Lateral Flow Paths Research Articles

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

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

Assessing the effect of puddling on preferential flow processes through under bund area of lowland rice field

High water losses from rice fields and continued detection of nitrates in groundwater in rice growing areas are two important challenges of sustainable rice production. Recent studies have shown that preferential flow paths present in under-bund soils is a major reason behind such water and nitrogen losses in lowland rice soils. The present study was conducted to comprehensively characterize water flow and nitrogen transport processes in typical rice soils of eastern India. Detailed soil characterization and several flow and transport experiments conducted in undisturbed soil cores and directly under field conditions were used to estimate fate and transport parameters for preferential transport models. Experimental assessment also included data from plugged bunds where the under-bund soils were puddled to create a low-permeable soil layer. Results showed that the under-bund soils are generally more permeable than the within-field soils. The layer between the plow sole and the clay pan may have naturally evolved to serve as lateral flow path while the presence of isolated yet vertically connected high permeable zones through the clay pans may be serving as localized recharge pits in rice soils. Results of transport experiments suggested that although the presence of plow sole in within-field soil can significantly increase solute residence time, urea-N may bypass much of the soil matrix and get transported through the preferential flow paths of under-bund soil before it gets hydrolyzed. Such bypassing may also occur in rice vadose zone through localized patches of relatively high permeable soil or through leaky plow soles. Results further showed that bund plugging may effectively increase the retention time for solutes in within-field soils. Results of model parameterization suggested that preferential transport parameters estimated using the dual-permeability model could provide an acceptable prediction of urea-N transport behaviour in rice soils.

Linking Subsurface Lateral Flowpath Activity with Streamflow Characteristics in a Semiarid Headwater Catchment

Linking Subsurface Lateral Flowpath Activity with Streamflow Characteristics in a Semiarid Headwater Catchment

A porewater-based stable isotope approach for the investigation of subsurface hydrological processes

Abstract. Predicting and understanding subsurface flowpaths is still a crucial issue in hydrological research. We present an experimental approach to reveal present and past subsurface flowpaths of water in the unsaturated and saturated zone. Two hillslopes in a humid mountainous catchment have been investigated. The H2O(liquid) – H2O(vapor) equilibration laser spectroscopy method was used to obtain high resolution δ2H vertical depth profiles of pore water at various points along two fall lines of a pasture hillslope in the southern Black Forest, Germany. The Porewater-based Stable Isotope Profile (PSIP) approach was developed to use the integrated information of several vertical depth profiles of deuterium along transects at the hillslope. Different shapes of depth profiles were observed in relation to hillslope position. The statistical variability (inter-quartile range and standard deviation) of each profile was used to characterize different types of depth profiles. The profiles upslope or with a weak affinity for saturation as indicated by a low topographic wetness index preserve the isotopic input signal by precipitation with a distinct seasonal variability. These observations indicate mainly vertical movement of soil water in the upper part of the hillslope before sampling. The profiles downslope or at locations with a strong affinity for saturation do not show a similar seasonal isotopic signal. The input signal is erased in the foothills and a large proportion of pore water samples are close to the isotopic values of δ2H in streamwater during base flow conditions indicating the importance of the groundwater component in the catchment. Near the stream indications for efficient mixing of water from lateral subsurface flow paths with vertical percolation are found.

The Hydrological Effects of Lateral Preferential Flow Paths in a Glaciated Watershed in the Northeastern USA

