scholarly journals Functional test of pedotransfer functions to predict water flow and solute transport with the dual-permeability model MACRO

2012 ◽  
Vol 9 (2) ◽  
pp. 2245-2282 ◽  
Author(s):  
J. Moeys ◽  
M. Larsbo ◽  
L. Bergström ◽  
C. D. Brown ◽  
Y. Coquet ◽  
...  
Keyword(s):  
Solute Transport ◽  
Water Flow ◽  
Preferential Flow ◽  
General Pattern ◽  
Regional Scale ◽  
Model Parameters ◽  
Model Efficiency ◽  
Fate Model ◽  
Solute Leaching ◽  
Pesticide Leaching

Abstract. Estimating pesticide leaching risks at the regional scale requires the ability to completely parameterise a pesticide fate model using only survey data, such as soil and land-use maps. Such parameterisation usually rely on a set of lookup tables and (pedo)transfer functions, relating elementary soil and site properties to model parameters. The aim of this paper is to describe and test a complete set of parameter estimation algorithms developed for the pesticide fate model MACRO, which accounts for preferential flow in soil macropores. We used tracer monitoring data from 16 lysimeter studies, carried out in three European countries, to evaluate the ability of MACRO and this "blind parameterisation" scheme to reproduce measured solute leaching at the base of each lysimeter. We focused on the prediction of early tracer breakthrough due to preferential flow, because this is critical for pesticide leaching. We then calibrated a selected number of parameters in order to assess to what extent the prediction of water and solute leaching could be improved. Our results show that water flow was generally reasonably well predicted (median model efficiency, ME, of 0.42). Although the general pattern of solute leaching was reproduced well by the model, the overall model efficiency was low (median ME = −0.26) due to errors in the timing and magnitude of some peaks. Preferential solute leaching at early pore volumes was also systematically underestimated. Nonetheless, the ranking of soils according to solute loads at early pore volumes was reasonably well estimated (concordance correlation coefficient, CCC, between 0.54 and 0.72). Moreover, we also found that ignoring macropore flow leads to a significant deterioration in the ability of the model to reproduce the observed leaching pattern, and especially the early breakthrough in some soils. Finally, the calibration procedure showed that improving the estimation of solute transport parameters is probably more important than the estimation of water flow parameters. Overall, the results are encouraging for the use of this modelling set-up to estimate pesticide leaching risks at the regional-scale, especially where the objective is to identify vulnerable soils and "source" areas of contamination.

scholarly journals Functional test of pedotransfer functions to predict water flow and solute transport with the dual-permeability model MACRO

2012 ◽  
Vol 16 (7) ◽  
pp. 2069-2083 ◽  
Author(s):  
J. Moeys ◽  
M. Larsbo ◽  
L. Bergström ◽  
C. D. Brown ◽  
Y. Coquet ◽  
...  
Keyword(s):  
Solute Transport ◽  
Water Flow ◽  
Preferential Flow ◽  
General Pattern ◽  
Regional Scale ◽  
Model Parameters ◽  
Model Efficiency ◽  
Fate Model ◽  
Solute Leaching ◽  
Pesticide Leaching

Abstract. Estimating pesticide leaching risks at the regional scale requires the ability to completely parameterise a pesticide fate model using only survey data, such as soil and land-use maps. Such parameterisations usually rely on a set of lookup tables and (pedo)transfer functions, relating elementary soil and site properties to model parameters. The aim of this paper is to describe and test a complete set of parameter estimation algorithms developed for the pesticide fate model MACRO, which accounts for preferential flow in soil macropores. We used tracer monitoring data from 16 lysimeter studies, carried out in three European countries, to evaluate the ability of MACRO and this "blind parameterisation" scheme to reproduce measured solute leaching at the base of each lysimeter. We focused on the prediction of early tracer breakthrough due to preferential flow, because this is critical for pesticide leaching. We then calibrated a selected number of parameters in order to assess to what extent the prediction of water and solute leaching could be improved. Our results show that water flow was generally reasonably well predicted (median model efficiency, ME, of 0.42). Although the general pattern of solute leaching was reproduced well by the model, the overall model efficiency was low (median ME = −0.26) due to errors in the timing and magnitude of some peaks. Preferential solute leaching at early pore volumes was also systematically underestimated. Nonetheless, the ranking of soils according to solute loads at early pore volumes was reasonably well estimated (concordance correlation coefficient, CCC, between 0.54 and 0.72). Moreover, we also found that ignoring macropore flow leads to a significant deterioration in the ability of the model to reproduce the observed leaching pattern, and especially the early breakthrough in some soils. Finally, the calibration procedure showed that improving the estimation of solute transport parameters is probably more important than the estimation of water flow parameters. Overall, the results are encouraging for the use of this modelling set-up to estimate pesticide leaching risks at the regional-scale, especially where the objective is to identify vulnerable soils and "source" areas of contamination.

