Field-scale variation of preferential flow as indicated from dye coverage

2002 ◽  
Vol 257 (1-4) ◽  
pp. 164-173 ◽  
Author(s):  
P Öhrström ◽  
M Persson ◽  
J Albergel ◽  
P Zante ◽  
S Nasri ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Field Scale ◽  
Scale Variation

Upscaling transport of Bacillus subtilis endospores and phiX174 coliphages in heterogeneous porous media from the column to the field scale

2021 ◽  
Author(s):  
Thomas Oudega ◽  
Gerhard Lindner ◽  
Julia Derx ◽  
Andreas Farnleitner ◽  
Regina Sommer ◽  
...  
Keyword(s):  
Porous Media ◽  
Bacillus Subtilis ◽  
Groundwater Contamination ◽  
Preferential Flow ◽  
Heterogeneous Porous Media ◽  
Field Scale ◽  
Column Tests ◽  
Removal Rates ◽  
Linear Processes ◽  
Sandy Gravel

<p>Groundwater contamination and subsequent transport of viruses and bacteria are a major concern in aquifers worldwide. To ascertain the ability of these aquifers to remove pathogens, tracer tests with microbial indicators are carried out. But because these tests are laborious and require special permission, column tests are often done instead. Unfortunately, results from column tests tend to grossly overestimate removal rates λ when compared to the field scale, which can lead to underestimations of groundwater contamination risks. Scale is an important consideration when examining pathogen transport through porous media, as pathogen removal rarely happens by linear processes. Field tests were carried out with Bacillus subtilis endospores and phiX174 coliphages over a distance of 25 m in an alluvial gravel aquifer in Vienna, Austria. The sandy gravel material from the field site was also used in column tests with the same tracers. Both attachment-detachment and Colloid Filtration Theory were used to model these tests. The results show a big difference in removal between the two scales. A comparison with the literature showed a correlation between the heterogeneity (or preferential flow) of the porous media and the difference in removal rates between the column and field scale.</p>

Tile drain sampling of preferential flow on a field scale

1988 ◽  
Vol 3 (2-4) ◽  
pp. 307-325 ◽  
Author(s):  
Tom L. Richard ◽  
Tammo S. Steenhuis
Keyword(s):  
Preferential Flow ◽  
Field Scale

Field-Scale Variation in Microbial Activity and Soil Properties in Relation to Mineralization and Sorption of Pesticides in a Sandy Soil

2008 ◽  
Vol 37 (5) ◽  
pp. 1710-1718 ◽  
Author(s):  
F. P. Vinther ◽  
U. C. Brinch ◽  
L. Elsgaard ◽  
L. Fredslund ◽  
B.V. Iversen ◽  
...  
Keyword(s):  
Soil Properties ◽  
Microbial Activity ◽  
Sandy Soil ◽  
Field Scale ◽  
Scale Variation

scholarly journals Field experimental design for pesticide leaching – a modified large-scale lysimeter

2005 ◽  
Vol 7 ◽  
pp. 41-44
Author(s):  
Bertel Nilsson ◽  
Jens Aamand ◽  
Ole Stig Jacobsen ◽  
René K. Juhler
Keyword(s):  
Large Scale ◽  
Preferential Flow ◽  
Fracture Network ◽  
Transport Processes ◽  
Natural Fracture ◽  
Field Scale ◽  
Flow Paths ◽  
Undisturbed Soil ◽  
Flow And Transport ◽  
Preferential Flow Paths

Recent research on Danish groundwater has focused on clarifying the fate and transport of pesticides that leach through clayey till aquitards with low matrix permeability. Previously, these aquitards were considered as protective layers against contamination of underlying groundwater aquifers due to their low permeability characteristics. However, geological heterogeneities such as fractures and macropores have been recognised as preferential flow paths within low permeable clayey till (e.g. Beven & Germann 1982). The flow velocities within these preferential flow paths can be orders of magnitude higher than in the surrounding clay matrix and pose a major risk of transport of contaminants to the underlying aquifers (e.g. Nilsson et al. 2001). Previous studies of transport in fractured clayey till have focused on fully saturated conditions (e.g. Sidle et al. 1998; McKay et al. 1999). However, seasonal fluctuations of the groundwater table typically result in unsaturated conditions in the upper few metres of the clay deposits, resulting in different flow and transport conditions. Only a few experiments have examined the influence of unsaturated conditions on flow and solute (the dissolved inorganic and organic constituents) transport in fractured clayey till. These include smallscale laboratory column experiments on undisturbed soil monoliths (e.g. Jacobsen et al. 1997; Jørgensen et al. 1998), intermediate scale lysimeters (e.g. Fomsgaard et al. 2003) and field-scale tile drain experiments (e.g. Kjær et al. 2005). The different approaches each have limitations in terms of characterising flow and transport in fractured media. Laboratory studies of solute transport in soils (intact soil columns) are not exactly representative of field conditions due to variations in spatial variability and soil structure. In contrast, field studies hardly allow quantification of fluxes and mechanisms of transport. Column and lysimeter experiments are often limited in size, and tile-drain experiments on field scale do not provide spatial resolution and often have large uncertainties in mass balance calculations. Thus, in order to represent the overall natural fracture network systems on a field scale with respect to acquiring insights into flow and transport processes, the lysimeter needs to be larger than normal lysimeter size (< 1 m3). A modified large-scale lysimeter was therefore constructed by the Geological Survey of Denmark and Greenland (GEUS) at the Avedøre experimental field site 15 km south of Copenhagen (Fig. 1). This lysimeter consisted of an isolated block (3.5 ×3.5 ×3.3 m) of unsaturated fractured clayey till with a volume sufficient to represent the overall preferential flow paths (natural fracture network) within lowpermeable clayey till at a field scale.

