Journal articles on the topic 'Macropore flow'
To see the other types of publications on this topic, follow the link: Macropore flow.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Macropore flow.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Yi, Jun, Ye Yang, Muxing Liu, Wei Hu, Shulan Lou, Hailin Zhang, and Dongyou Zhang. "Characterising macropores and preferential flow of mountainous forest soils with contrasting human disturbances." Soil Research 57, no. 6 (2019): 601. http://dx.doi.org/10.1071/sr18198.
Full textAbstract:
Preferential flow can develop in soil macropores, and macropores are sensitive to human disturbances. This study investigated soil macropore features and the main factors controlling preferential flow at four sites with different levels of human disturbance in a mountainous area in Central China. The level of human disturbance decreased with increasing elevation, with the lowest elevation areas covered with coniferous trees (LF) > middle mountain areas covered with tea gardens (TG) > middle mountain areas covered with deciduous trees and mixed shrubs (MF) > subalpine areas covered with evergreen coniferous trees (HF). At each site, the soil macropore structure at 0–20 cm soil depth was analysed using computed tomography scans (0.6 mm resolution) and Image J software. Preferential flow was determined by analysing the breakthrough curve (BTC) of nitrate. The macroporosity, surface area density, mean macropore size, macropore number density, length density and node density were all ranked in the order of HF ≥ MF ≥ TG = LF. Less disturbed sites had stronger evidence of preferential flow as shown by faster breakthrough, longer tails and greater asymmetry of the BTCs. There were significant (P < 0.05) positive influences of soil macropore properties on pore water velocity and the solute dispersion coefficient. The dispersivity parameter was mainly affected by the macropore equivalent hydraulic radius. This study showed that human disturbance in the mountain forest areas significantly decreased soil macropores by changing soil physical properties (e.g. bulk density, texture and soil organic matter content) and root distribution, thus increasing the risk of surface runoff and nutrient losses.
2
Larsbo, M., J. Koestel, and N. Jarvis. "Controls of macropore network characteristics on preferential solute transport." Hydrology and Earth System Sciences Discussions 11, no. 8 (August 12, 2014): 9551–88. http://dx.doi.org/10.5194/hessd-11-9551-2014.
Full textAbstract:
Abstract. In this study we examined the relationships between macropore network characteristics, hydraulic properties and state variables and measures of preferential transport in undisturbed columns sampled from four agricultural topsoils of contrasting texture and structure. Macropore network characteristics were computed from 3-dimensional X-ray tomography images of the soil pore system. Non-reactive solute transport experiments were carried out at five steady-state water flow rates from 2 to 12 mm h−1. The degree of preferential transport was evaluated by the normalised 5% solute arrival time and the apparent dispersivity calculated from the resulting breakthrough curves. Near-saturated hydraulic conductivities were measured on the same samples using a tension disk infiltrometer placed on top of the columns. Results showed that many of the macropore network characteristics were inter-correlated. For example, large macroporosities were associated with larger specific macropore surface areas and better local connectivity of the macropore network. Generally, an increased flow rate resulted in earlier solute breakthrough and a shifting of the peak concentration towards smaller drained volumes. Columns with smaller macroporosities, poorer local connectivity of the macropore network and smaller near-saturated hydraulic conductivities exhibited a greater degree of preferential transport. This can be explained by the fact that, with only two exceptions, global (i.e. sample-scale) continuity of the macropore network was still preserved at low macroporosities. Thus, for any given flow rate pores of larger diameter were actively conducting solute in soils of smaller near-saturated hydraulic conductivity. With less time for equilibration between the macropores and the surrounding matrix the transport became more preferential. Conversely, the large specific macropore surface area and well-connected macropore networks associated with columns with large macroporosities limit the degree of preferential transport because they increase the diffusive flux between macropores and the soil matrix and they increase the near-saturated hydraulic conductivity. The normalised 5% arrival times were most strongly related with the estimated hydraulic state variables (e.g. with the degree of saturation in the macropores R2 = 0.589), since these combine into one measure the effects of irrigation rate and the near-saturated hydraulic conductivity function, which in turn implicitly depends on the volume, size distribution, global continuity, local connectivity and tortuosity of the macropore network.
3
Tofteng, Charlotte, Søren Hansen, and Henry E. Jensen. "Film and Pulse Flow in Artificial Macropores." Hydrology Research 33, no. 4 (August 1, 2002): 263–74. http://dx.doi.org/10.2166/nh.2002.0007.
Full textAbstract:
It is generally recognized that macropore flow may occur in unsaturated soil and that this should be taken into account when modelling flow of water and solutes in soil. The objective of the present study was to examine the water pressure potential conditions at which macropore flow may occur and to elucidate the nature of macropore flow. A laboratory setup consisting of a sand column 20 cm in diameter and 20 cm high with outlet into a 50 cm long glass tube was used. The outlet characteristics of the glass tube was either free to the atmosphere or the glass tube terminated in gravel. The tube diameters used were 3, 4, and 6 mm while the water application rates used were 1.2, 2.2, 12, and 18.5 mm h −1. Experiments covering 26 combinations of tube diameter, water application rate and outlet characteristics were conducted. Water entered the macropores at a water pressure potential in the overlying sand more or less equivalent to the water entry pressure potential of the macropore according to capillary theory. The nature of flow in the macropore was for the tubes of 3 mm and 4 mm in diameter predominantly pulse flow while film flow was more likely to occur in the tube of 6 mm in diameter. During pulse flow events a pressure potential gradient was consistently created in the sand column, the pressure potential decreasing to -20 cm to -30 cm corresponding approximately to the air entry pressure potential of the sand. The pulse flow events occurred repeatedly during the infiltration as long as water application was continued. When film flow occurred after a pulse flow event, the film flow continued at a water pressure potential less than -20 cm in the sand close to the opening of the artificial macropore.
4
Larsbo, M., J. Koestel, and N. Jarvis. "Relations between macropore network characteristics and the degree of preferential solute transport." Hydrology and Earth System Sciences 18, no. 12 (December 16, 2014): 5255–69. http://dx.doi.org/10.5194/hess-18-5255-2014.
Full textAbstract:
Abstract. The characteristics of the soil macropore network determine the potential for fast transport of agrochemicals and contaminants through the soil. The objective of this study was to examine the relationships between macropore network characteristics, hydraulic properties and state variables and measures of preferential transport. Experiments were carried out under near-saturated conditions on undisturbed columns sampled from four agricultural topsoils of contrasting texture and structure. Macropore network characteristics were computed from 3-D X-ray tomography images of the soil pore system. Non-reactive solute transport experiments were carried out at five steady-state water flow rates from 2 to 12 mm h−1. The degree of preferential transport was evaluated by the normalised 5% solute arrival time and the apparent dispersivity calculated from the resulting breakthrough curves. Near-saturated hydraulic conductivities were measured on the same samples using a tension disc infiltrometer placed on top of the columns. Results showed that many of the macropore network characteristics were inter-correlated. For example, large macroporosities were associated with larger specific macropore surface areas and better local connectivity of the macropore network. Generally, an increased flow rate resulted in earlier solute breakthrough and a shifting of the arrival of peak concentration towards smaller drained volumes. Columns with smaller macroporosities, poorer local connectivity of the macropore network and smaller near-saturated hydraulic conductivities exhibited a greater degree of preferential transport. This can be explained by the fact that, with only two exceptions, global (i.e. sample scale) continuity of the macropore network was still preserved at low macroporosities. Thus, for any given flow rate, pores of larger diameter were actively conducting solute in soils of smaller near-saturated hydraulic conductivity. This was associated with larger local transport velocities and, hence, less time for equilibration between the macropores and the surrounding matrix which made the transport more preferential. Conversely, the large specific macropore surface area and well-connected macropore networks associated with columns with large macroporosities limit the degree of preferential transport because they increase the diffusive flux between macropores and the soil matrix and they increase the near-saturated hydraulic conductivity. The normalised 5% arrival times were most strongly correlated with the estimated hydraulic state variables (e.g. with the degree of saturation in the macropores R2 = 0.589), since these combine into one measure the effects of irrigation rate and the near-saturated hydraulic conductivity function, which in turn implicitly depends on the volume, size distribution, global continuity, local connectivity and tortuosity of the macropore network.