Despite observational evidence of lateral preferential flow paths in northeastern U.S. watersheds, their effects on the sources of runoff remain unclear. An intense field survey was undertaken during the 2007 growing season to determine the sources of stream runoff from a 2.51 km2 watershed in the Catskill Mountains, New York State. Lateral preferential flow paths are caused by groundwater springs and soil piping in this region. A two‐component hydrograph separation using δ18O showed that event water (rain water) was a significant source of runoff during nine rainfall events (from July to October). With these rainfall events, 14 to 37% of the volume and 18 to 49% of the peak streamflow was attributable to event water. Further, end‐member mixing analysis (EMMA), using δ18O, Si, and dissolved organic carbon (DOC), showed that saturated areas accounted for 2 to 24% of the total volume and 4 to 59% of peak streamflow but that groundwater was the dominant source of runoff volume during all events. Field surveys of saturated areas also suggested that near‐stream areas were insufficient to generate the observed stream chemistry during rainfall events larger than 8 mm. A connection with the hillside saturated areas was therefore required to explain the results of the hydrograph separations, which were corroborated by the timing of the transient (perched) groundwater and overland flow. The hydrometric measurements confirmed that hillside lateral preferential flow paths rapidly transported water to near‐stream saturation areas during runoff events under relatively dry antecedent conditions. A qualitative comparison with conventional techniques for distributing variable saturation areas (VSA) using surface topography and soil transmissivity (i.e., topographic index and soil topographic index), which do not consider the effects of lateral preferential flow paths, demonstrated that typical parameterizations (on the order of <10−1 m) would not have the spatial resolution to represent the measured lateral preferential flow paths (on the order of <10−3 m). Overall, the results suggest that the lateral redistribution of water from hillside areas reduces the influence of surface topography and channel topology on the sources of stream runoff, a finding that is consistent with recent ones from other landscapes where glacial soils have coevolved with the terrestrial hydrology.

Simulation and validation of concentrated subsurface lateral flow paths in an agricultural landscape

Abstract. The importance of soil water flow paths to the transport of nutrients and contaminants has long been recognized. However, effective means of detecting concentrated subsurface flow paths in a large landscape are still lacking. The flow direction and accumulation algorithm based on single-direction flow algorithm (D8) in GIS hydrologic modeling is a cost-effective way to simulate potential concentrated flow paths over a large area once relevant data are collected. This study tested the D8 algorithm for simulating concentrated lateral flow paths at three interfaces in soil profiles in a 19.5-ha agricultural landscape in central Pennsylvania, USA. These interfaces were (1) the interface between surface plowed layers of Ap1 and Ap2 horizons, (2) the interface with subsoil water-restricting clay layer where clay content increased to over 40%, and (3) the soil-bedrock interface. The simulated flow paths were validated through soil hydrologic monitoring, geophysical surveys, and observable soil morphological features. The results confirmed that concentrated subsurface lateral flow occurred at the interfaces with the clay layer and the underlying bedrock. At these two interfaces, the soils on the simulated flow paths were closer to saturation and showed more temporally unstable moisture dynamics than those off the simulated flow paths. Apparent electrical conductivity in the soil on the simulated flow paths was elevated and temporally unstable as compared to those outside the simulated paths. The soil cores collected from the simulated flow paths showed significantly higher Mn content at these interfaces than those away from the simulated paths. These results suggest that (1) the D8 algorithm is useful in simulating possible concentrated subsurface lateral flow paths if used with appropriate threshold value of contributing area and sufficiently detailed digital elevation model (DEM); (2) repeated electromagnetic surveys can reflect the temporal change of soil water storage and thus is a useful indicator of possible subsurface flow path over a large area; and (3) observable Mn distribution in soil profiles can be used as a simple indicator of water flow paths in soils and over the landscape; however, it does require sufficient soil sampling (by excavation or augering) to possibly infer landscape-scale subsurface flow paths. In areas where subsurface interface topography varies similarly with surface topography, surface DEM can be used to simulate potential subsurface lateral flow path reasonably so the cost associated with obtaining depth to subsurface water-restricting layer can be minimized.