scholarly journals Critical Role of Preferential Flow in Field-Scale Pathogen Transport and Retention

2017 ◽  
Vol 16 (4) ◽  
pp. vzj2016.12.0127 ◽  
Author(s):  
Scott A. Bradford ◽  
Feike J. Leij ◽  
Jack Schijven ◽  
Saeed Torkzaban
Keyword(s):  
Preferential Flow ◽  
Critical Role ◽  
Field Scale ◽  
Pathogen Transport

scholarly journals Field scale effective hydraulic parameterisation obtained from TDR time series and inverse modelling

2009 ◽  
Vol 6 (2) ◽  
pp. 1489-1522 ◽  
Author(s):  
U. Wollschläger ◽  
T. Pfaff ◽  
K. Roth
Keyword(s):  
Time Series ◽  
Hydraulic Properties ◽  
Preferential Flow ◽  
Time Domain Reflectometry ◽  
Inverse Modelling ◽  
Soil Conditions ◽  
Small Scale ◽  
Field Scale ◽  
Time Period

Abstract. Due to the large heterogeneity in the hydraulic properties of natural soils, estimation of field scale effective hydraulic parameters is difficult. Past research revealed that data from accurate but small scale laboratory measurements could hardly ever be transferred to the field scale. In this study, we explore an alternative approach where hydraulic properties of a layered soil profile are directly estimated from hydraulic inverse modelling using a time series of in situ measured soil water contents obtained from time domain reflectometry. Simulations were conducted for natural boundary conditions and run for a one-year time period including both wet and dry soil conditions. For the time period used for inversion, the model is able to reproduce the general evolution of water content in the different soil layers reasonably well. However, distinct drying and wetting events could not be reproduced in detail which we explain by the complex natural processes that are not included in the rather simple model, e.g. an accurate site-specific representation of the evapotranspiration process and, potentially, preferential flow. The study emphasizes the importance of a correct representation of the various processes occuring in the soil-plant-atmosphere continuum. Still, we conclude that – for time periods where measured data for calibration are available – this simple estimation of effective hydraulic properties from in situ data is a good approach to obtain effective parameters for describing unsaturated water movement in field soils which are not dominated by complex processes like preferential flow.

scholarly journals Understanding the Relative Importance of Vertical and Horizontal Flow in Ice-Wedge Polygons

2019 ◽  
Author(s):  
Nathan A. Wales ◽  
Jesus D. Gomez-Velez ◽  
Brent D. Newman ◽  
Cathy J. Wilson ◽  
Baptiste Dafflon ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Horizontal Flow ◽  
Relative Importance ◽  
Water Fluxes ◽  
Field Scale ◽  
Flow And Transport ◽  
Hydrological Characteristics ◽  
Warming Climate ◽  
Conservative Tracer ◽  
Ice Wedge

Abstract. Ice-wedge polygons are common Arctic landforms. The future of these landforms in a warming climate depends on the bidirectional feedback between the rate of ice-wedge degradation and changes in hydrological characteristics. This work aims to better understand the relative roles of vertical and horizontal water fluxes in the subsurface of polygonal landscapes, providing new insights and data to test and calibrate hydrology models. Field-scale investigations were conducted at an intensively-instrumented location on the Barrow Environmental Observatory (BEO) near Utqiaġvik, AK, USA. Using a conservative tracer, we examined controls of microtopography and the frost table on subsurface flow and transport within a low-centered and a high-centered polygon. Bromide tracer was applied at both polygons in July 2015 and transport was monitored through two thaw seasons. Samplers arrays placed in polygon centers, rims, and troughs were used to monitor tracer concentrations. In both polygons, the tracer first infiltrated vertically until encountering the frost table, then was transported horizontally. Horizontal flow occurred in more locations and at higher velocities of fluxes in the low-centered polygon than in the high-centered polygon. Preferential flow, influenced by frost table topography, was significant between polygon centers and troughs. Estimates of horizontal hydraulic conductivity were within the range of previous estimates of vertical conductivity, highlighting the importance of horizontal flow in these systems. This work forms a basis for understanding complexity of flow in polygonal landscapes.

Using dye tracer for visualizing roots impact on soil structure and soil porous system

Biologia ◽  
2015 ◽  
Vol 70 (11) ◽  
Author(s):  
Radka Kodešová ◽  
Karel Němeček ◽  
Anna Žigová ◽  
Antonín Nikodem ◽  
Miroslav Fér
Keyword(s):  
Water Uptake ◽  
Soil Structure ◽  
Preferential Flow ◽  
Soil Surface ◽  
Water Infiltration ◽  
Porous System ◽  
Field Scale ◽  
Thin Sections ◽  
Dye Tracer ◽  
The Impact

AbstractPlants influence the water regime in soil by both water uptake and an uneven distribution of water infiltration at the soil surface. The latter process is more poorly studied, but it is well known that roots modify soil structure by enhancing aggregation and biopore production. This study used a dye tracer to visualize the impact of plants on water flow in the topsoil of a Greyic Phaeozem. Brilliant blue was ponded to 10 cm height in a 1 m × 1 m frame in the field immediately after harvest of winter wheat (Triticum aestivum L.). After complete infiltration, the staining patterns within the vertical and horizontal field-scale sections were studied. In addition, soil thin sections were made and micromorphological images were used to study soil structure and dye distribution at the microscale. The field-scale sections clearly documented uneven dye penetration into the soil surface, which was influenced by plant presence and in some cases by mechanical compaction of the soil surface. The micromorphological images showed that root activities compress soil and increases the bulk density near the roots (which could be also result of root water uptake and consequent soil adhesion). On the other hand in few cases a preferential flow along the roots was observed.

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