Simulation of water and solute transport with MACRO model in Cecil loamy sand soil

Soil Research ◽  
2004 ◽  
Vol 42 (8) ◽  
pp. 939 ◽  
Author(s):  
Hasan Merdun ◽  
Virgil L. Quisenberry
Keyword(s):  
Solute Transport ◽  
Water Flow ◽  
Preferential Flow ◽  
Effective Diffusion ◽  
Loamy Sand ◽  
Model Parameters ◽  
Drainage Flow ◽  
Sand Soil ◽  
Flow And Transport ◽  
Loamy Sand Soil

Modelling preferential flow increases understanding of flow and transport processes in the unsaturated (vadose) zone and, hence, helps prevention of groundwater contamination. A dual-porosity model, MACRO, was evaluated for long-term drainage flow and short-term chloride-tagged water flow simulations in well-structured Cecil loamy sand soil. Water flow in micropores is calculated by the Richards’ equation, and simple gravity flow is assumed in the macropores. Solute transport in the micropores is calculated by the convection–dispersion equation (CDE), and the dispersion and diffusion in the CDE is neglected for the solute transport in the macropores. Based on the statistical criteria, the model accurately simulated drainage flow with depth and time. The average values of 3 statistical parameters (coefficient of residual mass, model efficiency, correlation coefficient) for drainage flow of different plots and times were 0.0057, 0.972, and 0.987, respectively. Similarly, the average values of the 3 statistical parameters in the same order for water flow and chloride transport of 4 plots were 0.097, 0.628, and 0.915, and 0.167, 0.938, and 0.982, respectively. The model simulated long-term drainage flow better than the short-term applied chloride-tagged water. The percentage recovery of measured water and chloride 2 h after the application ceased was 83 and 63 in the 1.05-m-deep profile of plot 1. This was a strong indication of preferential flow in this soil. Two-domain flow concept was required for acceptable simulation of this type of flow. In the 2-domain flow, boundary tension, boundary hydraulic conductivity, and effective diffusion path-length were the 3 most important parameters controlling flow and transport between the 2 domains. The effective diffusion path-length represented the structural development with depth in Cecil loamy sand soil. The relationships between the variability in flow and transport characteristics and fundamental soil properties and, hence, the associated key model parameters suggest that pedotransfer functions can be developed for the estimation of dual-porosity model parameters that control preferential flow.

The Daisy agroecological system model: A physically based model for preferential water flow and solute transport in drained agricultural fields

2021 ◽  
Author(s):  
Efstathios Diamantopoulos ◽  
Maja Holbak ◽  
Per Abrahamsen
Keyword(s):  
Solute Transport ◽  
Water Flow ◽  
Preferential Flow ◽  
Column Experiment ◽  
Soil Matrix ◽  
Physically Based Model ◽  
Physically Based ◽  
Rapid Transport ◽  
Preferential Water

<p>Preferential water flow and solute transport in agricultural systems affects not only the quality of groundwater but also the quality of surface waters like streams and lakes. This is due to the rapid transport of agrochemicals, immediately after application, through subsurface drainpipes and surface water. Experimental evidence attributes this to the occurrence of continuously connected pathways, connecting the soil surface directly with the drainpipes. We developed a physically-based model describing preferential flow and transport in biopores and implemented it in the agroecological model Daisy. The model simulates the often observed rapid transport of chemicals from   the upper soil layers to the drainpipes or to deeper layers of the soil matrix. Based on field investigations, biopores with specific characteristics can be parameterized as classes with different vertical and horizontal distributions. The model was tested against experimental data from a column experiment with an artificial biopore and showed good results in simulating preferential flow dynamics. We illustrate the performance of the new approach, by conducting five simulations assuming a two-dimensional simulation domain with different biopore parametrizations, from none to several different classes. The simulation results agreed with experimental observations reported in the literature, indicating rapid transport from the soil to the drainpipes. Furthermore, the different biopore parametrizations resulted in distinctly different leaching patterns, raising the expectation that biopore properties could be estimated or constrained based on observed leaching data and direct measurements.</p>

