it is important to study the effects of the confining stress on SWCC. In addition, the consolidation curve is normally generated under saturated conditions. However, the soil above the water table is usually unsaturated. Hence, it is also necessary to investigate the effects of matric suction on the characteristics of the consolidation curves. This paper presents the SWCCs under different net confining stresses and the isotropic consolidation curves under different matric suctions that describe the volume change characteristics of unsaturated soils with respect to stress state variables, net normal stress, and matric suction. A series of SWCCs was determined for statically compacted silt specimens in a triaxial cell apparatus under different net confining stresses. Isotropic consolidation tests under different matric suctions were also carried out. The results of the SWCC tests show that the air-entry value increased with increasing net confining stress. The yield points (i.e., yield suction, s0) obtained from the SWCC tests also increased with increasing net confining stress. The results of isotropic consolidation tests indicate the strong influence of matric suction on compressibility and stiffness of the compacted silt specimens.Key words: soil-water characteristic curve, isotropic consolidation, pore-water pressure, volume change, NTU mini suction probe, matric suction.

A Time-Varying Causality Formalism Based on the Liang–Kleeman Information Flow for Analyzing Directed Interactions in Nonstationary Climate Systems

2019 ◽  
Vol 32 (21) ◽  
pp. 7521-7537 ◽  
Author(s):  
Daniel Fiifi Tawia Hagan ◽  
Guojie Wang ◽  
X. San Liang ◽  
Han A. J. Dolman
Keyword(s):  
Time Series ◽  
Soil Moisture ◽  
Information Flow ◽  
Air Temperature ◽  
Land Surface ◽  
Full Range ◽  
Accurate Estimation ◽  
Time Varying ◽  
Long Time Series ◽  
Long Time

Abstract The interaction between the land surface and the atmosphere is of significant importance in the climate system because it is a key driver of the exchanges of energy and water. Several important relations to heat waves, floods, and droughts exist that are based on the interaction of soil moisture and, for instance, air temperature and humidity. Our ability to separate the elements of this coupling, identify the exact locations where they are strongest, and quantify their strengths is, therefore, of paramount importance to their predictability. A recent rigorous causality formalism based on the Liang–Kleeman (LK) information flow theory has been shown, both theoretically and in real-world applications, to have the necessary asymmetry to infer the directionality and magnitude within geophysical interactions. However, the formalism assumes stationarity in time, whereas the interactions within the land surface and atmosphere are generally nonstationary; furthermore, it requires a sufficiently long time series to ensure statistical sufficiency. In this study, we remedy this difficulty by using the square root Kalman filter to estimate the causality based on the LK formalism to derive a time-varying form. Results show that the new formalism has similar properties compared to its time-invariant form. It is shown that it is also able to capture the time-varying causality structure within soil moisture–air temperature coupling. An advantage is that it does not require very long time series to make an accurate estimation. Applying a wavelet transform to the results also reveals the full range of temporal scales of the interactions.

The Study of Correction Method for Soil-Water Characteristic Curve of Swelling-Shrinking Soil

2013 ◽  
Vol 712-715 ◽  
pp. 873-876
Author(s):  
Peng Du ◽  
Xiao Ling Liu ◽  
Xiao Ying Li
Keyword(s):  
Soil Water ◽  
Volume Fraction ◽  
Characteristic Curve ◽  
Correction Method ◽  
Matric Suction ◽  
Engineering Properties ◽  
Water Volume ◽  
Volume Deformation ◽  
Water Volume Fraction ◽  
The Relationship

The swelling-shrinking soil embodies the features of expanding when absorbing water and shrinking when drying out; its engineering properties are sensitive to water fluctuation. Mainstream test instruments of SWCC cannot accurately get its relationship between matric suction and water volume fraction. So a correction method based on the results of shrinkage test is carried out. The method is accomplished by using the volume deformation which is obtained in shrinkage test to calculate its real water volume fraction and then combining the results of SWCC test and finally constructing the relationship between matric suction and water volume fraction. Through real application, this method is proved to be feasible and essential.

scholarly journals PERANAN EKOLOGI DUSUNG DAN NON DUSUNG DAN KONTRIBUSINYA PADA KONSERVASI LINGKUNGAN DI DESA URENG KECAMATAN LEIHITU KABUPATEN MALUKU TENGAH

2018 ◽  
Vol 2 (1) ◽  
pp. 28-48
Author(s):  
Napsiah Heluth ◽  
J. Matinahoru ◽  
Fransina Latumahina
Keyword(s):  
Soil Moisture ◽  
Soil Temperature ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Air Temperature ◽  
Organic Content ◽  
Environmental Conservation ◽  
Soil Macrofauna ◽  
Organic C