Transient storage processes in a steep headwater stream

AbstractThis study examined hyporheic exchange flow and transient storage processes within a steep headwater stream, using both hydrometric and tracer approaches. Vertical hydraulic gradients varied systematically with location within step‐pool units, with upwelling located in a relatively narrow zone immediately below the step. Downward hydraulic gradients were greatest immediately above channel steps, and in that zone, gradients were also correlated with step height. Hydraulic conductivity tended to be lower in downwelling zones than in upwelling and neutral locations. Transient storage areas determined from reach‐scale tracer tests tended to increase with discharge, whereas transient exchange coefficients were not correlated with discharge. Transient storage exchange fluxes estimated from the reach‐scale tracer tests were an order of magnitude greater than hyporheic exchange fluxes estimated by scaling up local estimates based on Darcy's Law and piezometer measurements. This difference could be explained by the presence of lateral hyporheic flow paths and/or the influences of transient storage in pools. Tracer injections into infiltrometers using Rhodamine WT and sodium chloride allowed visual determination of hyporheic discharge zones and calculation of residence times for hyporheic flow through the step (pool inflow) and transport through the downstream pool (pool outflow). These tests indicated that residence time in pools can be comparable to hyporheic residence times, although the lack of replication in time and space limits the drawing of strong inferences. Copyright © 2009 John Wiley & Sons, Ltd.

Dye staining and excavation of a lateral preferential flow network

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

A GIS‐Based Tool for Spatial and Distributed Hydrological Modelling: CLASS Spatial Analyst

AbstractCLASS Spatial Analyst is a GIS tool which can be used to support spatially distributed hydrological modelling. The tool generates a number of spatial layers that can be used for many practical applications. These include climate zoning, multi‐resolution DEMs, Compound Topographic Index (CTI) (also referred to as Topographic Wetness Index, TWI), lateral multiple flow paths, accumulation and dispersion of water and solutes from hazard areas, estimation of soil depth, soil material/horizon distribution and soil moisture storage capacity in different parts of the landscape. Although each of these tasks can be undertaken separately using spatial software packages such as ArcGIS, GRASS, TIME, and MapInfo, this tool puts together all these tasks into a single application which provides the user with an option of undertaking some or all of them within this application. The technology used in this tool is supported by various peer‐reviewed publications (e.g. Tarboton 1997, Gallant and Dowling 2003).

Lateral Hyporheic Zone Chemistry in an Artificially Constructed Gravel Bar and a Re‐Meandered Stream Channel, Southern Ontario, Canada1

Abstract: The effect of stream restoration on hyporheic functions has been neglected, although channel rehabilitation projects have a potential to alter stream‐ground‐water interactions. The present study examined the effect of an artificially constructed gravel bar and re‐meandered stream channel on lateral hyporheic exchange flow and chemistry in two lowland N‐rich streams in southern Ontario, Canada. Nitrate concentrations were relatively high, ranging from 0.5 to 1.3 mg N/l in both streams during spring through fall months. However, nitrate concentrations showed a steep decline as stream water entered the gravel bar and the meander bends. Differences between observed and predicted nitrate concentrations based on conservative ion concentration patterns indicated that 40‐100 and 68‐98% of the nitrate entering the hyporheic zone was removed in the gravel bar and meanders, respectively. Rapid depletion of dissolved oxygen concentrations along lateral hyporheic flow paths and denitrifying potentials assayed by the acetylene block technique in hyporheic sediments suggests that denitrification was an important mechanism of nitrate depletion. Despite the high rate of nitrate removal, the flux of stream water laterally entering the constructed gravel bar and meander bends was very small, and hyporheic nitrate removal was <0.015% of the daily stream load during base‐flow periods in summer and fall. The effects of restoration projects on hyporheic zone dynamics are often limited in lowland streams by low channel gradients and fine floodplain sediments with low interstitial flows that restrict the magnitude of the stream‐hyporheic connection.

Mitigation of Shallow Groundwater Nitrate in a Poorly Drained Riparian Area and Adjacent Cropland