5
Jiang, Xiaojin, Enheng Wang, Xiangwei Chen, Xiangyou Xia, and Changting Shi. "Field study on macropore flow in typical Black soils of northeast China." Canadian Journal of Soil Science 92, no. 3 (March 2012): 559–66. http://dx.doi.org/10.4141/cjss2010-041.
Full textAbstract:
Jiang, X., Wang, E., Chen, X., Xia, X. and Shi, C. 2012. Field study on macropore flow in typical Black soils of northeast China. Can. J. Soil Sci. 92: 559–566. Macropores are important preferential pathways for the transport of water and contaminants in soil. A series of hood infiltration experiments were conducted using dye tracers (Brilliant Blue FCF) at pressure heads of −5.0 cm, −3.0 cm, and −1.0 cm at a conventional tilled site on Keshan Farm, northeast China. The study objective was to combine the test method of dye tracing with a hood infiltrometer to analyze soil subjected to conventional tillage methods. Dye staining patterns and macroporous networks were analyzed by excavation, mapping, photography, and image analysis. Results showed that macropore flow began very near the soil surface under three pressures heads of −5.0 cm, −3.0 cm and −1.0 cm, and that a pressure head of −1.0 cm resulted in more lateral flow. Soil deeper than 40.0 cm was less disturbed, which resulted in good continuity. At pressure heads of −5.0, −3.0 and −1.0 cm, the dye staining technique resulted in maximum stained depths of 74.3, 60.7 and 64.7 cm, respectively, with maximum stained widths of 41.6, 41.5 and 47.9 cm, respectively (at depths from 14.0 to 28.0 cm). Soil under a pressure head of −1.0 cm had the highest initial and steady infiltration rates of 13.0 and 4.1 mm min−1, respectively. Soil under a pressure head of −5.0 cm showed the most connectivity. To distinguish the macropores from the interaction area of macropore flow and the soil matrix surrounding the macropores, the stained area was separated into different classes based on dye color.
6
Bidwell, V. J., and H. R. Thorpe. "Kinematic cell model of macropore flow from intermittent irrigation pulses." Soil Research 39, no. 4 (2001): 837. http://dx.doi.org/10.1071/sr00070.
Full textAbstract:
Significant fluctuations in soil water flux were observed in the drainage hydrographs from lysimeters (1220 mm diam., 900 mm deep) of undisturbed field soil, recorded at 5-min intervals, in response to intermittent 1-min pulses of irrigation water (3.4 or 6.8 mm) at irregular time intervals (4–17 min). The hypothetical process for this phenomenon was flow through soil macropores, in association with non-linear sorption into soil micropores. The kinematic wave approach to analysing macropore flow was modelled as a series of bi-continuum cells, which can be expressed as a set of non-linear ordinary differential equations. This non-linear state-space description enables the use of MATLAB software for convenient coding of the model and numerical integration of the model response to transient water flux input. Model simulation of drainage response to the irrigation pulse sequences showed good prediction of the wetting and draining fronts of the hydrograph but gave only indicative prediction of the magnitudes and wavelengths of the flow fluctuations. The model demonstrates the sensitivity of macropore flow to variations in the intervals between irrigation pulses, and supports previous evidence of fluctuations in macropore flow even for single water flux input pulses under laboratory conditions.
7
Zhang, Youyan, Zhe Cao, Fang Hou, and Jinhua Cheng. "Characterizing Preferential Flow Paths in Texturally Similar Soils under Different Land Uses by Combining Drainage and Dye-Staining Methods." Water 13, no. 2 (January 18, 2021): 219. http://dx.doi.org/10.3390/w13020219.
Full textAbstract:
Preferential flow paths have been widely characterized by many visualization methods. However, the differences in preferential flow paths under various land uses and their relationships to hydraulic properties remain uncertain. The objectives of this study are to (1) characterize preferential flow paths under various land uses (forest and orchard) by combining drainage and dye-staining methods and to (2) build a connection between preferential flow paths and hydraulic-related parameters and extract the proportion of preferential flow paths from the compounding effects of matrix flow and preferential flow. The dye-staining experiments were conducted in five sandy soils and one sandy clay loam in situ, including four soils from forest and two soils from orchards. A total of 47 soil cores, 4 cm in height and 9 cm in diameter, were collected in each layer of the dye-stained soils for drainage experiments in the laboratory. Dye coverage and hydraulically equivalent macropore parameters (macroporosity, pore size distribution, and number of macropores) and their relationships were analyzed. The results show that the volume of preferential flow is partly affected by the total macropore volume. The effect of macropores on preferential flow varies by macropore size distribution. Dye coverage exhibited a significant (P < 0.01) correlation with macroporosity (correlation coefficient 0.83). Based on the value of macroporosity or steady effluent rates, the part of the dye coverage that was due to preferential flow on the surface dye-stained soil (resulting from both matrix and preferential flow) could be identified in this study. Compared with orchards, forestland has more preferential flow paths in both surface soil and subsoil. Further studies are needed to quantify the 3-D preferential flow paths and build a connection between preferential flow paths and hydraulic properties.
8
Naveed, Muhammad, Per Moldrup, Marcel G. Schaap, Markus Tuller, Ramaprasad Kulkarni, Hans-Jörg Vogel, and Lis Wollesen de Jonge. "Prediction of biopore- and matrix-dominated flow from X-ray CT-derived macropore network characteristics." Hydrology and Earth System Sciences 20, no. 10 (October 6, 2016): 4017–30. http://dx.doi.org/10.5194/hess-20-4017-2016.
