scholarly journals Modelling Soil Water Dynamics from Soil Hydraulic Parameters Estimated by an Alternative Method in a Tropical Experimental Basin

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 1007 ◽  
Author(s):  
Bruno Silva Ursulino ◽  
Suzana Maria Gico Lima Montenegro ◽  
Artur Paiva Coutinho ◽  
Victor Hugo Rabelo Coelho ◽  
Diego Cezar dos Santos Araújo ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
River Basin ◽  
Time Domain Reflectometry ◽  
Water Dynamics ◽  
Hydraulic Parameters ◽  
Northeast Brazil ◽  
Mean Square Errors

Knowledge about soil moisture dynamics and their relation with rainfall, evapotranspiration, and soil physical properties is fundamental for understanding the hydrological processes in a region. Given the difficulties of measurement and the scarcity of surface soil moisture data in some places such as Northeast Brazil, modelling has become a robust tool to overcome such limitations. This study investigated the dynamics of soil water content in two plots in the Gameleira Experimental River Basin, Northeast Brazil. For this, Time Domain Reflectometry (TDR) probes and Hydrus-1D for modelling one-dimensional flow were used in two stages: with hydraulic parameters estimated with the Beerkan Estimation of Soil Transfer Parameters (BEST) method and optimized by inverse modelling. The results showed that the soil water content in the plots is strongly influenced by rainfall, with the greatest variability in the dry–wet–dry transition periods. The modelling results were considered satisfactory with the data estimated by the BEST method (Root Mean Square Errors, RMSE = 0.023 and 0.022 and coefficients of determination, R2 = 0.72 and 0.81) and after the optimization (RMSE = 0.012 and 0.020 and R2 = 0.83 and 0.72). The performance analysis of the simulations provided strong indications of the efficiency of parameters estimated by BEST to predict the soil moisture variability in the studied river basin without the need for calibration or complex numerical approaches.

Hydrological effects of combining Italian alder and blackberry in an agroforestry system in South Africa

2021 ◽  
Author(s):  
Svenja Hoffmeister ◽  
Rafael Bohn Reckziegel ◽  
Florian Kestel ◽  
Rebekka Maier ◽  
Jonathan P. Sheppard ◽  
...  
Keyword(s):  
South Africa ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Budget ◽  
Time Domain Reflectometry ◽  
Water Dynamics ◽  
Matrix Potential ◽  
Local Soil ◽  
Hydrological Effects

<p>Water limitation provides the potential to hinder the productivity of agricultural systems especially in arid and semi-arid regions. In agroforestry systems interactions between trees and crops range from mutually beneficial to critically competing, shaping the demand for resources, such as water. In this study, we investigated the hydrological effects of an Italian Alder (Alnus cordata) windbreak on an irrigated blackberry plantation near Stellenbosch, South Africa. We determine the key components of the water budget in the system and compare them at two positions: alongside the windbreak, and amongst the crop away from the windbreak’s influence.</p><p>We measured soil water content depth profiles in the summer months, from October 2019 to March 2020, in both locations with four consecutive time domain reflectometry (TDR) tube sensors, each integrating over 20 cm depth. Potential evapotranspiration (ET) was estimated from site based meteorological observations. We surveyed and classified the local soil, and defined soil chemical and physical properties (e.g. texture, matrix potential). The windbreak structure was measured on a single tree basis (e.g. tree height, volume and biomass) using manual and terrestrial laser scanning methodologies.</p><p>The data indicate that high potential ET, caused by high summer temperatures and strong winds, dominates the water budget at the study site, exceeding the water input of the drip irrigation. We found differences in the water dynamics between the two sites, e.g. greater soil water content at greater distances from the windbreak. Possible reasons are: (1) the water demand of trees increases underground competition for water, and/or; (2) microclimatic conditions closer to the windbreak increase ET. Modelling of the windbreak influence on the ET and further analysis of water fluxes will be conducted as next steps to combine the results from the sensors and the joint field campaign.</p>

scholarly journals Soil Moisture Retrieval Model for Remote Sensing Using Reflected Hyperspectral Information

2019 ◽  
Vol 11 (3) ◽  
pp. 366 ◽  
Author(s):  
Jing Yuan ◽  
Xin Wang ◽  
Chang-xiang Yan ◽  
Shu-rong Wang ◽  
Xue-ping Ju ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Temporal Distribution ◽  
Rapid Test ◽  
Retrieval Model ◽  
Validity And Reliability ◽  
Validation Set ◽  
Mean Square Errors

