scholarly journals Modified Richards equation and its exact solutions for soil water dynamics on eroding hillslopes

2002 ◽  
Vol 38 (6) ◽  
pp. 8-1-8-6 ◽  
Author(s):  
Ninghu Su
Keyword(s):  
Exact Solutions ◽  
Soil Water ◽  
Water Dynamics ◽  
Richards Equation ◽  
Soil Water Dynamics

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

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.

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

2016 ◽  
Vol 20 (9) ◽  
pp. 3511-3526 ◽  
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.

scholarly journals Testing the EPIC Richards submodel for simulating soil water dynamics under different bottom boundary conditions

2021 ◽  
Author(s):  
Matteo Longo ◽  
Curtis Dinnen Jones ◽  
Roberto César Izaurralde ◽  
Miguel L. Cabrera ◽  
Nicola Dal Ferro ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Soil Water ◽  
Water Dynamics ◽  
Soil Water Dynamics ◽  
Bottom Boundary

Numerical routine for soil water dynamics from trickle irrigation

2020 ◽  
Vol 83 ◽  
pp. 371-385 ◽  
Author(s):  
Ángel del Vigo ◽  
Sergio Zubelzu ◽  
Luis Juana
Keyword(s):  
Soil Water ◽  
Water Dynamics ◽  
Trickle Irrigation ◽  
Soil Water Dynamics

scholarly journals Analysis of Soil Water Response to Grass Transpiration

2013 ◽  
Vol 1 (No. 3) ◽  
pp. 85-98
Author(s):  
Dohnal Michal ◽  
Dušek Jaromír ◽  
Vogel Tomáš ◽  
Herza Jiří
Keyword(s):  
Soil Water ◽  
Water Uptake ◽  
Preferential Flow ◽  
Water Movement ◽  
Control Volume ◽  
Water Pressure ◽  
Lower Boundary ◽  
Root Water Uptake ◽  
Water Dynamics ◽  
Soil Water Dynamics

This paper focuses on numerical modelling of soil water movement in response to the root water uptake that is driven by transpiration. The flow of water in a lysimeter, installed at a grass covered hillslope site in a small headwater catchment, is analysed by means of numerical simulation. The lysimeter system provides a well defined control volume with boundary fluxes measured and soil water pressure continuously monitored. The evapotranspiration intensity is estimated by the Penman-Monteith method and compared with the measured lysimeter soil water loss and the simulated root water uptake. Variably saturated flow of water in the lysimeter is simulated using one-dimensional dual-permeability model based on the numerical solution of the Richards’ equation. The availability of water for the root water uptake is determined by the evaluation of the plant water stress function, integrated in the soil water flow model. Different lower boundary conditions are tested to compare the soil water dynamics inside and outside the lysimeter. Special attention is paid to the possible influence of the preferential flow effects on the lysimeter soil water balance. The adopted modelling approach provides a useful and flexible framework for numerical analysis of soil water dynamics in response to the plant transpiration.

Monitoring and modelling soil water dynamics using electromagnetic conductivity imaging and the ensemble Kalman filter

Geoderma ◽  
2017 ◽  
Vol 285 ◽  
pp. 76-93 ◽  
Author(s):  
Jingyi Huang ◽  
Alex B. McBratney ◽  
Budiman Minasny ◽  
John Triantafilis
Keyword(s):  
Kalman Filter ◽  
Soil Water ◽  
Ensemble Kalman Filter ◽  
Water Dynamics ◽  
Soil Water Dynamics ◽  
Conductivity Imaging

SIMULATION OF SOIL WATER DYNAMICS IN LAYERED SOILS

Soil Science ◽  
1977 ◽  
Vol 123 (1) ◽  
pp. 54-62 ◽  
Author(s):  
D. HILLEL ◽  
H. TALPAZ
Keyword(s):  
Soil Water ◽  
Water Dynamics ◽  
Layered Soils ◽  
Soil Water Dynamics
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