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>

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.

A Spectrum of Preferential Flow Alters Solute Mobility in the Critical Zone

2021 ◽  
Author(s):  
Jesse Radolinski ◽  
Hanh Le ◽  
Sheldon S. Hilaire ◽  
Kang Xia ◽  
Durelle Scott ◽  
...  
Keyword(s):  
Solute Transport ◽  
Water Flow ◽  
Organic Contaminants ◽  
Preferential Flow ◽  
Transport Theory ◽  
Transport Models ◽  
Soil Matrix ◽  
Solute Interactions ◽  
Fundamental Insight ◽  
Field Plots

Abstract Preferential flow reduces water residence times and allows rapid transport of pollutants such as organic contaminants. Conventional understanding of solute transport implies that preferential flow reduces the influence of soil matrix-solute interactions; however, this assumption lacks robust validation in the field. To better understand how physicochemical properties affect solute transport across a range of preferential flow conditions, we applied deuterium-labeled rainfall to field plots containing manure spiked with eight common antibiotics with a range of affinity for the soil. We then quantified preferential flow and solute transport using 48 soil pore water samplers spread along a hillslope. Based on >700 measurements, our data showed that solute transport to lysimeters was similar – regardless of antibiotic affinity for soil – when preferential flow represented less than 15% of the total water flow. When preferential flow exceeded 15%, however, concentrations were higher for compounds with relatively low affinity for soil. These results suggest that bypassing water flow can select for compounds that are more easily released from the soil matrix, thus providing fundamental insight into how flow heterogeneity affects pollutant mobility in soils. Moreover, because these data do not fully align with existing solute transport theory, they may be useful for building improved process-based transport models.

Simulating preferential soil water flow and reactive solute transport using the Lagrangian Soil Water and Solute Transport Model (LAST)

2020 ◽  
Author(s):  
Alexander Sternagel ◽  
Ralf Loritz ◽  
Wolfgang Wilcke ◽  
Erwin Zehe
Keyword(s):  
Solute Transport ◽  
Soil Water ◽  
Water Flow ◽  
Preferential Flow ◽  
Transport Model ◽  
Water Dynamics ◽  
Model Concept ◽  
Soil Matrix ◽  
Reactive Solute Transport ◽  
Water And Solute Transport

<p>Recently, we proposed 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 is based on a Lagrangian perspective on the movement of water particles (Zehe and Jackisch, 2016) carrying solute masses through the subsurface which is separated into a soil matrix domain and a preferential flow domain (Sternagel et al., 2019). 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 either be derived 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 pores 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.</p><p>The LAST-Model was evaluated using tracer profiles and macropore data obtained at four different study sites in the Weiherbach catchment in south Germany and additionally compared against simulations using HYDRUS 1-D as benchmark model. The results generally corroborated the feasibility of the model concept and particularly the implemented representation of macropore flow and macropore-matrix exchange. We thus concluded that the LAST-Model approach provides a useful and alternative framework for simulating rainfall-driven soil water and solute dynamics and fingerprints of preferential flow.</p><p>This study presents an extension of the model allowing for the simulation of reactive solute transport. Transformation kinetics are considered by transferring mass from the parent to the child components in each water particle according to the corresponding reaction rates, which is limited by the compound solubility. A retardation coefficient is not helpful in the particle-based framework, as the solute mass is carried by the water particles and travels thus by default at the same velocity. Ad- and desorption are explicit represented through transfer of dissolved mass from the water particles at a given depth to surrounding adsorption sites of the soil solid phase and vice versa. This may either operate under rate-limited or non-limited conditions. Adsorbed solute masses will be considered to be degraded following first-order reaction kinetics. The retardation process delays the solute displacement and enables a suitable time scale for the degradation process, which must be smaller than the time scale for the re-mobilization of the solutes. The proposed extension will be benchmarked against observations of pesticide transport in soil profiles and at tile-drained field sites.</p><p> </p><p>Zehe, E., Jackisch, C.: A Lagrangian model for soil water dynamics during rainfall-driven conditions, Hydrol. Earth Syst. Sci., 20, 3511–3526, https://doi.org/10.5194/hess-20-3511-2016, 2016.</p><p> </p><p>Sternagel, A., Loritz, R., Wilcke, W., and Zehe, E.: Simulating preferential soil water flow and tracer transport using the Lagrangian Soil Water and Solute Transport Model, Hydrol. Earth Syst. Sci., 23, 4249–4267, https://doi.org/10.5194/hess-23-4249-2019, 2019.</p>

scholarly journals Dye staining and excavation of a lateral preferential flow network

2009 ◽  
Vol 13 (6) ◽  
pp. 935-944 ◽  
Author(s):  
A. E. Anderson ◽  
M. Weiler ◽  
Y. Alila ◽  
R. O. Hudson
Keyword(s):  
Slope Stability ◽  
Solute Transport ◽  
Preferential Flow ◽  
Runoff Generation ◽  
Flow Paths ◽  
Soil Matrix ◽  
Preferential Flow Paths ◽  
Dye Staining ◽  
Hillslope Scale ◽  
Surrounding Soil

Abstract. Preferential flow paths have been found to be important for runoff generation, solute transport, and slope stability in many areas around the world. Although many studies have identified the particular characteristics of individual features and measured the runoff generation and solute transport within hillslopes, very few studies have determined how individual features are hydraulically connected at a hillslope scale. In this study, we used dye staining and excavation to determine the morphology and spatial pattern of a preferential flow network over a large scale (30 m). We explore the feasibility of extending small-scale dye staining techniques to the hillslope scale. We determine the lateral preferential flow paths that are active during the steady-state flow conditions and their interaction with the surrounding soil matrix. We also calculate the velocities of the flow through each cross-section of the hillslope and compare them to hillslope scale applied tracer measurements. Finally, we investigate the relationship between the contributing area and the characteristics of the preferential flow paths. The experiment revealed that larger contributing areas coincided with highly developed and hydraulically connected preferential flow paths that had flow with little interaction with the surrounding soil matrix. We found evidence of subsurface erosion and deposition of soil and organic material laterally and vertically within the soil. These results are important because they add to the understanding of the runoff generation, solute transport, and slope stability of preferential flow-dominated hillslopes.

