Using High-Resolution Soil Moisture Data to Assess Soil Water Dynamics in the Vadose Zone

Abstract BackgroundSubsurface irrigation has been confirmed to have high water use efficiency due to it irrigating only the crop root zone. Hydrotropism allows roots to grow towards higher water content areas for drought avoidance, which has research interests in recent years. However, most hydrotropism studies focused on a single root and were conducted in air or agar systems. The performance of hydrotropism in subsurface irrigation is not clear. ResultsWe developed a method to observe and analyze hydrotropism in soil under water-saving cultivation. A wet zone was produced around the whole root system based on using subsurface irrigation method and micro soil water dynamics were observed using high-resolution soil moisture sensors. This method enabled the observation and analysis of plant water absorption activities and the hydrotropic response of the root system. In the analysis, we first applied a high-pass filter and fast Fourier transform to the soil water dynamics data. The results indicated that the plant’s biological rhythm of photosynthetic activities can be identified from the soil moisture data. We then observed root growth in response to the dynamics of soil water content in the wet zone. We quantified root distribution inside and outside the wet zone and observed the shape of the root system from the cross-section of the wet zone. The results showed that the root hydrotropic response is not uniform for all roots of an individual plant. ConclusionsThis study verified the feasibility of using high-resolution soil moisture sensors to study root hydrotropic responses in soil during water-saving cultivation. To further evaluate a plant’s hydrotropic ability, it is necessary to use statistical analysis and/or a non-deterministic approach. Future studies may also explore developing an automated experimental system and robotic manipulations for getting steady repeatable observation of hydrotropism in water-saving cultivation.

Download Full-text

A laboratory study of the effect of soil-water dynamics on the migration of gases from subsurface sources

10.5194/egusphere-egu21-6101 ◽

2021 ◽

Author(s):

Ana M. C. Ilie ◽

Tissa H. Illangasekare ◽

Kenichi Soga ◽

William R. Whalley

Keyword(s):

Soil Moisture ◽

Soil Water ◽

Sandy Soil ◽

Land Surface ◽

Soil Gas ◽

Water Dynamics ◽

Gas Migration ◽

Soil Water Dynamics ◽

Scale Test ◽

Properties Of Soil

<p>Understanding the soil-gas migration in unsaturated soil is important in a number of problems that include carbon loading to the atmosphere from the bio-geochemical activity and leakage of gases from subsurface sources from carbon storage unconventional energy development. The soil water dynamics in the vadose zone control the soil-gas pathway development and, hence, the gas flux's spatial and temporal distribution at the soil surface. The spatial distribution of soil-water content depends on soil water characteristics. The dynamics are controlled by the water flux at the land surface and water table fluctuations. Physical properties of soil give a better understanding of the soil gas dynamics and migration from greater soil depths. The fundamental process of soil gas migration under dynamic water content was investigated in the laboratory using an intermediate-scale test system under controlled conditions that is not possible in the field. The experiments focus on observing the methane gas migration in relation to the physical properties of soil and the soil moisture patterns. A 2D soil tank with dimensions of 60 cm &#215; 90 cm &#215; 5.6 cm (height &#215; length &#215; width) was used.&#160; The tank was heterogeneously packed with sandy soil along with a distributed network of soil moisture, temperature, and electrical conductivity sensors. The heterogeneous soil configuration was designed using nine uniform silica sands with the effective sieve numbers #16, #70, #8, #40/50, #110, #30/40, #50, and #20/30 (Accusands, Unimin Corp., Ottawa, MN), and a porosity ranging in values from 0.31 to 0.42. Four methane infrared gas sensors and a Flame Ionization detector (HFR400 Fast FID) were used for the soil gas sampling at different depths within the soil profiles and at the land surface.&#160; A complex transient soil moisture distribution and soil gas migration patterns were observed in the 2D tank. These processes were successfully captured by the sensors. These preliminary experiments helped us to understand the mechanism of soil moisture sensor response and methane gas migration into a heterogeneous sandy soil with a view to developing a large-scale test in a 3D tank (4.87 m &#215; 2.44 m &#215; 0.40 m) and finally transition to field deployment.</p>

Download Full-text

Quantitative high-resolution observations of soil water dynamics in a complicated architecture using time-lapse ground-penetrating radar

Hydrology and Earth System Sciences ◽

10.5194/hess-19-1125-2015 ◽

2015 ◽

Vol 19 (3) ◽

pp. 1125-1139 ◽

Cited By ~ 22

Author(s):

P. Klenk ◽

S. Jaumann ◽

K. Roth

Keyword(s):