The research study aims to determine the ecological conditions of dusung and non dusung, and the role of the contribution to environmental conservation in Ureng Village. The research method used was purposive sampling with observation parameters were microclimate (CO2 content, air temperature, humidity), vegetation conditions and soil conditions (soil temperature, soil moisture, soil pH, soil moisture content, soil macrofauna and organic C) . The results of  Paired of each parameter measured mostly show a smaller calculated t value compared to the t0.05 table value (1.8595) which means that the parameter is not a real difference, ie for the air humidity, t count = 0.27,; soil pH, t count = 0.6; soil macrofauna, t count = -0.66 and vegetation, t count = 1.01. As for the parameters of CO2; air temperature, soil temperature, , soil water content and organic C, t value of CO2 gives the value t count = - 16.06; air temperature = -5.11; soil temperature = -3.62; soil moisture, t count = 2,16; soil water content = 8.47, and C-Organic = 8.53; t count value which is greater than t table value which shows that there is a significant difference between CO2, air temperature, soil temperature, soil moisture, soil water content and C-Organic content in the dusung area which is greater than in the non-dusung area. From the results of the analysis it is known that dusung has a better role in environmental conservation when compared to non dusung which is indicated by the value of CO2 air temperature, soil temperature, soil moisture, soil water content and C-organic content.

scholarly journals Use of cosmic ray neutron sensors for soil moisture monitoring in forests

2015 ◽  
Vol 12 (9) ◽  
pp. 9813-9864 ◽  
Author(s):  
I. Heidbüchel ◽  
A. Güntner ◽  
T. Blume
Keyword(s):  
Time Series ◽  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Cosmic Ray ◽  
Soil Samples ◽  
Calibration Function ◽  
Neutron Sensors ◽  
Hydrogen Mass

Abstract. Cosmic ray neutron sensors (CRS) are a promising technique to measure soil moisture at intermediate scales. To convert neutron counts to average volumetric soil water content a simple calibration function can be used (the N0-calibration of Desilets et al., 2010). This calibration function is based on soil water content derived directly from soil samples taken within the footprint of the sensor. We installed a CRS in a mixed forest in the lowlands of north-eastern Germany and calibrated it 10 times throughout one calendar year. Each calibration with the N0-calibration function resulted in a different CRS soil moisture time series, with deviations of up to 0.12 m3 m-3 for individual values of soil water content. Also, many of the calibration efforts resulted in time series that could not be matched with independent in situ measurements of soil water content. We therefore suggest a new calibration function with a different shape that can vary from one location to another. A two-point calibration proved to be adequate to correctly define the shape of the new calibration function if the calibration points were taken during both dry and wet conditions covering at least 50 % of the total range of soil moisture. The best results were obtained when the soil samples used for calibration were linearly weighted as a function of depth in the soil profile and non-linearly weighted as a function of distance from the CRS, and when the depth-specific amount of soil organic matter and lattice water content was explicitly considered. The annual cycle of tree foliation was found to be a negligible factor for calibration because the variable hydrogen mass in the leaves was small compared to the hydrogen mass changes by soil moisture variations. Finally, we provide a best practice calibration guide for CRS in forested environments.

scholarly journals Use of cosmic-ray neutron sensors for soil moisture monitoring in forests

2016 ◽  
Vol 20 (3) ◽  
pp. 1269-1288 ◽  
Author(s):  
Ingo Heidbüchel ◽  
Andreas Güntner ◽  
Theresa Blume
Keyword(s):  
Time Series ◽  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Cosmic Ray ◽  
Soil Samples ◽  
Calibration Function ◽  
Total Range ◽  
Hydrogen Mass

Abstract. Measuring soil moisture with cosmic-ray neutrons is a promising technique for intermediate spatial scales. To convert neutron counts to average volumetric soil water content a simple calibration function can be used (the N0-calibration of Desilets et al., 2010). The calibration is based on soil water content derived directly from soil samples taken within the footprint of the sensor. We installed a cosmic-ray neutron sensor (CRS) in a mixed forest in the lowlands of north-eastern Germany and calibrated it 10 times throughout one calendar year. Each calibration with the N0-calibration function resulted in a different CRS soil moisture time series, with deviations of up to 0.1 m3 m−3 (24 % of the total range) for individual values of soil water content. Also, many of the calibration efforts resulted in time series that could not be matched with independent in situ measurements of soil water content. We therefore suggest a modified calibration function with a different shape that can vary from one location to another. A two-point calibration was found to effectively define the shape of the modified calibration function if the calibration points were taken during both dry and wet conditions spanning at least half of the total range of soil moisture. The best results were obtained when the soil samples used for calibration were linearly weighted as a function of depth in the soil profile and nonlinearly weighted as a function of distance from the CRS, and when the depth-specific amount of soil organic matter and lattice water content was explicitly considered. The annual cycle of tree foliation was found to be a negligible factor for calibration because the variable hydrogen mass in the leaves was small compared to the hydrogen mass changes by soil moisture variations. As a final point, we provide a calibration guide for a CRS in forested environments.

