Multiple tracing of fast solute transport in a drained grassland soil
Introduction
The flow patterns occurring in natural and managed soils are in many, if not most cases, highly irregular. This irregularity is often called preferential flow, which means that part of the water and solutes move rapidly through a small portion of the soil without much exchange with the surrounding soil matrix over a substantial length of the flow domain (Flühler et al., 1996). The flow velocities are large and even strongly sorbing solutes like pesticides Flury, 1996, Flury et al., 1995, Kladivko et al., 2001, phosphorus Addiscott et al., 2000, Heckrath et al., 1995, Hergert et al., 1981a, Hergert et al., 1981b, Sims et al., 1998, Stamm et al., 1998 or radionuclides (Bundt et al., 2000) may reach groundwater or subsurface drainage systems before being sorbed or biologically degraded.
Due to the large sampling volume, subsurface drainage systems are sometimes taken as ideal experimental systems for transport phenomena in soils Czapar and Kanwar, 1991, Flury, 1996, Gish et al., 2000, Lennartz et al., 1999. Such studies rely on the assumption that sampling large volumes averages out the small-scale spatial heterogeneities. Classical drainage theory assumes a vertical transport through the unsaturated and a predominantly lateral flow through the saturated zone towards the drain. If this concept was true and preferential transport into the drains observed an interconnected system of vertical and lateral preferred flow paths should exist. This has been shown, e.g., for some heavy clay soils Inoue, 1993, Ruland et al., 1991 or for forest soils (Luxmoore et al., 1990).
We have found preferential P transport into subsurface drains in weakly structured loamy soils (Stamm et al., 1998). Based on infiltration experiments, we concluded that vertical worm burrows are the main macropore structures in our study region. In one case, we observed lateral transport of a dye tracer and we could attribute this to a dense network of well-preserved ancient root channels in the saturated zone. Such structures are rather exceptional features. Therefore, it is not evident what the lateral preferred flow paths towards a tile drain are in weakly structured soils. The purpose of this paper is to investigate the fast transport into a subsurface drain in such a soil and to study how the lateral distance to the drains affects the fast solute transport. We carried out a sprinkling experiment on a drained grassland plot. The flow paths were assessed based on the breakthrough behavior of spatially separated tracers, hydrometric data and infiltration patterns in the soil.
Section snippets
Site description
The study site is situated in a subcatchment (“Kleine Aa”) of Lake Sempach in the central Swiss Plateau at an altitude of 585 m a.s.l. (Schweizerische Landestopographie, coordinates 659,100/221,000). The mean air temperature is about 7.5 °C and the mean annual precipitation amounts to 1200 mm. The soil has developed from glacial till (Würm glaciation) and is classified as a loamy, frigid to mesic Oxyaquic Eutrochrept (Soil Survey Staff, 1992), characterized by periodic waterlogging as well as
Spatial and temporal variation of the water table in the field
As expected, the level of the water table was substantially higher between two drains than in the immediate vicinity of the drains (Fig. 4). The drainage system was functional despite its age of about 50 years. During February 1996, snow (62.5 mm) fell on frozen ground and melted at the end of the month. The melting water raised the water table from February 6 to 28 close to the surface followed by a pronounced decrease during the dry period from February 28 to March 11. The dynamics of the
Discussion
In our experiment, solutes were quickly transported vertically as well as laterally over considerable distances of several meters. This fast transport affected not only a small percentage of the solutes but also up to 20–40% of the applied tracer mass. Because the hydrometric data showed that the contributing water volume was small—in the order of few millimeters to centimeters only—one may ask where this transport took place within the soil.
In an earlier experiment at a smaller scale (2 m2),
Conclusions
Often, surface runoff and subsurface flow are treated as separate processes in the sense that water or solutes are thought to be transported to open waters by either one of the two. Considering our findings, this clear distinction gets blurred. Instead of two parallel processes, transport may be a sequence of two where water may (first) move laterally as (near-) surface runoff that is intercepted by preferred flow paths in the vicinity of subsurface drains.
This has also consequences for the
Acknowledgements
We would like to thank the many people who helped in the field or in the laboratory: F. Denoth, H. Feyen, M. Flühler, F. Funk, G. Gal, H. Hoffmann-Riehm, J. Hollinger, A. Keller, B. Kulli, S. Lampert, H. Läser, P. Lehmann, A. Mares, R. Meuli, B. von Steiger, B. Studer and V. Vouets. R. Höfling helped us by analyzing the deuterium samples. P. Lazzarotto provided the precipitation data of the Sempach weather station. We want to thank also the farmer and landowner, Mr. Rindlisbacher, who agreed on
References (42)
- et al.
Lateral solute mixing processes—a key for understanding field-scale transport of water and solutes
Geoderma
(1996) - et al.
Water movement and isoproturon behaviour in a drained heavy clay soil: 1. Preferential flow processes
J. Hydrol.
(1994) Lateral water flow in a clayey agricultural field with cracks
Geoderma
(1993)- et al.
Physical and chemical controls of preferred path flow through a forested hillslope
Geoderma
(1990) - et al.
Soil erosion via preferential flow to drainage systems in clay soils
Geoderma
(1997) - et al.