Riparian ecosystems, through their unique position in the agricultural landscape and ability to influence nutrient cycles, can potentially reduce NO3 loading to surface and ground waters. The purpose of this study was to determine the fate of NO3 in shallow groundwater moving along a lateral flowpath from a grass seed cropping system through an undisturbed mixed-species herbaceous riparian area. Soil A (30-45 cm) and C horizon (135-150 cm) NO3, dissolved oxygen, and nitrous oxide concentrations were significantly higher in the cropping system than the adjacent riparian area. Nitrate concentrations in both horizons of the riparian soil were consistently at or below 0.05 mg N L(-1) while cropping system concentrations ranged from 1 to 12 mg N L(-1). Chloride data suggested that NO3 dilution occurred from recharge by precipitation. However, a sharp decrease in NO3/Cl ratios as water moved into the riparian area indicated that additional dilution of NO3 concentrations was unlikely. Riparian area A horizon soil water had higher dissolved organic carbon than the cropping system and when the riparian soil became saturated, available electron acceptors (O2, NO3) were rapidly reduced. Dissolved inorganic carbon was significantly higher in the riparian area than the cropping system for both horizons indicating high biological activity. Carbon limitation in the cropping system may have led to microbial respiration using primarily O2 and to a lesser degree NO3. Within 6 m of the riparian/cropping system transition, NO3 was virtually undetectable.

Estimation of denitrification potential in a karst aquifer using the 15N and 18O isotopes of NO 3 −

A confined aquifer in the Malm Karst of the Franconian Alb, South Germany was investigated in order to understand the role of the vadose zone in denitrifiaction processes. The concentrations of chemical tracers Sr2+ and Cl− and concentrations of stable isotope 18O were measured in spring water and precipitation during storm events. Based on these measurements a conceptual model for runoff was constructed. The results indicate that pre-event water, already stored in the system at the beginning of the event, flows downslope on vertical and lateral preferential flow paths. Chemical tracers used in a mixing model for hydrograph separation have shown that the pre-event water contribution is up to 30%. Applying this information to a conceptual runoff generation model, the values of δ15N and δ18O in nitrate could be calculated. Field observations showed the occurence of significant microbial denitrification processes above the soil/bedrock interface before nitrate percolates through to the deeper horizon of the vadose zone. The source of nitrate could be determined and denitrification processes were calculated. Assuming that the nitrate reduction follows a Rayleigh process one could approximate a nitrate input concentration of about 170 mg/l and a residual nitrate concentration of only about 15%. The results of the chemical and isotopic tracers postulate fertilizers as nitrate source with some influence of atmospheric nitrate. The combined application of hydrograph separation and determination of isotope values in δ15N and δ18O of nitrate lead to an improved understanding of microbial processes (nitrification, denitrification) in dynamic systems.

Tectonic drivers for vegetation patterning and landscape evolution in the Albany River region of the Hudson Bay Lowlands

Summary Groundwater–peatland interactions were assessed by a regional survey in the Hudson Bay Lowlands, where the rapid rate of isostatic uplift has perturbed hydrological flow systems across a 6000‐year chronosequence. A 24 000 km2 study area along the Albany River consists of 55% fen, 35% bog and 10% mineral soil. The peatland vegetation may be further subdivided into 11 noda, which are closely related to different water levels, ranges in water chemistry, and peat landform type. Species richness generally declines with increasing water level and acidity, whereas the gradient from bog to extremely rich fen is marked by the changing abundance and occurrence of fen‐indicator species. Bog landforms are restricted to physiographic settings where surface waters flow downwards and the bog vegetation is therefore isotated from the influence of geogenous waters. In contrast, fens are located in areas where mineral solutes are transported to the peat surface either by upwelling groundwater or by advective/dispersion along lateral flow paths. Peatlands spread across the study area between 6000 and 3000 bp, coinciding with the emergence of new land from the sea. The release of organic acids from the nearly continuous peat cover acidified this calcareous landscape, leading to the convergence of the surface‐water chemistry into four discrete groupings of pH vs. calcium. Isostatic uplift, however, continues to alter the topography, fluvial geometry and groundwater flow systems of the lowlands, maintaining diverse peatland types on land surfaces of similar age. The formation of water‐table mounds under the interfluvial divides and rising moraine system spurred the development of raised bogs, whereas the formation of regional seepage faces for goundwater on the margins of the moraine and rivers of the till plain maintains large areas of fen. Although peatland succession seems to follow predictable pathways within a given hydrogeological setting, these pathways are locally altered by tectonic drivers that continually modify surface and groundwater flow systems. In this large peat basin the pace and pathway of peatland succession seems to be driven by tectonic rather than climatic forcing.