Agricultural hillslope soil heterogeneity challenges: first experimental results from SUPREHILL critical zone observatory

2021 ◽  
Author(s):  
Vedran Krevh ◽  
Jasmina Defterdarović ◽  
Lana Filipović ◽  
Zoran Kovač ◽  
Steffen Beck-Broichsitter ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Soil Moisture ◽  
Solute Transport ◽  
Soil Water ◽  
Water Flow ◽  
Preferential Flow ◽  
Soil Heterogeneity ◽  
Local Scale ◽  
Soil Water Flow ◽  
Critical Zone Observatory

<p>SUPREHILL is a new (2020) and first Croatian critical zone observatory (CZO), focused on local scale agricultural e.g., vineyard hillslope processes. The experimental setup includes an extensive sensor-based network accompanied by weighing lysimeters and instruments for surface and subsurface hydrology measurement. The field measurements are supported by novel laboratory and numerical quantification methods for the determination of water flow and solute transport. This combined approach will allow the research team to accurately determine soil water balance components (soil water flow, preferential flow/transport pathways, surface runoff, evapotranspiration), the temporal origin of water in hillslope hydrology (isotopes), transport of agrochemicals, and to calibrate and validate numerical modeling procedures for describing and predicting soil water flow and solute transport. First results from sensors indicate increased soil moisture on the hilltop, which is supported by precipitation data from rain gauges and weighing lysimeters. The presence of a compacted soil horizon and compacted inter-row parts (due to trafficking) of the vineyard seems to be highly relevant in regulating water dynamics. Wick lysimeters confirm the sensor soil moisture data, while showing a significant difference in its repetitions which suggests a possibility of a preferential flow imposed by local scale soil heterogeneity. Measured values of surface and subsurface runoff suggest a crucial role of these processes in the hillslope hydrology, while slope and structure dynamics additionally influence soil hydraulic properties. We are confident that the CZO will give us new insights in the landscape heterogeneity and substantially increase our understanding regarding preferential flow and nonlinear solute transport, with results directly applicable in agricultural (sloped agricultural soil management) and environmental (soil and water) systems. Challenges remain in characterizing local scale soil heterogeneity, dynamic properties quantification and scaling issues for which we will rely on combining CZO focused measurements and numerical modeling after substantial data is collected.</p>

scholarly journals A comprehensive quasi-3-D model for regional-scale unsaturated–saturated water flow

2019 ◽  
Vol 23 (8) ◽  
pp. 3481-3502 ◽  
Author(s):  
Wei Mao ◽  
Yan Zhu ◽  
Heng Dai ◽  
Ming Ye ◽  
Jinzhong Yang ◽  
...  
Keyword(s):  
Groundwater Recharge ◽  
Soil Water ◽  
Water Flow ◽  
Regional Scale ◽  
Coupled Model ◽  
Coupling Scheme ◽  
Model Parameters ◽  
Modeling Framework ◽  
Saturated Flow ◽  
D Model

Abstract. For computationally efficient modeling of unsaturated–saturated flow in regional scales, the quasi-three-dimensional (3-D) scheme that considers one-dimensional (1-D) soil water flow and 3-D groundwater flow is an alternative method. However, it is still practically challenging for regional-scale problems due to the highly nonlinear and intensive input data needed for soil water modeling and the reliability of the coupling scheme. This study developed a new quasi-3-D model coupled to the UBMOD 1-D soil water balance model with the MODFLOW 3-D hydrodynamic model. A new implementation method of the iterative scheme was developed in which the vertical net recharge and unsaturated zone depth were used as the exchange information. A modeling framework was developed to organize the coupling scheme of the soil water model and the groundwater model and to handle the pre- and post-processing information. The strength and weakness of the coupled model were evaluated by using two published studies. The comparison results show that the coupled model is satisfactory in terms of computational accuracy and mass balance error. The influences of spatial and temporal discretization as well as the stress period on the model accuracy were discussed. Additionally, the coupled model was used to evaluate groundwater recharge in a real-world study. The measured groundwater table and soil water content were used to calibrate the model parameters, and the groundwater recharge data from a 2-year tracer experiment were used to evaluate the recharge estimation. The field application further shows the practicability of the model. The developed model and the modeling framework provide a convenient and flexible tool for evaluating unsaturated–saturated flow systems at the regional scale.