Tile drain sampling of preferential flow on a field scale
J. Contam. Hydrol.
(1988) - et al.
Occupancy and geometrical properties of Lumbricus terrestris L. burrows affecting infiltration
Pedobiologia
(1999) - et al.
Influence of improved subsurface drainage on phosphorus losses and nitrogen leaching from a heavy clay soil
Agric. Water Manage.
(1995) - et al.
Phosphate losses through field drains in a heavy cultivated soil
J. Environ. Qual.
(2000) Bodenkundliche Kartieranleitung
(1982)
Impact of preferential flow on radionuclide distribution in soil
Environ. Sci. Technol.
Field measurement of preferential flow using subsurface drainage tiles
Non-ideal drains
Bestimmung von Ammonium-Stickstoff mit Fliessanalyseverfahren (E23)
Experimental evidence of transport of pesticides through field soils—a review
J. Environ. Qual.
Transport of anions and herbicides in a loamy and a sandy field soil
Water Resour. Res.
Quantifying dye tracers in soil profiles by image analysis
Eur. J. Soil Sci.
Methodical studies for D/H-isotope analysis—a new technique for the direct coupling of sample preparation to an IRMS
Isotopes Environ. Health Stud.
A new sample preparation device for quantitative hydrogen isotope analysis using chromium metal
Anal. Chem.
Managerial impacts on preferential fluid dynamics
Phosphorus leaching from soils containing different phosphorus concentrations in the Broadbalk experiment
J. Environ. Qual.
Cited by (75)
Analysis of seasonal variation in the hydrological behaviour of a field combining surface and tile drainage
2023, Agricultural Water ManagementComparing alternative conceptual models for tile drains and soil heterogeneity for the simulation of tile drainage in agricultural catchments
2022, Journal of HydrologyCitation Excerpt :The degree of saturation in fine-textured agricultural soils is often controlled by subsurface drainage systems, consisting of tile drains, to improve root development and crop yield. By controlling the elevation of the groundwater table, tile drains alter both the hydrologic flow pathways in agricultural catchments (Hansen et al., 2013; King et al., 2014; Thomas et al., 2016; Werner et al., 2016) and the rates of nutrient transport from croplands to surface water bodies (Amado et al., 2017; Radcliffe et al., 2015; Rozemeijer et al., 2010b; Stamm et al., 2002). The inclusion of tile drainage in numerical models is therefore necessary for the proper simulation of hydrological processes in highly managed agricultural areas.
An analysis of the spatio-temporal occurrence of anthelmintic veterinary drug residues in groundwater
2021, Science of the Total EnvironmentCitation Excerpt :Transport of contaminants to the groundwater below the poorly drained soils may be facilitated by preferential flow through the soil via macropores, as demonstrated by Weiss et al. (2008) who report loss rates of up to 16% of BZs via preferential flow beneath permanent pastures. Transport may also occur via surface or near surface pathways (particularly with heavy rainfall) (Stamm et al., 2002; Kreuzig et al., 2007) to features such as karstic sinking streams, which can then provide further rapid groundwater transport via conduits. The latter of these seems a potentially plausible explanation, with 3 of the 5 minPD sites with detections being karstic springs which are known to be fed by conduit flow with rapid travel times.
Quantifying the contribution of tile drainage to basin-scale water yield using analytical and numerical models
2019, Science of the Total EnvironmentCitation Excerpt :In intensely tiled agricultural regions, the environmental consequences of subsurface tiling are profound and well-documented. Subsurface drainage increases the amount of nitrate lost from agricultural landscapes (Carluer and De Marsily, 2004; Jaynes et al., 2001; Kladivko et al., 2004; Rozemeijer et al., 2010; Sands et al., 2008; Skaggs et al., 1994; Stamm et al., 2002; Van den Eertwegh et al., 2006; van der Velde et al., 2010), causes a decrease in groundwater travel times (Schilling et al., 2015; David et al., 2010; Gentry et al., 2009; McIsaac and Hu, 2004), bypasses riparian buffers (Schilling et al., 2015; Dinnes et al., 2002), and reduces the extent of denitrification in upland regions (Skaggs et al., 1994) of agricultural watersheds. Tile drainage has also been implicated in excessive loss of dissolved phosphorus (Schilling et al., 2018; King et al., 2015; Smith et al., 2015).
Effects of artificial land drainage on hydrology, nutrient and pesticide fluxes from agricultural fields – A review
2018, Agriculture, Ecosystems and EnvironmentCitation Excerpt :However, under certain conditions, infiltration excess can also be a relevant process in humid zones (Doppler et al., 2012). For subsurface flows, the process of preferential flow also needs to be considered, since it has been found to significantly enhance flow velocities through the soil profile (Flury et al., 1994) and into drainage systems (Stamm et al., 2002). Preferential flow includes all transport pathways in all types of soil, thereby circumventing flows through the soil matrix.
Fluorescent tracers to evaluate pesticide dissipation and transformation in agricultural soils
2018, Science of the Total Environment
- 1
Present address: ProCert Safety AG, Thunstr. 17, 3000 Bern 6, Switzerland.