A 2D model for simulating heterogeneous mass and energy fluxes through melting snowpacks

Abstract. Accurate estimation of the water flux through melting snowpacks is of primary importance for runoff prediction. Lateral flows and preferential flow pathways in porous media flow have proven critical for improving soil and groundwater flow models, but though many physically-based layered snowmelt models have been developed, only 1D matrix flow over level ground is currently accounted for in snow models. Snowmelt models that include these processes may improve snowmelt discharge timing and contributing area calculations in hydrological models. A two-dimensional snow model (SMPP – Snowmelt Model with Preferential flow Paths) is presented that simulates heat and water flows through both snowpack matrix and preferential flow paths, as well as snowmelt and refreezing of meltwater. The model assumes thermodynamic equilibrium between solid and liquid phases and uses the latest improvements made in snow science to estimate snow hydraulic and thermal properties. A finite volume method is applied to solve for the 2D heat and water equations. The use of a water entry pressure for dry snow combined with consideration of the impact of heterogeneities in surface fluxes and internal snow properties – density, grain size and layer thickness – allowed calculation of the formation of preferential flow paths in the snowpack. The simulation of water flow through preferential flow paths resulted in liquid water reaching the base of the snowpack earlier than for a homogeneous wetting front. Moreover, the preferential flow paths in the model increased the exchange of energy between the snow surface and the internal snowpack, resulting in faster warming of the snowpack. A sensitivity analysis, conducted on the snow internal properties showed that initial conditions such as density and temperature, should be carefully measured in the field to accurately estimate liquid water percolating through the snowpack. Furthermore, two empirical coefficients used in the water flow equation were showed to greatly impact model outputs. This heterogeneous flow model is an important tool to help understand snowmelt flow processes in complex and level terrains and to demonstrate how uncertainty in snowmelt-derived runoff calculations might be reduced.

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Simulating ice layer formation under the presence of preferential flow in layered snowpacks

The Cryosphere ◽

10.5194/tc-10-2731-2016 ◽

2016 ◽

Vol 10 (6) ◽

pp. 2731-2744 ◽

Cited By ~ 32

Author(s):

Nander Wever ◽

Sebastian Würzer ◽

Charles Fierz ◽

Michael Lehning

Keyword(s):

Snow Cover ◽

Water Flow ◽

Liquid Water ◽

Preferential Flow ◽

Layer Formation ◽

Flow Paths ◽

One Dimensional ◽

Preferential Flow Paths ◽

Matrix Flow ◽

Dual Domain

Abstract. For physics-based snow cover models, simulating the formation of dense ice layers inside the snowpack has been a long-time challenge. Their formation is considered to be tightly coupled to the presence of preferential flow, which is assumed to happen through flow fingering. Recent laboratory experiments and modelling techniques of liquid water flow in snow have advanced the understanding of conditions under which preferential flow paths or flow fingers form. We propose a modelling approach in the one-dimensional, multilayer snow cover model SNOWPACK for preferential flow that is based on a dual domain approach. The pore space is divided into a part that represents matrix flow and a part that represents preferential flow. Richards' equation is then solved for both domains and only water in matrix flow is subjected to phase changes. We found that preferential flow paths arriving at a layer transition in the snowpack may lead to ponding conditions, which we used to trigger a water flow from the preferential flow domain to the matrix domain. Subsequent refreezing then can form dense layers in the snowpack that regularly exceed 700 kg m−3. A comparison of simulated density profiles with biweekly snow profiles made at the Weissfluhjoch measurement site at 2536 m altitude in the Eastern Swiss Alps for 16 snow seasons showed that several ice layers that were observed in the field could be reproduced. However, many profiles remain challenging to simulate. The prediction of the early snowpack runoff also improved under the consideration of preferential flow. Our study suggests that a dual domain approach is able to describe the net effect of preferential flow on ice layer formation and liquid water flow in snow in one-dimensional, detailed, physics-based snowpack models, without the need for a full multidimensional model.