Full textAbstract:
Abstract. Prediction and modeling of localized flow processes in macropores is of crucial importance for sustaining both soil and water quality. However, currently there are no reliable means to predict preferential flow due to its inherently large spatial variability. The aim of this study was to investigate the predictive performance of previously developed empirical models for both water and air flow and to explore the potential applicability of X-ray computed tomography (CT)-derived macropore network characteristics. For this purpose, 65 cylindrical soil columns (6 cm diameter and 3.5 cm height) were extracted from the topsoil (5 cm to 8.5 cm depth) in a 15 m × 15 m grid from an agricultural field located in Silstrup, Denmark. All soil columns were scanned with an industrial X-ray CT scanner (129 µm resolution) and later employed for measurement of saturated hydraulic conductivity, air permeability at −30 and −100 cm matric potential, and gas diffusivity at −30 and −100 cm matric potential. Distribution maps for saturated hydraulic conductivity, air permeability, and gas diffusivity reflected no autocorrelation irrespective of soil texture and organic matter content. Existing empirical predictive models for saturated hydraulic conductivity and air permeability showed poor performance, as they were not able to realistically capture macropore flow. The tested empirical model for gas diffusivity predicted measurements at −100 cm matric potential reasonably well, but failed at −30 cm matric potential, particularly for soil columns with biopore-dominated flow. X-ray CT-derived macroporosity matched the measured air-filled porosity at −30 cm matric potential well. Many of the CT-derived macropore network characteristics were strongly interrelated. Most of the macropore network characteristics were also significantly correlated with saturated hydraulic conductivity, air permeability, and gas diffusivity. The predictive Ahuja et al. (1984) model for saturated hydraulic conductivity, air permeability, and gas diffusivity performed reasonably well when parameterized with novel, X-ray CT-derived parameters such as effective percolating macroporosity for biopore-dominated flow and total macroporosity for matrix-dominated flow. The obtained results further indicate that it is crucially important to discern between matrix-dominated and biopore-dominated flow for accurate prediction of macropore flow from X-ray CT-derived macropore network characteristics.
9
Franssen, Jan, Catherine Blais, Michel Lapointe, Francis Bérubé, Normand Bergeron, and Pierre Magnan. "Asphyxiation and entombment mechanisms in fines rich spawning substrates: experimental evidence with brook trout (Salvelinus fontinalis) embryos." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 3 (March 2012): 587–99. http://dx.doi.org/10.1139/f2011-168.
Full textAbstract:
We investigated the distinct physical controls causing entombment and asphyxiation, the key mechanisms influencing salmonid egg-to-emergence (EtE) survival. Entombment occurs when sediment blocks the interstitial pathways (macropores) that larvae use to emerge from the streambed, while asphyxiation is related to low oxygen flux, which is a function of interstitial flow velocity. EtE survival has been related to substrate composition and flow velocity. However, in streambed sediments these variables are correlated, and few studies have examined the sensitivity of EtE survival to changes in velocity and oxygen flux at fixed substrate composition. EtE survival has not yet been directly related to the size and density of macropores. We incubated brook trout ( Salvelinus fontinalis ) embryos in artificial redds with different sediment compositions and hydraulic gradients to examine independently the effects of substrate composition, macropore geometry, and flow velocity on EtE survival, emergence timing, and fry condition. In situ measurements of macropore size were obtained using a computed tomography scanner. Despite high oxygen concentrations, we observed that entombment or blockage effects caused high embryo mortality in fines-rich substrates with few large macropores, and triggered early emergence of rare survivors. These outcomes could not be mitigated by increased flow velocity and oxygen flux to the egg pocket.
10
Sternagel, Alexander, Ralf Loritz, Wolfgang Wilcke, and Erwin Zehe. "Simulating preferential soil water flow and tracer transport using the Lagrangian Soil Water and Solute Transport Model." Hydrology and Earth System Sciences 23, no. 10 (October 22, 2019): 4249–67. http://dx.doi.org/10.5194/hess-23-4249-2019.
Full textAbstract:
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.
11
Radka, Kodešova, and Šimůnek Josef Kozak and Jiři. "Numerical Study of Macropore Impact on Ponded Infiltration in Clay Soils." Soil and Water Research 1, No. 1 (January 7, 2013): 16–22. http://dx.doi.org/10.17221/6501-swr.
Full textAbstract:
The single-porosity and dual-permeability models in HYDRUS-1D (Šimůnek et al. 1998, 2003) were used to simulate variably-saturated water movement in clay soils with and without macropores. Numerical simulations of water flow for several scenarios of probable macropore compositions show a considerable impact of preferential flow on water infiltration in such soils. Preferential flow must be considered to predict water recharge in clay soils.
12
Kördel, Werner, and Michael Klein. "Prediction of leaching and groundwater contamination by pesticides." Pure and Applied Chemistry 78, no. 5 (January 1, 2006): 1081–90. http://dx.doi.org/10.1351/pac200678051081.
Full textAbstract:
Herein, we describe how pesticide leaching is assessed in Europe in order to fulfill EU Directive 91/414. The assessment schemes were developed to protect groundwater from unacceptable effects caused by pesticide use. They presently focus on chromatographic flow processes, which are dominant in sandy soils. Nevertheless, important regions in Europe are characterized by structured soils where transport through macropores is most relevant.Comparison of parallel field studies with isoproturon performed in sandy and silty soils showed that maximum concentration in the structured soil at a soil depth of 1 m may exceed respective concentrations in sandy soils by a factor of 60. Similar results were obtained by lysimeter studies using silty soil cores with maximum concentration of 40 μg/l at the soil bottom. These results demonstrate that preferential flow is more the rule than the exception in well-structured fine-textured soils, and pesticide losses via macropore flow may exceed losses via matrix transport considerably. All present information available for macropore flow suggest the need for greater regional assessments. Other recommendations include analysis of the influence of different soil management practices on the formation of macropores.
13
Quinn, Ruth, and Alejandro Dussaillant. "The impact of macropores on heavy metal retention in sustainable drainage systems." Hydrology Research 49, no. 2 (February 19, 2018): 517–27. http://dx.doi.org/10.2166/nh.2018.277.
Full textAbstract:
Abstract Numerous laboratory and field experiments have found that rain gardens exhibit excellent heavy metal retention (>88%). However, none examined the impact of macropore flow on this retention; this was established to be a key factor in heavy metal capture by previous landfill leachate experiments. Therefore, the aim of the experiments detailed in this paper was to investigate the effect of a single artificial macropore on heavy metal retention in a layered soil column (with a similar configuration to a rain garden). The findings of these experiments suggest that macropore flow does not impact the hydraulic performance or heavy metal retention of the columns with 99% of copper, lead and zinc captured. This indicates that macropores are not detrimental to heavy metal retention in rain garden systems with highly conductive soils; this was attributed to the high hydraulic conductivity of the media used and the depth of the system. However, in shallower systems, such as green roofs, the retention of heavy metals and other pollutants may be impacted by the existence of preferential flow, and more research into this area is needed.
14
Kördel, Werner, Hans Egli, and Michael Klein. "Transport of pesticides via macropores (IUPAC Technical Report)." Pure and Applied Chemistry 80, no. 1 (January 1, 2008): 105–60. http://dx.doi.org/10.1351/pac200880010105.
Full textAbstract:
This report provides an overview of the transport of solutes via macropores focusing on the practical relevance of the phenomenon. After a description of matrix flow and preferential flow in soil, information related to macropores, including their formation and measurement techniques, is briefly presented. Then, the influence of experimental conditions and of environmental and agricultural factors and pesticide properties is discussed, based on a statistical evaluation of all published studies offering sufficient quantitative information. Most of the analyzed parameters do not significantly influence the experimental pesticide losses. The groundwater ubiquity score (GUS) index turned out to be the most important compound property to describe substance losses through macropore flow. In a third section, tools for modeling pesticide transport through macropores are presented and critically evaluated. Results of the computer model MACRO, which is also used in the EU pesticide registration process, are compared with experimental losses. For five out of seven investigated pesticides (A-D, F), the simulated losses are in agreement with the experimental data. However, for two compounds with very low KOC values, MACRO overestimated the losses. Finally, the significance of pesticide transport via macropores for contamination of ground and surface water is assessed. Losses caused by macropore transport may considerably exceed losses caused by matrix transport at a specific site. Therefore, a site-specific assessment of pesticide leaching is needed.