The variation and the spatial–temporal distribution of soil water content have significant effects on heat balance, agricultural moisture, etc. A soil moisture (SM) retrieval model can provide a theoretical basis for realizing a rapid test and revealing the spatial–temporal variation of the surface water. However, remote sensors do not measure soil water content directly. Therefore, it is of great importance to establish a SM retrieval model. In this paper, the relationship between SM and diffuse reflectance was first derived using the absorption coefficient and scattering coefficient related to SM. Then, based on Kubelka–Munk (KM) theory, the SM retrieval model using reflectance information was further derived, which is a semi-empirical model with an unknown parameter obtained either from fitting or from experimental measurements. The validity and reliability of the model were confirmed with the validation set. The results showed that the root mean square errors of prediction (RMSEPs) of four soils were generally less than 0.017, while the coefficients of determination (R2s) of four soils were generally more than 0.85, and the ratios of the performance to deviation (RPDs) of four soils were greater than 2.5 (470–2400 nm). Therefore, the model has high prediction accuracy, and can be well applied to the prediction of water content in different sorts of soils.

Evaluation of NMR and other soil water content measurement methods at the point and field scale

2020 ◽  
Author(s):  
Matteo Bauckholt ◽  
Marco Pohle ◽  
Martin Schrön ◽  
Steffen Zacharias ◽  
Solveig Landmark ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Column ◽  
Cosmic Ray ◽  
Time Domain Reflectometry ◽  
Measurement Methods ◽  
Hydrogen Atoms ◽  
Conventional Methods

<p>Soil water content in the unsaturated zone is a key parameter of the environmental system. The understanding of soil moisture plays a major role with regard to questions of water and nutrient supply to plants, groundwater recharge, soil genesis and climatic interactions.</p><p>In our study we aim to test a new technology for the non-invasive measurement of soil moisture profiles, the so-called Surface-NMR (Nuclear Magnetic Resonance). The instrument applies magnetic fields to the ground and detects its changes caused by mobile and immobile hydrogen atoms in the soil column. Using four different frequencies, the data may provide insights into the water content of four distinct soil layers between the surface and 20 cm depth.</p><p>We carried out multiple NMR measurements at four different field sites in Germany and compared the data with conventional methods, such as gravimetric soil samples, Time Domain Reflectometry (TDR), and Cosmic-Ray Neutron Sensing (CRNS).</p><p>The dataset will be used to investigate the following research questions:</p><ol><li>Is the Surface-NMR method suitable to provide depth-resolved information of soil moisture under field conditions?</li> <li>Does Surface-NMR have the potential to replace or complement conventional methods of soil moisture measurement in the field?</li> <li>What can we learn about the spatial variability and scale dependency of soil moisture by combining three measurement methods of different scale (TDR, NMR, CRNS)?</li> </ol>

Precision and accuracy of three alternative instruments for measuring soil water content in two forest soils of the Pacific Northwest

2005 ◽  
Vol 35 (8) ◽  
pp. 1867-1876 ◽  
Author(s):  
Nicole M Czarnomski ◽  
Georgianne W Moore ◽  
Tom G Pypker ◽  
Julian Licata ◽  
Barbara J Bond
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Pacific Northwest ◽  
Lower Cost ◽  
Time Domain Reflectometry ◽  
Calibration Equation ◽  
Accuracy And Precision ◽  
The Pacific

We compared the accuracy and precision of three devices for measuring soil water content in both natural and repacked soils and evaluated their temperature sensitivity. Calibrations were developed for a capacitance instrument (ECH2O), a time domain reflectometry cable tester (CT), and a water content reflectometer (WCR) in soils collected from the Wind River and H.J. Andrews Experimental Forests. We compared these calibrations with equations suggested by manufacturers or commonly used in the literature and found the standard equations predicted soil moisture content 0%–11.5% lower (p < 0.0001) than new calibrations. Each new calibration equation adequately predicted soil moisture from the output for each instrument regardless of location or soil type. Prediction intervals varied, with errors of 4.5%, 3.5%, and 7.1% for the ECH2O, CT, and WCR, respectively. Only the ECH2O system was significantly influenced by temperature for the range sampled: as temperature increased by 1 °C, the soil moisture estimate decreased by 0.1%. Overall, the ECH2O performed nearly as well as the CT, and thanks to its lower cost, small differences in performance might be offset by deployment of a greater number of probes in field sampling. Despite its higher cost, the WCR did not perform as well as the other two systems.