scholarly journals Interplay between Fingering Instabilities and Initial Soil Moisture in Solute Transport through the Vadose Zone

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 917
Author(s):  
Luis Cueto-Felgueroso ◽  
María José Suarez-Navarro ◽  
Xiaojing Fu ◽  
Ruben Juanes
Keyword(s):  
Spatial Distribution ◽  
Solute Transport ◽  
Soil Water ◽  
Water Flow ◽  
Vadose Zone ◽  
Preferential Flow ◽  
Solute Diffusion ◽  
Wetting Front ◽  
Initial Soil ◽  
The Impact

Modeling water flow and solute transport in the vadose zone is essential to understanding the fate of soil pollutants and their travel times towards groundwater bodies. It also helps design better irrigation strategies to control solute concentrations and fluxes in semiarid and arid regions. Heterogeneity, soil texture and wetting front instabilities determine the flow patterns and solute transport mechanisms in dry soils. When water is already present in the soil, the flow of an infiltration pulse depends on the spatial distribution of soil water and on its mobility. We present numerical simulations of passive solute transport during unstable infiltration of water into sandy soils that are prone to wetting front instability. We study the impact of the initial soil state, in terms of spatial distribution of water content, on the infiltration of a solute-rich water pulse. We generate random fields of initial moisture content with spatial structure, through multigaussian fields with prescribed correlation lengths. We characterize the patterns of water flow and solute transport, as well as the mass fluxes through the soil column. Our results indicate a strong interplay between preferential flow and channeling due to fingering and the spatial distribution of soil water at the beginning of infiltration. Fingering and initial water saturation fields have a strong effect on solute diffusion and dilution into the ambient water during infiltration, suggesting an effective separation between mobile and inmobile transport domains that are controlled by the preferential flow paths due to fingering.

scholarly journals Predicting subsurface stormflow response of a forested hillslope – the role of connected flow paths

2014 ◽  
Vol 18 (1) ◽  
pp. 121-138 ◽  
Author(s):  
J. Wienhöfer ◽  
E. Zehe
Keyword(s):  
Solute Transport ◽  
Water Flow ◽  
Process Model ◽  
Preferential Flow ◽  
Quantitative Description ◽  
Lateral Flow ◽  
Hydrological Process ◽  
Flow Paths ◽  
Preferential Flow Paths ◽  
Model Set

Abstract. Rapid flow processes in connected preferential flow paths are widely accepted to play a key role in the rainfall–runoff response at the hillslope scale, but a quantitative description of these processes is still a major challenge in hydrological research. This paper investigates the approach of incorporating preferential flow paths explicitly in a process-based model for modelling water flow and solute transport at a steep forested hillslope. We conceptualise preferential flow paths as spatially explicit structures with high conductivity and low retention capacity, and evaluate simulations with different combinations of vertical and lateral flow paths in conjunction with variable or constant soil depths against measured discharge and tracer breakthrough. Out of 122 tested realisations, six set-ups fulfilled our selection criteria for the water flow simulation. These set-ups successfully simulated infiltration, vertical and lateral subsurface flow in structures, and allowed predicting the magnitude, dynamics and water balance of the hydrological response of the hillslope during successive periods of steady-state sprinkling on selected plots and intermittent rainfall on the entire hillslope area. The number of equifinal model set-ups was further reduced by the results of solute transport simulations. Two of the six acceptable model set-ups matched the shape of the observed breakthrough curve well, indicating that macrodispersion induced by preferential flow was captured well by the topology of the preferential flow network. The configurations of successful model set-ups suggest that preferential flow related to connected vertical and lateral flow paths is a first-order control on the hydrology of the study hillslope, whereas spatial variability of soil depth is secondary especially when lateral flow paths are present. Virtual experiments for investigating hillslope controls on subsurface processes should thus consider the effect of distinctive flow paths within the soil mantle. The explicit representation of flow paths in a hydrological process model was found to be a suitable approach for this purpose.