Factors controlling riffle‐scale hyporheic exchange flows and their seasonal changes in a gaining stream: A three‐dimensional groundwater flow model

Subsurface flow within a single riffle of a low‐gradient gravel bed stream was modeled in three dimensions using MODFLOW, a finite difference groundwater flow model. Model simulations showed that exchange flows can only occur in this low‐gradient, gaining stream because of a zone of alluvial sediment around the stream that has much higher permeability than the surrounding catchment (K = 10−4 m s−1, compared with K = 10−6 to 10−8 m s−1). The key factors controlling exchange flow within the alluvial zone were identified as the hydraulic conductivity of the alluvium, the hydraulic gradient between upstream and downstream ends of the riffle, and the flux of groundwater entering the alluvium from the sides and beneath. In the study riffle each of these factors changes with season, causing a reversal of flow paths in the alluvium and a reduction in exchange flows from about 0.2–0.5 m3 d−1 per meter stream length in summer to about 0.008–0.04 m3 d−1 per meter stream length during fall to spring. The model also revealed that exchange flows are up to twice as strong, but more variable, at the sides of the stream than near the center, and that vertical flow paths beneath the channel are more persistent under the range of conditions modeled than lateral flow paths into the banks.

Integrated high-resolution geophysical investigations as potential tools for water resource investigations in karst terrain

Karstic aquifers can be particularly vulnerable to both pollution from surface activities and large-scale dewatering from mineral winning operations. This is because of the enhanced vertical and lateral flow paths, resulting from the dissolution of carbonate species by rainfall. Often this process results in the development of voids that can range in size from several centimetres to several tens of metres. To date, groundwater vulnerability maps for England and Wales, including karst areas, have been produced using a methodology that does not consider the presence of karst features. The uncertainties that are presented by the potential for pollution by the presence of water-carrying conduits in karst areas, where there are proposed or existing limestone quarries, require new techniques for detecting and delineating underground cave systems. In order for any mapping technique to provide an acceptable assessment of vulnerability, the location and spatial distribution of high permeability flow paths need to be established. Of the available geophysics techniques that may allow for the identification of such features, microgravity and resistivity imaging are likely to be the most successful. Microgravity surveying has the potential to identify the presence and location of such voids, and with the integration of electrical tomographic work, can provide 'targets' for the location of monitoring boreholes. Whilst these techniques are intensive and may not be cost effective on a regional scale, they do have the potential to provide high-resolution data over smaller areas, which would be invaluable to any site or area-specific assessment of vulnerability.

Coupled vertical and lateral preferential flow on a forested slope

Coupling of vertical and lateral preferential flow paths was examined on a forested slope with thin soil cover during artificial irrigations. Point‐scale infiltration was measured at sites with differing soil macroporosities using vertical profiles of time domain reflectometry probes and suction samplers. Lateral fluxes of water and solutes from the slope were determined at a through flow trench. Sites with greater macroporosities tended to exhibit vertical preferential flow, while infiltration at sites with relatively small macroporosities was largely by vertical propagation of a well defined wetting front through the soil profile. Generation of vertical preferential flow at sites with relatively large macroporosities increased with input intensity. Lateral macropores made a minor contribution to slope runoff. Instead, runoff largely occurred in a thin saturated layer at the soil‐bedrock interface, both in a highly conductive zone at the bedrock surface and in the overlying saturated soil matrix. Some assumptions underlying the use of isotopic and geochemical tracers to study runoff generation are called into question by complex mixing of event and pre‐event water in this saturated layer. Soil depth, bedrock topography, and antecedent soil wetness determine the thickness, connectivity, and upslope extent of the pre‐event saturated layer above the bedrock surface. These, in turn, control whether vertical preferential and matrix flow reaching the bedrock surface participate in slope runoff.