scholarly journals Analysis of soil water dynamics in an agroforestry system based on detailed soil water records from time-domain reflectometry

1999 ◽  
Vol 3 (4) ◽  
pp. 517-527 ◽  
Author(s):  
N. A. Jackson ◽  
J. C. Wallace
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Time Domain ◽  
Agroforestry System ◽  
Time Domain Reflectometry ◽  
Water Dynamics ◽  
Spatial And Temporal Variation ◽  
Soil Water Dynamics ◽  
Tree Canopies

Abstract. Time domain reflectometry [TDR] was used to investigate the spatial and temporal variation in surface soil water dynamics under a number of types of vegetation, including both trees and crops grown in isolation, and grown together as an agroforestry system. The installation and operation of this technique are presented, and discussed in terms of its suitability to monitor rapid fluctuations in soil-water content in a spatially heterogeneous system such as that described in this experiment. The relatively small sampling volume of each of the TDR waveguides permitted discrete measurements to be made of soil water content (θv). In the tree-only and tree+crop treatments, this revealed considerable variation in θv resulting from spatial redistribution of rainfall under the tree canopies, with a significant input to soil close to the base of the trees being made by stemflow, i.e. water intercepted by the tree canopy and channelled down the stem. Over the experimental period (one rainy season) the TDR data suggested that net recharge to the soil profile in the sole crop system was 53 mm, almost 75% more than occurred in either of the two treatments containing trees, reflecting greater rainfall interception by the tree canopies.

A simple method for soil moisture calculation using data from ELBARA III passive radiometer and thermal inertia

2020 ◽  
Author(s):  
Mateusz Lukowski ◽  
Lukasz Gluba ◽  
Anna Rafalska-Przysucha ◽  
Kamil Szewczak ◽  
Bogusław Usowicz
Keyword(s):  
Heat Capacity ◽  
Soil Moisture ◽  
Brightness Temperature ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Thermal Inertia ◽  
Time Domain Reflectometry ◽  
L Band

&lt;p&gt;The soil is a heterogonous substance consists of three phases: solid, gas and liquid, where the latter is mainly water &amp;#8211; the natural solvent with very high heat capacity. Due to this physical property and the fact that water is a common substance on our planet, it has a significant impact for stability of the climate on Earth. Another water property, the dielectric constant much higher than in other soil ingredients, is often used to determine soil water content. As an example, the Time Domain Reflectometry (TDR) technique for in situ soil moisture measurements may be mentioned. For soil moisture assessments at global scale, the satellite-based instruments were designed and launched into space, e.g. Soil Moisture and Ocean Salinity (SMOS) or Soil Moisture Active Passive (SMAP). Those satellites are measuring brightness temperature of soil in microwave (L-band) domain. The algorithms that retrieve soil moisture from L-band measurements by nonlinear optimisation engage several parameters such as soil temperature, its roughness and vegetation cover. In the presented work, we introduce a much simpler method that base on three facts: i) a high water heat capacity cause that, during the diurnal night/day cycle, the soil with higher water content cools down and heats up slower than dry soil. This phenomenon was quantified by thermal inertia; ii) brightness temperature is related to the effective temperature of the surface and iii) plants are generally semi-transparent for L-band microwaves, what gives a possibility for probing soil properties underneath vegetation. Due to iii) we assumed that L-band soil albedo (needed in thermal inertia computations) is constant. The proposed approach seems to be reasonable, as both variables, brightness temperature and thermal inertia, strongly depend on soil water content. The method was evaluated using ELBARA (European Space Agency L-band Radiometer) instrument operating at Bubnow test site in Poland. The ELBARA is a directional receiver at 1.4 GHz frequency (the same as received by SMOS satellite), installed on the Earth&amp;#8217;s surface, at 6-meter tower. In the years 2016-2019, we conducted 16 field campaigns &amp;#8211; we measured surface soil moisture in situ using TDR, and interpolate it to semi-continuous grid using geostatistics. Then, the driest and the wettest points (in space and time) were chosen and assigned to, respectively, maximum and minimum thermal inertia. Basing on that, the model retrieving soil moisture was built, and the other measurements served as validation assembly. Simple regression methods revealed good or moderately good agreement between modelled and measured data. Some outliers, probably induced by meteorological phenomena disturbing stable soil cooling and heating such as rain or wind, have been noticed.&lt;/p&gt;&lt;p&gt;Research was partially conducted under the project &amp;#8220;Water in soil - satellite monitoring and improving the retention using biochar&amp;#8221; no. BIOSTRATEG3/345940/7/NCBR/2017 which was financed by Polish National Centre for Research and Development in the framework of &amp;#8220;Environment, agriculture and forestry&amp;#8221; &amp;#8211; BIOSTRATEG strategic R&amp;D programme.&lt;/p&gt;