15
Zhang, Yifu, Ruihong Zhang, Baofeng Zhang, and Xiaobo Xi. "Artificial Macropores with Sandy Fillings Enhance Desalinization and Increase Plant Biomass in Two Contrasting Salt-Affected Soils." Applied Sciences 11, no. 7 (March 29, 2021): 3037. http://dx.doi.org/10.3390/app11073037.
Full textAbstract:
Salt accumulation in topsoil is a widespread restricting factor that limits agricultural production and threatens food security in arid and semi-arid regions. However, whether this upward enrichment was suppressed by macropores was less documented. Therefore, artificial macropores with sandy fillings (AMSF) method was proposed in this study. Soil column experiments showed a significant improvement of saturated hydraulic conductivity (Ks) by more than 260% under artificial macropore treatment. Freshwater irrigation was conducted to monitor the short-term water and salt movement. This research aimed at evaluating the potential benefit of AMSF method on soil desalinization in coastal farmland of northern China. The results demonstrated that downward movement of soil water was stimulated in AMSF method, accordingly, washing more salt ions out of top rooting zone. Particularly, 10 cm or more macropore depth treatments of AMSF method enhanced total desalinization by 52.1% to 176.6% in 0–30 cm soil layer, in comparison to the control group without macropore. Subsequent observations for alfalfa showed higher biomass by 20.8% under 15 cm macropore depth. The results here provided an exploration demonstration to pursue these studies with the ultimate goal of optimizing application strategies for amendment in coastal salt-affected lands of northern China.
16
Müller, Karin, Céline Duwig, Anne-Julie Tinet, Alfonso Gastelum Strozzi, Lorenzo Spadini, Marie Christine Morel, and Pascal Charrier. "Orchard management and preferential flow in Andosols – comparing two kiwifruit orchards in New Zealand." Soil Research 57, no. 6 (2019): 615. http://dx.doi.org/10.1071/sr18293.
Full textAbstract:
Sustainable horticulture depends on the integrity of soil functions, which directly depend on soil architecture affecting aggregation, root growth, as well as liquid and gas permeability. We hypothesised that changes in soil architecture resulting from feedback mechanisms between management, soil organic carbon contents (SOC), biota and vegetation can be captured with X-ray computed tomography (CT), and that these affect the soil filtering function, which thus, can be manipulated through orchard management. We compared the transport of copper, a widely used fungicide, through intact soil cores from vine rows of kiwifruit orchards under organic and integrated management. We first derived 3D-macropore characteristics from CT-images, followed by leaching a pulse of copper and a tracer through the same cores. The organic orchard soil had a significantly higher SOC content than the integrated orchard soil, and this was positively correlated with total porosity. Macropores (>92µm) were larger with a higher connectivity, but significantly fewer in the organic than the integrated orchard soil. This resulted in a lower macroporosity and a better copper filtering capacity of the organic than the integrated orchard soil. Copper distribution was reasonably predicted when combining SOC contents, pH and macropore characteristics. Significant relationships between soil parameters and indicators of the strength of preferential flow verified that CT-derived macropore characteristics can be used to predict functional solute transport parameters. The relevance of our results and relationships observed between macropore characteristics, functional indicators of preferential flow and the fate of copper needs verification with samples representing more soils and sites.
17
Naveed, M., P. Moldrup, M. Schaap, M. Tuller, R. Kulkarni, H. J. Vögel, and L. Wollesen de Jonge. "Macropore flow at the field scale: predictive performance of empirical models and X-ray CT analyzed macropore characteristics." Hydrology and Earth System Sciences Discussions 12, no. 11 (November 20, 2015): 12089–120. http://dx.doi.org/10.5194/hessd-12-12089-2015.
Full textAbstract:
Abstract. Predictions of macropore flow is important for maintaining both soil and water quality as it governs key related soil processes e.g. soil erosion and subsurface transport of pollutants. However, macropore flow currently cannot be reliably predicted at the field scale because of inherently large spatial variability. The aim of this study was to perform field scale characterization of macropore flow and investigate the predictive performance of (1) current empirical models for both water and air flow, and (2) X-ray CT derived macropore network characteristics. For this purpose, 65 cylindrical soil columns (6 cm diameter and 3.5 cm height) were extracted from the topsoil (5 to 8.5 cm depth) in a 15 m × 15 m grid from an agricultural loamy field located in Silstrup, Denmark. All soil columns were scanned with an industrial CT scanner (129 μm resolution) and later used for measurements of saturated water permeability, air permeability and gas diffusivity at −30 and −100 cm matric potentials. Distribution maps for both water and air permeabilities and gas diffusivity reflected no spatial correlation irrespective of the soil texture and organic matter maps. Empirical predictive models for both water and air permeabilities showed poor performance as they were not able to realistically capture macropore flow because of poor correlations with soil texture and bulk density. The tested empirical model predicted well gas diffusivity at −100 cm matric potential, but relatively failed at −30 cm matric potential particularly for samples with biopore flow. Image segmentation output of the four employed methods was nearly the same, and matched well with measured air-filled porosity at −30 cm matric potential. Many of the CT derived macropore network characteristics were strongly interrelated. Most of the macropore network characteristics were also strongly correlated with saturated water permeability, air permeability, and gas diffusivity. The correlations between macropore network characteristics and macropore flow parameters were further improved on dividing soil samples into samples with biopore and matrix flow. Observed strong correlations between macropore network characteristics and macropore flow highlighted the need of further research on numerical simulations of macropore flow based on X-ray CT images. This could pave the way for the digital soil physics laboratory in the future.
18
Liu, Mu Xing, Wen Hu Cui, Dan Wu, Li Juan Liao, and Wen Zheng Du. "Soil Macropore Structures and their Effect on Preferential Flow." Applied Mechanics and Materials 522-524 (February 2014): 990–94. http://dx.doi.org/10.4028/www.scientific.net/amm.522-524.990.
Full textAbstract:
Recent researches on soil macropore and preferential flow were reviewed in this paper. Definition of macropore, causes of preferential flow, observation technologies, and preferential simulated models were introduced. Soil macropore investigated methods include dye tracing, sectioning, CT scan, tension infiltration curve, and markers tracing. Preferential flow models include two domain model and multiple domain model, two phase model and hybrid model, etc.
19
Holden, Joseph. "Topographic controls upon soil macropore flow." Earth Surface Processes and Landforms 34, no. 3 (March 15, 2009): 345–51. http://dx.doi.org/10.1002/esp.1726.
Full text
20
Pelíšek, I. "Investigation of soil water infiltration at a scale of individual earthworm channels." Soil and Water Research 13, No. 1 (January 24, 2018): 1–10. http://dx.doi.org/10.17221/283/2014-swr.