High Resolution ◽

Water Content ◽

Soil Water ◽

Ground Penetrating Radar ◽

Time Lapse ◽

Test Site ◽

Water Dynamics ◽

Soil Water Dynamics ◽

Capillary Fringe ◽

Ground Penetrating

Abstract. High-resolution time-lapse ground-penetrating radar (GPR) observations of advancing and retreating water tables can yield a wealth of information about near-surface water content dynamics. In this study, we present and analyze a series of imbibition, drainage and infiltration experiments that have been carried out at our artificial ASSESS test site and observed with surface-based GPR. The test site features a complicated but known subsurface architecture constructed with three different kinds of sand. It allows the study of soil water dynamics with GPR under a wide range of different conditions. Here, we assess in particular (i) the feasibility of monitoring the dynamic shape of the capillary fringe reflection and (ii) the relative precision of monitoring soil water dynamics averaged over the whole vertical extent by evaluating the bottom reflection. The phenomenology of the GPR response of a dynamically changing capillary fringe is developed from a soil physical point of view. We then explain experimentally observed phenomena based on numerical simulations of both the water content dynamics and the expected GPR response.

Download Full-text

Parameterization of Soil Hydraulic Parameters for HYDRUS-3D Simulation of Soil Water Dynamics in a Drip-Irrigated Orchard

Water ◽

10.3390/w12071858 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1858 ◽

Cited By ~ 1

Author(s):

Jesús María Domínguez-Niño ◽

Gerard Arbat ◽

Iael Raij-Hoffman ◽

Isaya Kisekka ◽

Joan Girona ◽

...

Keyword(s):

Soil Moisture ◽

Soil Water ◽

Drip Irrigation ◽

Water Dynamics ◽

Hydraulic Parameters ◽

Soil Water Dynamics ◽

Heterogeneous Distribution ◽

Neutron Probe ◽

Soil Hydraulic Parameters ◽

Soil Hydraulic

Although surface drip irrigation allows an efficient use of water in agriculture, the heterogeneous distribution of soil water complicates its optimal usage. Mathematical models can be used to simulate the dynamics of water in the soil below a dripper and promote: a better understanding, and optimization, of the design of drip irrigation systems, their improved management and their monitoring with soil moisture sensors. The aim of this paper was to find the most appropriate configuration of HYDRUS-3D for simulating the soil water dynamics in a drip-irrigated orchard. Special emphasis was placed on the source of the soil hydraulic parameters. Simulations parameterized using the Rosetta approach were therefore compared with others parameterized using that of HYPROP + WP4C. The simulations were validated on a seasonal scale, against measurements made using a neutron probe, and on the time course of several days, against tensiometers. The results showed that the best agreement with soil moisture measurements was achieved with simulations parameterized from HYPROP + WP4C. It further improved when the shape parameter n was empirically calibrated from a subset of neutron probe measurements. The fit of the simulations with measurements was best at positions near the dripper and worsened at positions outside its wetting pattern and at depths of 80 cm or more.

Download Full-text

Diurnal soil water dynamics in the shallow vadose zone (field site of China University of Geosciences, China)

Environmental Geology ◽

10.1007/s00254-008-1485-8 ◽

2008 ◽

Vol 58 (1) ◽

pp. 11-23 ◽

Cited By ~ 43

Author(s):

Yijian Zeng ◽

Li Wan ◽

Zhongbo Su ◽

Hirotaka Saito ◽

Kangle Huang ◽

...

Keyword(s):

Soil Water ◽

Vadose Zone ◽

Water Dynamics ◽

Field Site ◽

Soil Water Dynamics ◽

Zone Field

Download Full-text

Quantitative high-resolution observations of soil water dynamics in a complicated architecture with time-lapse Ground-Penetrating Radar

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-11-12365-2014 ◽

2014 ◽

Vol 11 (11) ◽

pp. 12365-12404

Author(s):

P. Klenk ◽

S. Jaumann ◽

K. Roth

Keyword(s):

High Resolution ◽

Water Content ◽

Soil Water ◽

Ground Penetrating Radar ◽

Time Lapse ◽

Test Site ◽

Water Dynamics ◽

Soil Water Dynamics ◽

Capillary Fringe ◽

Ground Penetrating

Abstract. High-resolution time-lapse Ground-Penetrating Radar (GPR) observations of advancing and retreating water tables can yield a wealth of information about near-surface water content dynamics. In this study, we present and analyze a series of imbibition, drainage and infiltration experiments which have been carried out at our artificial ASSESS test site and observed with surface based GPR. The test site features a complicated but known subsurface architecture constructed with three different kinds of sand. It allows studying soil water dynamics with GPR under a wide range of different conditions. Here, we assess in particular (i) the accurate determination of soil water dynamics averaged over the whole vertical extent by evaluating the bottom reflection and (ii) the feasibility of monitoring the dynamic shape of the capillary fringe reflection. The phenomenology of the GPR response of a dynamically changing capillary fringe is developed from a soil physical point of view. We then explain experimentally observed phenomena based on numerical simulations of both the water content dynamics and the expected GPR response.