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 Quantify Piston and Preferential Water Flow in Deep Soil Using Cl− and Soil Water Profiles in Deforested Apple Orchards on the Loess Plateau, China

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2183 ◽  
Author(s):  
Zhiqiang Zhang ◽  
Bingcheng Si ◽  
Huijie Li ◽  
Min Li
Keyword(s):  
Soil Water ◽  
Water Flow ◽  
Loess Plateau ◽  
Preferential Flow ◽  
Chloride Ions ◽  
Apple Orchards ◽  
The Loess Plateau ◽  
Deep Soil ◽  
Soil Water Profiles ◽  
Preferential Water

Piston and preferential water flow are viewed as the two dominant water transport mechanisms regulating terrestrial water and solute cycles. However, it is difficult to accurately separate the two water flow patterns because preferential flow is not easy to capture directly in field environments. In this study, we take advantage of the afforestation induced desiccated deep soil, and directly quantify piston and preferential water flow using chloride ions (Cl−) and soil water profiles, in four deforested apple orchards on the Loess Plateau. The deforestation time ranged from 3 to 15 years. In each of the four selected orchards, there was a standing orchard that was planted at the same time as the deforested one, and therefore the standing orchard was used to benchmark the initial Cl− and soil water profiles of the deforested orchard. In the deforested orchards, piston flow was detected using the migration of the Cl− front, and preferential flow was measured via soil water increase below the Cl− front. Results showed that in the desiccated zone, Cl− migrated to deeper soil after deforestation, indicating that the desiccated soil layer formed by the water absorption of deep-rooted apple trees did not completely inhibit the movement of water. Moreover, there was an evident increase in soil water below the downward Cl− front, directly demonstrating the existence of preferential flow in deep soil under field conditions. Although pore water velocity was small in the deep loess, preferential water flow still accounted for 34–65% of total infiltrated water. This study presented the mechanisms that regulate movement of soil water following deforestation through field observations and advanced our understanding of the soil hydrologic process in deep soil.

scholarly journals Development of physically based liquid water schemes for Greenland firn-densification models

2019 ◽  
Vol 13 (7) ◽  
pp. 1819-1842 ◽  
Author(s):  
Vincent Verjans ◽  
Amber A. Leeson ◽  
C. Max Stevens ◽  
Michael MacFerrin ◽  
Brice Noël ◽  
...  
Keyword(s):  
Water Flow ◽  
Liquid Water ◽  
Preferential Flow ◽  
Greenland Ice Sheet ◽  
Single Domain ◽  
Richards Equation ◽  
Retention Capacity ◽  
Water Percolation ◽  
Physically Based ◽  
Dual Domain

Abstract. As surface melt is increasing on the Greenland Ice Sheet (GrIS), quantifying the retention capacity of the firn layer is critical to linking meltwater production to meltwater runoff. Firn-densification models have so far relied on empirical approaches to account for the percolation–refreezing process, and more physically based representations of liquid water flow might bring improvements to model performance. Here we implement three types of water percolation schemes into the Community Firn Model: the bucket approach, the Richards equation in a single domain and the Richards equation in a dual domain, which accounts for partitioning between matrix and fast preferential flow. We investigate their impact on firn densification at four locations on the GrIS and compare model results with observations. We find that for all of the flow schemes, significant discrepancies remain with respect to observed firn density, particularly the density variability in depth, and that inter-model differences are large (porosity of the upper 15 m firn varies by up to 47 %). The simple bucket scheme is as efficient in replicating observed density profiles as the single-domain Richards equation, and the most physically detailed dual-domain scheme does not necessarily reach best agreement with observed data. However, we find that the implementation of preferential flow simulates ice-layer formation more reliably and allows for deeper percolation. We also find that the firn model is more sensitive to the choice of densification scheme than to the choice of water percolation scheme. The disagreements with observations and the spread in model results demonstrate that progress towards an accurate description of water flow in firn is necessary. The numerous uncertainties about firn structure (e.g. grain size and shape, presence of ice layers) and about its hydraulic properties, as well as the one-dimensionality of firn models, render the implementation of physically based percolation schemes difficult. Additionally, the performance of firn models is still affected by the various effects affecting the densification process such as microstructural effects, wet snow metamorphism and temperature sensitivity when meltwater is present.

Simulated Preferential Water Flow and Solute Transport in Shrinking Soils

2015 ◽  
Vol 14 (9) ◽  
pp. vzj2015.02.0021 ◽  
Author(s):  
Antonio Coppola ◽  
Alessandro Comegna ◽  
Giovanna Dragonetti ◽  
Horst H. Gerke ◽  
Angelo Basile
Keyword(s):  
Solute Transport ◽  
Water Flow ◽  
Preferential Water
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