scholarly journals Microstructure of Compacted Loess and Its Influence on the Soil-Water Characteristic Curve

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Xiao Xie ◽  
Ping Li ◽  
Xiaokun Hou ◽  
Tonglu Li ◽  
Guowei Zhang
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Great Influence ◽  
Matric Suction ◽  
Constitutive Relationship ◽  
Wetting And Drying ◽  
Soil Water Characteristic Curve ◽  
High Suction ◽  
Water Contents ◽  
Compacted Loess

Soil-water characteristic curve (SWCC) is a key constitutive relationship for studying unsaturated soil, and as is known, microstructure of the soil has great influence on the mechanical behaviour of the soil. In this study, the wetting and drying soil-water characteristic curves (SWCCs) of loess compacted at three different water contents were measured using the filter paper method. And microproperties of compacted loess were obtained by the mercury intrusion method (MIP) and scanning electron microscope (SEM). Results show that the compaction water contents have significant influence on the SWCC and microstructure. The pore size distribution (PSD) curves have great differences in macropore range and are similar in micropore range. Loess compacted at optimum and dry of optimum are generally connected, while there are certain number of nonintruded pores in loess compacted at wet of optimum. The SWCC curves vary significantly in low suction (ua − uw < 1000 kPa) and tend to converge together in high suction (ua − uw ≥ 1000 kPa). Hysteresis in the SWCCs is more obvious for loess compacted at optimum and dry of optimum in the matric suction of 0∼100 kPa; however, there is a pronounced hysteresis for loess compacted at wet of optimum in full matric suction range. The characteristic of the SWCCs including their hysteresis can be well interpreted from the loess microstructure.

scholarly journals Soil-Water Characteristics of the Low Liquid Limit Silt considering Compaction and Freeze-Thaw Action

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yongsheng Yao ◽  
Shenping Luo ◽  
Junfeng Qian ◽  
Jue Li ◽  
Hongbin Xiao
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Testing Machine ◽  
Initial Moisture Content ◽  
Reference Value ◽  
Matric Suction ◽  
Liquid Limit ◽  
Freeze Thaw ◽  
Water Characteristics ◽  
Thaw Cycle

The soil-water characteristic curve of silty soil in seasonal frozen area during freezing-thawing process was studied in this study. By means of a laboratory test, specimens with different compaction degrees and different initial moisture content were prepared and put into the temperature change testing machine for freeze-thaw action. The influence of different degrees of compaction and different times of freeze-thaw action on SWCC of low liquid limit silt was analyzed, a V-G model was used to fit the test data, and a set of fitting parameters with a reference value was obtained. At the same time, the change of microstructure between soil particles during the freezing-thawing cycle is illustrated. The results showed that with the same water content and the same compactness, the matric suction of the test soil decreased with the increase of freeze-thaw cycles. For the same number of freeze-thaw cycles, the greater the compactness, the greater the matric suction of the soil. The V-G model can well represent the SWCC of low liquid limit silt during the freeze-thaw cycle.

Model for the prediction of shear strength with respect to soil suction

1996 ◽  
Vol 33 (3) ◽  
pp. 379-392 ◽  
Author(s):  
S K Vanapalli ◽  
D G Fredlund ◽  
D E Pufahl ◽  
A W Clifton
Keyword(s):  
Shear Strength ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Experimental Studies ◽  
Matric Suction ◽  
Glacial Till ◽  
Soil Suction ◽  
Soil Water Characteristic Curve

Experimental studies on unsaturated soils are generally costly, time-consuming, and difficult to conduct. Shear strength data from the research literature suggests that there is a nonlinear increase in strength as the soil desaturates as a result of an increase in matric suction. Since the shear strength of an unsaturated soil is strongly related to the amount of water in the voids of the soil, and therefore to matric suction, it is postulated that the shear strength of an unsaturated soil should also bear a relationship to the soil-water characteristic curve. This paper describes the relationship between the soil-water characteristic curve and the shear strength of an unsaturated soil with respect to matric suction. Am empirical, analytical model is developed to predict the shear strength in terms of soil suction. The formulation makes use of the soil-water characteristic curve and the saturated shear strength parameters. The results of the model developed for predicting the shear strength are compared with experimental results for a glacial till. The shear strength of statically compacted glacial till specimens was measured using a modified direct shear apparatus. Specimens were prepared at three different water contents and densities (i.e., corresponding to dry of optimum, and wet of optimum conditions). Various net normal stresses and matric suctions were applied to the specimens. There is a good correlation between the predicted and measured values of shear strength for the unsaturated soil. Key words: soil-water characteristic curve, shear strength, unsaturated soil, soil suction, matric suction.

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