Determining Fault Permeability from Subsurface Barometric Pressure

Measured barometric pressure fluctuations in a borehole drilled 600 m into the unsaturated zone at a site on the eastern slope of Yucca Mountain, Nevada, are used to compute pneumatic diffusivities and air permeabilities of layered tuffaceous rocks. Of particular interest is the occurrence of increasing pressure amplitude and decreasing phase lags observed at several deep stations. The pressure amplitude increases by 13% and the pressure peak arrives 65 to 72 h earlier as the depth of the unsaturated zone increases from 407 to 436 m. This observation is inconsistent with a conventional 1D downward pressure decay model, but can be explained by hypothesizing the existence of a lateral pneumatic flow path from a nearby fault. A 2D numerical model has been constructed to test this lateral flow hypothesis. The modeling results indicate that a leaky-fault hypothesis can reconcile the measured barometric data with other geologic mapping and permeability measurements at the site. The inferred fault permeability r...

Hydrologic flowpaths in tropical rainforest soilscapes—a review

AbstractAn Erratum has been published for this article in Hydrological Processes 15(14) 2001, 2863.A conceptual framework of hillslope hydrological response patterns and their environmental controls is used to evaluate past and present research sites in tropical rainforests with regard to their predominant controls and hydrological functioning. This evaluation highlights the importance of near‐surface flowpaths for runoff generation in Acrisol landscapes, and lack thereof in Ferralsol landscapes. Both soil types tentatively define the width of a spectrum of possible hillslope hydrologic flowpaths, from predominantly vertical to predominantly lateral flowpaths. This result allows the testing of hypotheses concerning the soil geographical occurrence of particular processes of runoff generation even where soil hydraulic data are not available. Copyright © 2001 John Wiley & Sons, Ltd.

Thermal and free carrier concentration mapping during ESD event in smart Power ESD protection devices using an improved laser interferometric technique

Spatial distribution of temperature and free-carrier concentration during high-current stress is studied in smart power electrostatic discharge (ESD) protection devices using a backside laser interferometric technique. The method is based on detecting changes in the refractive index of silicon due to thermo-optical and plasma-optical effects. We use a modified version of a heterodyne interferometer, where the reference beam is reflected from an external mirror outside the sample chip, which allows one to perform measurements without any restriction to the size of the scanning area. We have found two pronounced heat dissipating regions due to a vertical and a lateral current flow path in the device. In addition, two regions with increased current density due to carrier injection related to the two current paths have been found. These temperature and carrier concentration distributions found by the experiment agree very well with the results of 2D device simulation.

Variability of Lake Inlet Chemistry and Its Relation to Soils

The pedological analysis of the soil continuum in a catchment can yield substantial insight in flow paths, transport processes and possible linkages between terrestrial and aquatic ecosystems. In an interdisciplinary study (Sommer et al., 1997) we investigated precipitation, lake tributaries and soils of three sandstone-dominated subcatchments of a dystrophic cirque lake of the northern Black Forest during 1989 and 1990. The chemistry of tributary 1 is characterized by relatively higher pH-values, positive alkalinity at baseflow, higher concentrations of Ca, Mg, and K, and lower DOC. It does not fit the chemistry of the very acid, leached, podzolized soils in the catchment (weak linkage). The dominance of baseflow and lower intra-annual variations in discharge and temperature further confirms the conclusion of a dominating vertical flow path of soil water into the regolith and bedrock zone with substantial buffering in that zone (groundwater flow). Tributary 2 shows the lowest pH-values and the highest concentrations of DOC, Fe, AI, and P, which fits very well the chemistry of the very acid, leached, permanently wet soils of its catchment (strong linkage). The dominance of storm flow water with high intra-annual variations in discharge corresponds with the high soil moisture and prevalent lateral flow path of water in the soil cover (lateral subsurface flow). Tributary 'mix behaves intermediate between tributaries 1 and 2 but is more similar to that of tributary 1. This is due to the dominance of podzolized over reductomorphic soils in the subcatchment. Lateral transport of matter can be inferred from the soil pattern in all catchments, but its relevance for lake inlet chemistry depends on the existence of downslope immobilization zones.