Full textAbstract:
This study focused on the hydraulic efficiency of vertical earthworm channels (henceforth referred to as macropores or channels). The parameters selected for investigation were the rate of change in hydraulic soil conductivity in the channel walls due to compaction, the rate of this compaction, and the wall stability against running and stagnant water. We preferentially tested the variants for infiltration of water flowing from the soil horizons against gravity (e.g. from the level of installation of tile and controlled drainage). The details of influx and infiltration processes were examined both in the field and more thoroughly in the laboratory using an accurate continuous infiltrometer constructed at the Research Institute for Soil and Water Conservation (RISWC), Czech Republic. Both direct measurements and indirect evidence consisted of tests of individual natural macropores directly in the field, as well as tests of intact collected samples and artificial samples with variants of natural, artificially extruded, and cut out tubular macropores. We studied the processes occurring in macropores with diameters of ca. 5 mm and larger. In these particular conditions, we identified the apparent saturated hydraulic conductivity (K<sub>s</sub>') of the soil horizons (including macropore-mediated vertical surface infiltration and preferential flow to soil followed by radial infiltration) most frequent as K<sub>i</sub> (apparent saturated hydraulic conductivity affected by preferential flow or influx of water) from 50 to 200 cm/h. In some cases, saturated hydraulic conductivity of earthworm channel walls (K<sub>sw</sub>) was reduced in the order of tens of percent compared with matrix K<sub>s</sub>. The increase of bulk density of soil (ρ<sub>d</sub>) in the macropore vicinity reached the maximum of 25%. The intensity of macropore wall erosion (i<sub>er</sub>) ranged from 0 to 70 mg/min/dm<sup>2</sup>.
21
Roulier, Stéphanie, and Nicholas Jarvis. "Modeling Macropore Flow Effects on Pesticide Leaching." Journal of Environmental Quality 32, no. 6 (November 2003): 2341–53. http://dx.doi.org/10.2134/jeq2003.2341.
Full text
22
Ghodrati, Masoud, Michael Chendorain, and Y. Jason Chang. "Characterization of Macropore Flow Mechanisms in Soil by Means of a Split Macropore Column." Soil Science Society of America Journal 63, no. 5 (September 1999): 1093–101. http://dx.doi.org/10.2136/sssaj1999.6351093x.
Full text
23
Germer, K., and J. Braun. "Macropore-Matrix Water Flow Interaction around a Vertical Macropore Embedded in Fine Sand-Laboratory Investigations." Vadose Zone Journal 14, no. 7 (July 2015): vzj2014.03.0030. http://dx.doi.org/10.2136/vzj2014.03.0030.
Full text
24
Hardie, Marcus A., Richard B. Doyle, William E. Cotching, and Shaun Lisson. "Subsurface Lateral Flow in Texture-Contrast (Duplex) Soils and Catchments with Shallow Bedrock." Applied and Environmental Soil Science 2012 (2012): 1–10. http://dx.doi.org/10.1155/2012/861358.
Full textAbstract:
Development-perched watertables and subsurface lateral flows in texture-contrast soils (duplex) are commonly believed to occur as a consequence of the hydraulic discontinuity between the A and B soil horizons. However, in catchments containing shallow bedrock, subsurface lateral flows result from a combination of preferential flow from the soil surface to the soil—bedrock interface, undulations in the bedrock topography, lateral flow through macropore networks at the soil—bedrock interface, and the influence of antecedent soil moisture on macropore connectivity. Review of literature indicates that some of these processes may also be involved in the development of subsurface lateral flow in texture contrast soils. However, the extent to which these mechanisms can be applied to texture contrast soils requires further field studies. Improved process understanding is required for modelling subsurface lateral flows in order to improve the management of waterlogging, drainage, salinity, and offsite agrochemicals movement.
25
Weiler, Markus, and Felix Naef. "Simulating surface and subsurface initiation of macropore flow." Journal of Hydrology 273, no. 1-4 (March 2003): 139–54. http://dx.doi.org/10.1016/s0022-1694(02)00361-x.
Full text
26
Urbina, C. A. Faúndez, J. C. Dam, R. F. A. Hendriks, F. Berg, H. P. A. Gooren, and C. J. Ritsema. "Water Flow in Soils with Heterogeneous Macropore Geometries." Vadose Zone Journal 18, no. 1 (January 2019): 1–17. http://dx.doi.org/10.2136/vzj2019.02.0015.
Full text
27
Alaoui, Abdallah. "Modelling susceptibility of grassland soil to macropore flow." Journal of Hydrology 525 (June 2015): 536–46. http://dx.doi.org/10.1016/j.jhydrol.2015.04.016.
Full text
28
Sternagel, Alexander, Ralf Loritz, Julian Klaus, Brian Berkowitz, and Erwin Zehe. "Simulation of reactive solute transport in the critical zone: a Lagrangian model for transient flow and preferential transport." Hydrology and Earth System Sciences 25, no. 3 (March 25, 2021): 1483–508. http://dx.doi.org/10.5194/hess-25-1483-2021.
Full textAbstract:
Abstract. We present a method to simulate fluid flow with reactive solute transport in structured, partially saturated soils using a Lagrangian perspective. In this context, we extend the scope of the Lagrangian Soil Water and Solute Transport Model (LAST) (Sternagel et al., 2019) by implementing vertically variable, non-linear sorption and first-order degradation processes during transport of reactive substances through a partially saturated soil matrix and macropores. For sorption, we develop an explicit mass transfer approach based on Freundlich isotherms because the common method of using a retardation factor is not applicable in the particle-based approach of LAST. The reactive transport method is tested against data of plot- and field-scale irrigation experiments with the herbicides isoproturon and flufenacet at different flow conditions over various periods. Simulations with HYDRUS 1-D serve as an additional benchmark. At the plot scale, both models show equal performance at a matrix-flow-dominated site, but LAST better matches indicators of preferential flow at a macropore-flow-dominated site. Furthermore, LAST successfully simulates the effects of adsorption and degradation on the breakthrough behaviour of flufenacet with preferential leaching and remobilization. The results demonstrate the feasibility of the method to simulate reactive solute transport in a Lagrangian framework and highlight the advantage of the particle-based approach and the structural macropore domain to simulate solute transport as well as to cope with preferential bypassing of topsoil and subsequent re-infiltration into the subsoil matrix.
29
Raimbault, Jérôme, Pierre-Emmanuel Peyneau, Denis Courtier-Murias, Thomas Bigot, Jaime Gil Roca, Béatrice Béchet, and Laurent Lassabatère. "Investigating the impact of exit effects on solute transport in macroporous media." Hydrology and Earth System Sciences 25, no. 2 (February 12, 2021): 671–83. http://dx.doi.org/10.5194/hess-25-671-2021.
Full textAbstract:
Abstract. The effect of macropore flow on solute transport has spurred much research over the last forty years. In this study, non-reactive solute transport in water-saturated columns filled with porous media crossed by a macropore was experimentally and numerically investigated. The emphasis was put on the study of exit effects, whose very existence is inherent to the finite size of any experimental column. We specifically investigated the impact of a filter at the column outlet on water flow and solute transport in macroporous systems. Experiments involving breakthrough measurements and magnetic resonance imaging (MRI) showed that solute transport displayed some significant non-unidirectional features, with a strong mass exchange at the interface between the macropore and the matrix. Fluid dynamics and transport simulations indicated that this was due to the non-unidirectional nature of the flow field close to the outlet filter. The flow near the exit of the column was shown to be strongly impacted by the presence of the outlet filter, which acts as a barrier and redistributes water from the macropore to the matrix. This impact was apparent on the breakthrough curves and the MRI images. It was also confirmed by computer simulations and could, if not properly taken into account, impede the accurate inference of the transport properties of macroporous media from breakthrough experiments.