scholarly journals ESTIMATES OF SOIL WATER CONTENT USING GROUND PENETRATING RADAR IN FIELD CONDITIONS

2015 ◽  
Vol 33 (3) ◽  
pp. 389 ◽  
Author(s):  
Marcelo Jorge Luz Mesquita ◽  
José Gouvêa Luiz ◽  
José de Paulo Rocha da Costa
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Wave Velocity ◽  
Ground Penetrating Radar ◽  
Time Domain Reflectometry ◽  
Field Conditions ◽  
Calibration Equation ◽  
Ground Penetrating

ABSTRACT. Electromagnetic methods play an important role in the study of soil water content, mainly because electromagnetic properties in the shallow subsurface area are primarily controlled by the presence of water. This work analyzes the effectiveness of Ground Penetrating Radar (GPR) as a tool for estimating soil water content in field conditions, introduces a calibration equation to estimate average soil moisture of the area studied from the analysis of GPR wave velocity, and evaluates the process used to create it. Methodologies for collecting GPR data seeking the determination of soil moisture from the velocity of the electromagnetic wave and the use of equations proposed in the literature, Topp and Roth, are also discussed. The GPR common-offset methodology (400 MHz antennas) was utilized in a study in Cuiarana, Salin´opolis, Par´a State, in northern Brazil and the resulting data compared with data from TDR (Time Domain Reflectometry) (0.12 m double probe) methodology. The data were then statistically analyzed enabling the establishment of a calibration equation for water content determination in terms of electromagnetic wavevelocity obtained with GPR. The study successfully showed the feasibility and limitations of estimating water content using GPR. Also is discussed the possibility of calibration equation to the soil water content analysis with GPR data using, as parameter, data obtained by other indirect method, in this case, the TDR.Keywords: soil water content, relative permittivity, GPR, TDR, wave velocity. RESUMO. Os métodos eletromagnéticos são uma importante ferramenta no estudo da umidade do solo, principalmente porque as propriedades eletromagnéticas da subsuperfície rasa são controladas pela presença de água. Este trabalho, além de analisar a eficácia do Radar de Penetração no Solo (GPR) como ferramenta de medição da umidade do solo in situ sob condições de campo não controladas, introduz uma equação de calibração para estimar a umidade do solo da área estudada a partir da análise da velocidade da onda do GPR e avalia o processo da sua criação. São também discutidas as metodologias comumente empregadas na coleta de dados com o GPR, visando a determinação da umidade do solo a partir da velocidade da onda eletromagnética, assim como a utilização das equações propostas na literatura, Topp e Roth. A metodologia common-offset (GPR com antenas de 400 MHz) foi empregada em um estudo realizado em Cuiarana, município de Salinópolis, Pará, no norte do Brasil e os dados comparados com medidas de umidade realizadas com TDR (sonda dupla de 0,12 m). Os dados foram estatisticamente correlacionados permitindo o estabelecimento de uma equação de calibração para a determinação de umidade em termos da velocidade da onda eletromagnética obtida com o GPR. O estudo demonstrou com sucesso a viabilidade, a rapidez e as limitações do GPR na estimativa do conteúdo de água no solo. Também é discutida a possibilidade da calibração de equação para análise de umidade com o GPR usando como parâmetro dados obtidos por outro método indireto, neste caso, o TDR.Palavras-chave: umidade do solo, permissividade relativa, GPR, TDR, velocidade da onda.