scholarly journals Simulating preferential soil water flow and tracer transport using the Lagrangian Soil Water and Solute Transport Model

2019 ◽  
Vol 23 (10) ◽  
pp. 4249-4267 ◽  
Author(s):  
Alexander Sternagel ◽  
Ralf Loritz ◽  
Wolfgang Wilcke ◽  
Erwin Zehe
Keyword(s):  
Solute Transport ◽  
Soil Water ◽  
Water Flow ◽  
Preferential Flow ◽  
Tracer Transport ◽  
Model Concept ◽  
Soil Matrix ◽  
Matrix Domain ◽  
Flow Domain ◽  
Water And Solute Transport

Abstract. We propose an alternative model concept to represent rainfall-driven soil water dynamics and especially preferential water flow and solute transport in the vadose zone. Our LAST-Model (Lagrangian Soil Water and Solute Transport) is based on a Lagrangian perspective of the movement of water particles (Zehe and Jackisch, 2016) carrying a solute mass through the subsurface which is separated into a soil matrix domain and a preferential flow domain. The preferential flow domain relies on observable field data like the average number of macropores of a given diameter, their hydraulic properties and their vertical length distribution. These data may be derived either from field observations or by inverse modelling using tracer data. Parameterization of the soil matrix domain requires soil hydraulic functions which determine the parameters of the water particle movement and particularly the distribution of flow velocities in different pore sizes. Infiltration into the matrix and the macropores depends on their respective moisture state, and subsequently macropores are gradually filled. Macropores and matrix interact through diffusive mixing of water and solutes between the two flow domains, which again depends on their water content and matric potential at the considered depths. The LAST-Model is evaluated using tracer profiles and macropore data obtained at four different study sites in the Weiherbach catchment in southern Germany and additionally compared against simulations using HYDRUS 1-D as a benchmark model. While both models show qual performance at two matrix-flow-dominated sites, simulations with LAST are in better accordance with the fingerprints of preferential flow at the two other sites compared to HYDRUS 1-D. These findings generally corroborate the feasibility of the model concept and particularly the implemented representation of macropore flow and macropore–matrix exchange. We thus conclude that the LAST-Model approach provides a useful and alternative framework for (a) simulating rainfall-driven soil water and solute dynamics and fingerprints of preferential flow as well as (b) linking model approaches and field experiments. We also suggest that the Lagrangian perspective offers promising opportunities to quantify water ages and to evaluate travel and residence times of water and solutes by a simple age tagging of particles entering and leaving the model domain.

scholarly journals Simulating preferential soil water flow and tracer transport using the Lagrangian Soil Water and Solute Transport Model

2019 ◽  
Author(s):  
Alexander Sternagel ◽  
Ralf Loritz ◽  
Wolfgang Wilcke ◽  
Erwin Zehe
Keyword(s):  
Solute Transport ◽  
Soil Water ◽  
Water Flow ◽  
Field Experiments ◽  
Preferential Flow ◽  
Sensitivity Analyses ◽  
Tracer Transport ◽  
Soil Matrix ◽  
Soil Water Flow ◽  
Water And Solute Transport

Abstract. We propose an alternative model to overcome these weaknesses of the Darcy-Richards approach and to simulate preferential soil water flow and tracer transport in macroporous soils. Our LAST-Model (Lagrangian Soil Water and Solute Transport) relies on a Lagrangian perspective on the movement of water particles carrying a solute mass through the soil matrix and macropores. We advance the model of Zehe and Jackisch (2016) by two main extensions: a) a new routine for solute transport within the soil matrix and b) the implementation of an additional 1-D preferential flow domain which simulates flow and transport in a population of macropores. Infiltration into the matrix and the macropores depends on their moisture state and subsequently macropores are gradually filled. Macropores and matrix interact through diffusive mixing of water and solutes between the two domains which depends on their water content and matric potential at the considered depths. The LAST-Model is then evaluated with sensitivity analyses and tested against tracer field experiments at three different sites. The results show the internal and physical validity of the model and the robustness of our solute transport and the linear mixing approach. Further, the model is able to simulate preferential flow through macropores and to depict well the observed 1-D solute mass profile of a tracer experiment with a high computational efficiency and short simulation times.

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