30
Qiao, Juncheng, Xianzheng Zhao, Jianhui Zeng, Guomeng Han, Shu Jiang, Sen Feng, and Xiao Feng. "The Impacts of Nano-Micrometer Pore Structure on the Gas Migration and Accumulation in Tight Sandstone Gas Reservoirs." Energies 12, no. 21 (October 28, 2019): 4102. http://dx.doi.org/10.3390/en12214102.
Full textAbstract:
The uncertainties between reservoir quality and gas migration and accumulation in tight sandstone gas reservoirs are intrinsically attributed to complex microscopic pore structures. Integrated analysis including the physical simulation experiment of gas migration and accumulation, X-ray computed tomography (X-CT), and casting thin section (CTS) were conducted on core plug samples collected from the Upper Paleozoic Permian Lower Shihezi and Shanxi tight sandstone of the Daniudi area in the Ordos Basin to investigate the impacts of pore structure on the gas migration and accumulation. Physical simulation suggested that the gas flows in migration in tight sandstone reservoirs were characterized by deviated-Darcy linear flow and non-linear flow regimes. Minimum and stable migration pressure square gradients determined by application of apparent permeability were employed as key parameters to describe gas flow. Pore structure characterization revealed that the tight sandstone reservoir was characterized by wide pore and throat size distributions and poor pore-throat connectivity. The pore–throat combinations could be divided into three types, including the macropore and coarse throat dominant reservoir, full-pore and full-throat form, and meso-small pore and fine throat dominant form. Comparative analyses indicated that pore and throat radii determined the gas flow regimes by controlling the minimum and stable migration pressure gradients. Gas accumulation capacity was dominated by the connected effective porosity, and the gas accumulation process was controlled by the cumulative effective porosity contribution from macropores to micropores. Variations in pore structures resulted in differences in gas migration and accumulation of tight sandstone reservoirs. The macropore and coarse throat-dominant and the full-pore and full-throat reservoirs exhibited greater gas migration and accumulation potentials than the small pore and fine throat dominate form.
31
Selker, John S. "Applying Preferential Flow Concepts to Horticultural Water Management." HortTechnology 6, no. 2 (April 1996): 107–10. http://dx.doi.org/10.21273/horttech.6.2.107.
Full textAbstract:
Avoiding groundwater contamination from agricultural activities is possible only if the processes that control deep percolation are understood. The source of contaminant movement to groundwater is typically through preferential flow, processes by which the bulk soil is bypassed by some part of the infiltrating water. Three mechanisms give rise to preferential flow: fingered flow, funnel flow, and macropore flow. Fingered flow occurs in coarse-textured soils and can be minimized by starting with an initially well-wetted profile. Funnel flow is likely in layered soil profiles of silt or coarser-textured soil, in which avoiding slow overirrigation is critical. Macropore flow is observed in all structured soils in which maintaining irrigation rates well below the saturated conductivity of the soil is essential. These prescriptions are quite different than conventional recommendations, which fail to consider groundwater protection.
32
Jarvis, N. J., J. Moeys, J. M. Hollis, S. Reichenberger, A. M. L. Lindahl, and I. G. Dubus. "A Conceptual Model of Soil Susceptibility to Macropore Flow." Vadose Zone Journal 8, no. 4 (November 2009): 902–10. http://dx.doi.org/10.2136/vzj2008.0137.
Full text
33
Dunn, G. H., and R. E. Phillips. "Equivalent Diameter of Simulated Macropore Systems during Saturated Flow." Soil Science Society of America Journal 55, no. 5 (September 1991): 1244–48. http://dx.doi.org/10.2136/sssaj1991.03615995005500050008x.
Full text
34
Karahan, Gülay, and Sabit Erşahin. "Relating Macropore Flow to Soil Parametric and Morphological Variables." Soil Science Society of America Journal 81, no. 5 (August 31, 2017): 1014–24. http://dx.doi.org/10.2136/sssaj2016.10.0327.
Full text
35
Alaoui, A., and B. Goetz. "Dye tracer and infiltration experiments to investigate macropore flow." Geoderma 144, no. 1-2 (March 2008): 279–86. http://dx.doi.org/10.1016/j.geoderma.2007.11.020.
Full text
36
Cullum, R. F. "Macropore flow estimations under no-till and till systems." CATENA 78, no. 1 (July 2009): 87–91. http://dx.doi.org/10.1016/j.catena.2009.03.004.
Full text
37
Rasmussen, Lars Holm, Vibeke Ernstsen, and Hans Christian Bruun Hansen. "Redoximorphic Macropore Environments in an Agrudalf." Hydrology Research 32, no. 4-5 (August 1, 2001): 333–52. http://dx.doi.org/10.2166/nh.2001.0019.
Full textAbstract:
Soil materials in fracture walls may strongly interact with solutes and colloidal particles during preferential flow. Wall coatings rich in metal oxides, clays, and organic matter may increase sorption capacities, whereas coatings devoid of these constituents have the opposite effect of increasing the risk of leaching of otherwise strongly sorbing solutes. The contrasting compositions between bulk horizon and fracture wall materials of a Typic Agrudalf excavated at Flakkebjerg, Denmark, were studied by using chemical and micromorphological methods. In the upper 220 cm of the profile, the predominant desiccation and shear fractures had 2-30 mm thick hypocoatings depleted of Fe-oxides with adjacent 5-20 mm thick quasi-coatings containing 5-6 times as much Fe-oxide. Thin hypocoatings covering walls of smaller voids and surfaces of sand particles and with strong enrichments of Fe- and Mn-oxides occurred throughout the profile, but were most abundant below 220 cm. Fracture walls, commonly with distinct laminas of clay, silt, and organic matter, generally had slightly coarser texture, but were enriched in smectite compared with horizon materials. Higher contents of organic C in fracture coatings were attributed to root growth and deposition of A-horizon materials. Despite removal of Fe-oxides from depletion hypocoatings, no corresponding depletion of P was observed. However, calculations demonstrated that, in the case of macropore transport only, P sorption capacity would be at least 5 times less than during piston-like matrix flow. For adequate estimations of solute leaching from macroporous soils there is a strong need to properly take into account sorption properties of macropore wall materials!
38
Lin, H. S., K. J. McInnes, L. P. Wilding, and C. T. Hallmark. "Low tension water flow in structured soils." Canadian Journal of Soil Science 77, no. 4 (November 1, 1997): 649–54. http://dx.doi.org/10.4141/s96-061.
Full textAbstract:
Water transport through structured clayey soils may be prone to by-pass flow, a mechanism that may lead to rapid transport of contaminants to ground water. To quantify the significance of low-tension water flow in structured soils, apparent steady-state infiltration rates at water potentials from −0.24 to 0 m were measured using tension infiltrometers on 18 soils of varying texture and structure. Each infiltration measurement was conducted sequentially at −0.24, −0.12, −0.06, −0.03, −0.02, −0.01, and 0 m supply potentials (Ψsupply), all at the same soil location, to separate different size pores effective in transmitting water. Results from 96 soil horizons showed that 76 ± 18% (mean ± SD) of the water fluxes at Ψsupply = 0 m (total water flux) were transmitted through macropores (active at Ψsupply ≥ −0.03 m), although macropores usually constituted a small portion of a soil's total porosity. Mesopores (active at Ψsupply ≥ −0.24 m) contributed 19 ± 13% of total water flux. Micropores dominated the soils' total porosities, but generally contributed <10% of the total water flux. Macropores and mesopores showed greater influence on water flow in clays than in sands at Ψsupply ≥ −0.24 m. Values of soil macroscopic λc and microscopic λm capillary length scales were determined from the change in infiltration rates with Ψsupply. Values of λc, a hydraulic conductivity-weighted mean capillary water potential, were greater for sands (63 mm) than loams (50 mm), and greater for loams than clays (22 mm). Values of λm, the mean hydraulically effective pore size, were greater for clays (0.33 mm) than loams (0.15 mm), and greater for loams than sands (0.12 mm). Most of the soils studied showed hydraulic characteristics associated with by-pass flow. Key words: Infiltration, tension infiltrometer, macropore flow, by-pass flow, capillary length scale, α parameter
39
Emerman, Steven H. "The tipping bucket equations as a model for macropore flow." Journal of Hydrology 171, no. 1-2 (September 1995): 23–47. http://dx.doi.org/10.1016/0022-1694(95)02735-8.