Measuring Soil Water Content With Time Domain Reflectometry

Soil Science ◽  
2010 ◽  
Vol 175 (10) ◽  
pp. 469-473 ◽  
Author(s):  
Zhaoqiang Ju ◽  
Xiaona Liu ◽  
Tusheng Ren ◽  
Chunsheng Hu
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Time Domain ◽  
Time Domain Reflectometry

scholarly journals Relating surface backscatter response from TRMM Precipitation Radar to soil moisture: results over a semi-arid region

2009 ◽  
Vol 6 (5) ◽  
pp. 6425-6454
Author(s):  
H. Stephen ◽  
S. Ahmad ◽  
T. C. Piechota ◽  
C. Tang
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Arid Regions ◽  
Vegetation Index ◽  
Temporal Trends ◽  
Model Parameters ◽  
Precipitation Radar ◽  
Semi Arid

Abstract. The Tropical Rainfall Measuring Mission (TRMM) carries aboard the Precipitation Radar (TRMMPR) that measures the backscatter (σ°) of the surface. σ° is sensitive to surface soil moisture and vegetation conditions. Due to sparse vegetation in arid and semi-arid regions, TRMMPR σ° primarily depends on the soil water content. In this study we relate TRMMPR σ° measurements to soil water content (ms) in Lower Colorado River Basin (LCRB). σ° dependence on ms is studied for different vegetation greenness values determined through Normalized Difference Vegetation Index (NDVI). A new model of σ° that couples incidence angle, ms, and NDVI is used to derive parameters and retrieve soil water content. The calibration and validation of this model are performed using simulated and measured ms data. Simulated ms is estimated using Variable Infiltration Capacity (VIC) model whereas measured ms is acquired from ground measuring stations in Walnut Gulch Experimental Watershed (WGEW). σ° model is calibrated using VIC and WGEW ms data during 1998 and the calibrated model is used to derive ms during later years. The temporal trends of derived ms are consistent with VIC and WGEW ms data with correlation coefficient (R) of 0.89 and 0.74, respectively. Derived ms is also consistent with the measured precipitation data with R=0.76. The gridded VIC data is used to calibrate the model at each grid point in LCRB and spatial maps of the model parameters are prepared. The model parameters are spatially coherent with the general regional topography in LCRB. TRMMPR σ° derived soil moisture maps during May (dry) and August (wet) 1999 are spatially similar to VIC estimates with correlation 0.67 and 0.76, respectively. This research provides new insights into Ku-band σ° dependence on soil water content in the arid regions.

Root effects on soil water and hydraulic properties

Biologia ◽  
2007 ◽  
Vol 62 (5) ◽  
Author(s):  
Horst Gerke ◽  
Rolf Kuchenbuch
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Water Content ◽  
Bulk Density ◽  
Soil Water ◽  
Soil Water Content ◽  
Hydraulic Properties ◽  
Soil Hydraulic Properties ◽  
Soil Hydraulic ◽  
Root Effects

AbstractPlants can affect soil moisture and the soil hydraulic properties both directly by root water uptake and indirectly by modifying the soil structure. Furthermore, water in plant roots is mostly neglected when studying soil hydraulic properties. In this contribution, we analyze effects of the moisture content inside roots as compared to bulk soil moisture contents and speculate on implications of non-capillary-bound root water for determination of soil moisture and calibration of soil hydraulic properties.In a field crop of maize (Zea mays) of 75 cm row spacing, we sampled the total soil volumes of 0.7 m × 0.4 m and 0.3 m deep plots at the time of tasseling. For each of the 84 soil cubes of 10 cm edge length, root mass and length as well as moisture content and soil bulk density were determined. Roots were separated in 3 size classes for which a mean root porosity of 0.82 was obtained from the relation between root dry mass density and root bulk density using pycnometers. The spatially distributed fractions of root water contents were compared with those of the water in capillary pores of the soil matrix.Water inside roots was mostly below 2–5% of total soil water content; however, locally near the plant rows it was up to 20%. The results suggest that soil moisture in roots should be separately considered. Upon drying, the relation between the soil and root water may change towards water remaining in roots. Relations depend especially on soil water retention properties, growth stages, and root distributions. Gravimetric soil water content measurement could be misleading and TDR probes providing an integrated signal are difficult to interpret. Root effects should be more intensively studied for improved field soil water balance calculations.

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