Download Full-text

A particle based model for soil water dynamics: how to match and step beyond Richards' equation?

10.5194/hess-2016-107 ◽

2016 ◽

Author(s):

E. Zehe ◽

C. Jackisch

Keyword(s):

Soil Moisture ◽

Random Walk ◽

Soil Water ◽

Drift Velocity ◽

Maximum Velocity ◽

Water Dynamics ◽

Richards Equation ◽

Particle Model ◽

Soil Water Dynamics ◽

Non Linear

Abstract. Within this study we propose a stochastic approach to simulate soil water dynamics in the unsaturated zone by using a non-linear, space domain random walk of water particles. Soil water is represented by particles of constant mass, which travel according to the Itô form of the Fokker Planck equation. The model concept builds on established soil physics by estimating the drift velocity and the diffusion term based on the soil water characteristics. A naive random walk, which assumes all water particles to move at the same drift velocity and diffusivity, overestimated depletion of soil moisture gradients compared to a Richards' solver. This is because soil water and hence the corresponding water particles in smaller pore size fractions, are, due to the non-linear decrease of soil hydraulic conductivity with decreasing soil moisture, much less mobile. After accounting for this subscale variability of particle mobility, the particle model and a Richards' solver performed similarly during simulated wetting and drying circles in three distinctly different soils. The particle model typically produced slightly smaller top soil water contents during wetting and was faster in depleting soil moisture gradients during subsequent drainage phases. Within a real world benchmark the particle model matched observed soil moisture response to a moderated rainfall event even slightly better than the Richards' solver. The proposed approach is hence a promising, easy to implement alternative to the Richards equation. This is particularly also because it allows one to step beyond the assumption of local equilibrium during rainfall driven conditions. This is demonstrated by treating infiltrating event water particles as different type of particle which travel initially, mainly gravity driven, in the largest pore fraction at maximum velocity, and yet experience a slow diffusive mixing with the pre-event water particles within a characteristic mixing time.

Download Full-text

A Lagrangian model for soil water dynamics during rainfall-driven conditions

Hydrology and Earth System Sciences ◽

10.5194/hess-20-3511-2016 ◽

2016 ◽

Vol 20 (9) ◽

pp. 3511-3526 ◽

Cited By ~ 11

Author(s):

Erwin Zehe ◽

Conrad Jackisch

Keyword(s):

Soil Moisture ◽

Random Walk ◽

Soil Water ◽

Drift Velocity ◽

Water Dynamics ◽

Richards Equation ◽

Particle Model ◽

Soil Water Dynamics ◽

Non Linear ◽

Non Equilibrium

Abstract. Within this study we propose a stochastic approach to simulate soil water dynamics in the unsaturated zone by using a non-linear, space domain random walk of water particles. Soil water is represented by particles of constant mass, which travel according to the Itô form of the Fokker–Planck equation. The model concept builds on established soil physics by estimating the drift velocity and the diffusion term based on the soil water characteristics. A naive random walk, which assumes all water particles to move at the same drift velocity and diffusivity, overestimated depletion of soil moisture gradients compared to a Richards solver. This is because soil water and hence the corresponding water particles in smaller pore size fractions are, due to the non-linear decrease in soil hydraulic conductivity with decreasing soil moisture, much less mobile. After accounting for this subscale variability in particle mobility, the particle model and a Richards solver performed highly similarly during simulated wetting and drying circles in three distinctly different soils. Both models were in very good accordance during rainfall-driven conditions, regardless of the intensity and type of the rainfall forcing and the shape of the initial state. Within subsequent drying cycles the particle model was typically slightly slower in depleting soil moisture gradients than the Richards model. Within a real-world benchmark, the particle model and the Richards solver showed the same deficiencies in matching observed reactions of topsoil moisture to a natural rainfall event. The particle model performance, however, clearly improved after a straightforward implementation of rapid non-equilibrium infiltration, which treats event water as different types of particles, which travel initially in the largest pore fraction at maximum velocity and experience a slow diffusive mixing with the pre-event water particles. The proposed Lagrangian approach is hence a promising, easy-to-implement alternative to the Richards equation for simulating rainfall-driven soil moisture dynamics, which offers straightforward opportunities to account for preferential, non-equilibrium flow.

Download Full-text