Full text
40
Skovdal Christiansen, Jesper, Mette Thorsen, Thomas Clausen, Søren Hansen, and Jens Christian Refsgaard. "Modelling of macropore flow and transport processes at catchment scale." Journal of Hydrology 299, no. 1-2 (November 2004): 136–58. http://dx.doi.org/10.1016/j.jhydrol.2004.04.029.
Full text
41
Liu, Muxing, Li Guo, Jun Yi, Henry Lin, Shulan Lou, Hailin Zhang, and Tian Li. "Characterising preferential flow and its interaction with the soil matrix using dye tracing in the Three Gorges Reservoir Area of China." Soil Research 56, no. 6 (2018): 588. http://dx.doi.org/10.1071/sr17238.
Full textAbstract:
Dye tracing experiments provide direct visual evidence of preferential flow in the soil. In this study, we applied the Brilliant Blue tracer across three forest sites (high-mountain forest, HF; middle-mountain forest, MF; and low-mountain forest, LF) and one cultivated field (CL) in the Three Gorges Reservoir Area of China to visualise preferential flow and characterise its interaction with the surrounding soil matrix. A set of parameters was extracted from photographs of dye-stained soil profiles to measure preferential flow, including (1) the ratio of the stained area to the total area of a soil section (SAR), (2) the degree of lateral water mixing of preferential flow into the soil matrix (LWM), (3) the greatest stained depth (SD), and (4) the stained path width (SPW). The highest SAR of all of the stained areas (i.e. a measure of the degree of preferential flow) was for MF (80%), followed by LF (68%), CL (48%), and HF (30%). The higher SAR in MF and LF was likely associated with more abundant and interconnected void spaces created by roots and soil fissures. The shallower rooting depth together with the higher content of clay and soil organic matter might lead to the lowest SAR in HF, suggesting a higher likelihood of soil erosion due to surface runoff. The relatively lower SAR in CL could be a result of soil compaction after tillage destroyed soil macropores. Moreover, the spatial distribution of preferential flow with soil depth varied among slope positions. In HF and MF, macropore flow dominated the A horizon with limited lateral diffusion. However, in the subsoil, although the SAR of all of the stained areas declined, the LWM (quantified as the SAR of yellow and green patches that have a lower concentration of the dye tracer) intensified. In the sandy soils at the LF site, macropore flow via soil fissures was the major type of preferential flow that showed a limited lateral diffusion. In CL, the degree of preferential flow (mainly as finger flows) decreased with soil depth. Based on the SPW profile, flow patterns were classified along soil depth at each site. The lower degree of preferential flow and the reduced SD in agricultural soils demonstrated the substantial impact of soil management on preferential flow and thereby infiltration. Therefore, current agricultural management exacerbates surface runoff and soil erosion and causes ecological degradation and sediment deposition in the Three Gorges Reservoir Area of China.
42
Akhtar, M. S., U. Mohrlok, and D. Stüben. "A simple two layer model for simulation of adsorbing and nonadsorbing solute transport through field soils." Hydrology and Earth System Sciences Discussions 6, no. 5 (September 4, 2009): 5631–64. http://dx.doi.org/10.5194/hessd-6-5631-2009.
Full textAbstract:
Abstract. While rapid movement of solutes through structured soils constitutes the risk of groundwater contamination, simulation of solute transport in field soils is challenging. A modification in an existing preferential flow model was tested using replicated Chloride and Lithium leachings carried out at constant flow rates through four soils differing in grades and type of structure. Flow rates generated by +10 mm, −10 mm, −40 mm, and −100 mm water heads at the surface of 35 cm diameter 50 cm height field columns. Three well-structured silty clay soils under ponding had concurrent breakthrough of Chloride and Lithium within a few cm of drainage, and a delayed and reduced peak concentration of Lithium with decrease in flow rate controlled by the negative heads. Massive sandy loam soil columns had delayed but uniform breakthrough of the solutes over the flow rates. Macropore flow in well-structured silty clay/clay loam soils reduced retardation, R (1.5 to 4.5) and effective porosity, θe (0.05 to 0.15), and increased macropore velocity, vm (20 to 30 cm cm−1 drainage) compared to the massive sandy soils. The existing simple preferential flow equation (single layer) fitted the data well only when macropore flow was dominant. The modified preferential flow equations (two layers) fitted equally well both for the adsorbing and nonadsorbing solutes. The later had high goodness of fit for a large number of solute breakthroughs, and gave almost identical retardation coefficient R as that calculated by two-domain CDE. With fewer parameters, the modified preferential flow equation after testing on some rigorous model selection criteria may provide a base for future modeling of chemical transport.
43
Sandström, Klas. "Modeling the Effects of Rainfall Variability on Groundwater Recharge in Semi-Arid Tanzania." Hydrology Research 26, no. 4-5 (August 1, 1995): 313–30. http://dx.doi.org/10.2166/nh.1995.0018.
Full textAbstract:
A conceptual model of the effects of rainfall variability on groundwater recharge was developed and applied to a small forested catchment in semi-arid Tanzania. The model simulated dual-domain recharge through the soil matrix and macropores, and was based on daily values of rainfall and potential evapotranspiration. Three different land-cover conditions (forested-nondegraded, deforested-nondegraded, and deforested-degraded) were included in the study in order to simulate the large-scale deforestation and land degradation process now occurring in Tanzania. In addition, the alternative land covers were also considered in combination with three different rainfall regimes. The results indicate the importance of macropore flow, particularly during dry years. The lack of macropores under deforested-degraded conditions reduces the simulated groundwater recharge to such an extent that it is less than under forested conditions. Simulating a climate change scenario shows that a small change in rainfall (-15%) can cause a large change in recharge (-45%).
44
Germann, Peter F. "HESS Opinions: Unsaturated infiltration – the need for a reconsideration of historical misconceptions." Hydrology and Earth System Sciences 25, no. 2 (March 2, 2021): 1097–101. http://dx.doi.org/10.5194/hess-25-1097-2021.
Full textAbstract:
Abstract. Briggs (1897) deduced capillary flow from deviation of the equilibrium between capillarity and gravity. Richards (1931) raised capillary flow to an unproven soil hydrological dogma. Attempts to correct the dogma led to concepts of non-equilibrium flow, macropore flow, and preferential flow during infiltration. Viscous film flow is proposed as an alternative approach to capillarity-driven flow during unsaturated infiltration.
45
Zehe, E., U. Ehret, T. Blume, A. Kleidon, U. Scherer, and M. Westhoff. "A thermodynamic approach to link self-organization, preferential flow and rainfall–runoff behaviour." Hydrology and Earth System Sciences 17, no. 11 (November 1, 2013): 4297–322. http://dx.doi.org/10.5194/hess-17-4297-2013.
Full textAbstract:
Abstract. This study investigates whether a thermodynamically optimal hillslope structure can, if existent, serve as a first guess for uncalibrated predictions of rainfall–runoff. To this end we propose a thermodynamic framework to link rainfall–runoff processes and dynamics of potential energy, kinetic energy and capillary binding energy in catchments and hillslopes. The starting point is that hydraulic equilibrium in soil corresponds to local thermodynamic equilibrium (LTE), characterized by a local maximum entropy/minimum of free energy of soil water. Deviations from LTE occur either due to evaporative losses, which increase absolute values of negative capillary binding energy of soil water and reduce its potential energy, or due to infiltration of rainfall, which increases potential energy of soil water and reduces the strength of capillary binding energy. The amplitude and relaxation time of these deviations depend on climate, vegetation, soil hydraulic functions, topography and density of macropores. Based on this framework we analysed the free energy balance of hillslopes within numerical experiments that perturbed model structures with respect to the surface density of macropores. These model structures have been previously shown to allow successful long-term simulations of the water balances of the Weiherbach and the Malalcahuello catchments, which are located in distinctly different pedological and climatic settings. Our findings offer a new perspective on different functions of preferential flow paths depending on the pedological setting. Free energy dynamics of soil water in the cohesive soils of the Weiherbach is dominated by dynamics of capillary binding energy. Macropores act as dissipative wetting structures by enlarging water flows against steep gradients in soil water potential after long dry spells. This implies accelerated depletion of these gradients and faster relaxation back towards LTE. We found two local optima in macropore density that maximize reduction rates of free energy of soil water during rainfall-driven conditions. These two optima exist because reduction rates of free energy are, in this case, a second-order polynomial of the wetting rate, which implicitly depends on macroporosity. An uncalibrated long-term simulation of the water balance of the Weiherbach catchment based on the first optimum macroporosity performed almost as well as the best fit when macroporosity was calibrated to match rainfall–runoff. In the Malalcahuello catchment we did not find an apparent optimum density of macropores, because free energy dynamics of soil water during rainfall-driven conditions is dominated by increases of potential energy. Macropores act as dissipative drainage structures by enhancing export of potential energy. No optimum macropore density exists in this case because potential energy change rates scale linearly with the wetting rate. We found, however, a distinguished macroporosity that assures steady-state conditions of the potential energy balance of the soil, in the sense that average storage of potential energy is compensated by average potential energy export. This distinguished macroporosity was close to the value that yielded the best fit of rainfall–runoff behaviour during a calibration exercise and allowed a robust estimate of the annual runoff coefficient. Our findings are promising for predictions in ungauged catchments (PUB) as the optimal/distinguished model structures can serve as a first guess for uncalibrated predictions of rainfall–runoff. They also offer an alternative for classifying catchments according to their similarity of the free energy balance components.
46
Silva, R. G., K. C. Cameron, H. J. Di, N. P. Smith, and G. D. Buchan. "Effect of macropore flow on the transport of surface-applied cow urine through a soil profile." Soil Research 38, no. 1 (2000): 13. http://dx.doi.org/10.1071/sr99016.
Full textAbstract:
A field lysimeter experiment was conducted to determine the effect of macropore flow on the transport of surface-applied cow urine N through soil. The lysimeters (500 mm diameter by 700 mm depth) used for this experiment were collected from Templeton fine sandy loam soil (Udic Ustochrept), which had been under ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) pasture for 9–10 years. The effect of macropore flow on urine-N leaching was determined by leaching experiments under 0.5 kPa and 0 kPa water tensions (suctions) imposed on top of the lysimeter using a disc tension infiltrometer. The 0.5 kPa suction prevented soil pores >600 µm diameter from conducting water and solutes, while the 0 kPa suction allowed conduction under ‘field saturated’ condition. Pores >600 µm diameter transmitted about 98% of the total nitrogen (N) leached below 700 mm depth. The main form of N transmitted under 0 kPa was ammonium (NH4 -N), accounting for 10.5% of the total N applied at 0 kPa suction. This was significantly higher than the amount of NH 4 -N leached at 0.5 kPa suction, which accounted for 0.17% of N applied. The urea-N in the leachate reached 16 mg/L at 0 kPa suction, and accounted for 1.6% of the total N applied. No urea was detected in the leachate at the 0.5 kPa suction. The concentrations and amounts of nitrate (NO3 -N) leached were very low and did not differ between the two suctions. The forms and amounts of N leached were affected by the interactions of macropore flow and N transformations in the soil, and the environmental conditions during the two leaching events. From this work, it is recommended that stock should be removed 1–2 days before irrigation water is applied as this will allow animal urine to diffuse into soil micropores and thus decrease N leaching by macropore flow.
47
Rastiello, Giuseppe, R. Bennacer, Georges Nahas, and Mateuz Bogdan. "Effective Permeability and Transfer Properties in Fractured Porous Media." Defect and Diffusion Forum 362 (April 2015): 172–89. http://dx.doi.org/10.4028/www.scientific.net/ddf.362.172.
Full textAbstract:
Mesoscale analyses of cracked porous volumes are performed. The fluid flows through a multiphase volume comprising one macro-crack, macro-pores and random micro-porous solid inclusions. Mesostructures are defined by thresholding of spatially correlated Gaussian random fields.Transport through macropores and crack, as well as the diffusion in micro-porous solid inclusions, are taken into account. Homogeneous (without cracks) porous volumes illustrated the asymptotical behaviors. The corresponding macroscopic permeability tensors are obtained and correlated with the geometrical/statistical properties of the analyzed porous systems. A new equivalent electrical scheme, including shunt resistance, is proposed to evaluate the apparent diffusion coefficient. Macro-cracked porous volumes are then investigated.The increases in mass flux due to the crack, as well as the mass/energy exchanges with the surrounding porous medium, are quantified by direct numerical simulation. A drying region due to the macrocrack was illustrated and the corresponding apparent permeability was identified. For different geometrical configurations (macro-porosity, micro-porosity, macro-crack orientation and aperture) we quantify the macropore –crack interlink by comparing such structure with structure without possible flow between the macro-crack and the porous structure.The equivalence scheme between mass flow in cracked porous media and heat flow in porous media was underlined.
48
Podgorney, Robert K., and Jerry P. Fairley. "Investigation of Episodic Flow from Unsaturated Porous Media into a Macropore." Vadose Zone Journal 7, no. 1 (February 2008): 332–39. http://dx.doi.org/10.2136/vzj2006.0107.
Full text
49
Luo, Lifang, Henry Lin, and John Schmidt. "Quantitative Relationships between Soil Macropore Characteristics and Preferential Flow and Transport." Soil Science Society of America Journal 74, no. 6 (November 2010): 1929–37. http://dx.doi.org/10.2136/sssaj2010.0062.
Full text
50
Guebert, Michael D., and Thomas W. Gardner. "Macropore flow on a reclaimed surface mine: infiltration and hillslope hydrology." Geomorphology 39, no. 3-4 (August 2001): 151–69. http://dx.doi.org/10.1016/s0169-555x(00)00107-0.
Full text