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Simulating ice layer formation under the presence of preferential flow in layered snowpacks

10.5194/tc-2016-185 ◽

2016 ◽

Cited By ~ 1

Author(s):

Nander Wever ◽

Sebastian Würzer ◽

Charles Fierz ◽

Michael Lehning

Keyword(s):

Snow Cover ◽

Water Flow ◽

Liquid Water ◽

Preferential Flow ◽

Swiss Alps ◽

Layer Formation ◽

Flow Paths ◽

One Dimensional ◽

Preferential Flow Paths ◽

Dual Domain

Abstract. For physics based snow cover models, simulating the formation of dense ice layers inside the snowpack has been a long time challenge. Their formation is considered to be tightly coupled to the presence of preferential flow, which is assumed to happen through flow fingering. Recent laboratory experiments and modelling techniques of liquid water flow in snow have advanced the understanding of conditions under which preferential flow paths or flow fingers form. We propose a modelling approach in the one-dimensional, multi-layer snow cover model SNOWPACK for preferential flow that is based on a dual-domain approach. The pore space is divided into a part that represents matrix flow and a part that represents preferential flow. Richards equation is then solved for both domains. We found that preferential flow paths arriving at a layer transition in the snowpack may lead to ponding conditions. Subsequent refreezing then can form dense layers in the snowpack, that regularly exceed 700 kg m−3. A comparison of simulated density profiles with bi-weekly snow profiles made at the Weissfluhjoch measurement site at 2536 m altitude in the Eastern Swiss Alps for 16 snow seasons showed that several ice layers that were observed in the field could be reproduced. However many profiles remain challenging to simulate. The prediction of the early snowpack runoff also improved under the consideration of preferential flow. Our study suggests that a dual domain approach is able to describe the net effect of preferential flow on ice layer formation and liquid water flow in snow in one-dimensional, detailed, physics based snowpack models, without the need for a full multi-dimensional model.

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Liquid water infiltration into a layered snowpack: evaluation of a 3-D water transport model with laboratory experiments

Hydrology and Earth System Sciences ◽

10.5194/hess-21-5503-2017 ◽

2017 ◽

Vol 21 (11) ◽

pp. 5503-5515 ◽

Cited By ~ 8

Author(s):

Hiroyuki Hirashima ◽

Francesco Avanzi ◽

Satoru Yamaguchi

Keyword(s):

Liquid Water ◽

Laboratory Experiments ◽

Preferential Flow ◽

Transport Model ◽

Three Dimensional ◽

Water Infiltration ◽

Flow Paths ◽

Preferential Flow Paths ◽

Capillary Barriers ◽

Wet Snow

Abstract. The heterogeneous movement of liquid water through the snowpack during precipitation and snowmelt leads to complex liquid water distributions that are important for avalanche and runoff forecasting. We reproduced the formation of capillary barriers and the development of preferential flow through snow using a three-dimensional water transport model, which was then validated using laboratory experiments of liquid water infiltration into layered, initially dry snow. Three-dimensional simulations assumed the same column shape and size, grain size, snow density, and water input rate as the laboratory experiments. Model evaluation focused on the timing of water movement, thickness of the upper layer affected by ponding, water content profiles and wet snow fraction. Simulation results showed that the model reconstructs relevant features of capillary barriers, including ponding in the upper layer, preferential infiltration far from the interface, and the timing of liquid water arrival at the snow base. In contrast, the area of preferential flow paths was usually underestimated and consequently the averaged water content in areas characterized by preferential flow paths was also underestimated. Improving the representation of preferential infiltration into initially dry snow is necessary to reproduce the transition from a dry-snow-dominant condition to a wet-snow-dominant one, especially in long-period simulations.

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Interaction Between Plant Roots and Soil Water Flow in Response to Preferential Flow Paths in Northern China

Land Degradation and Development ◽

10.1002/ldr.2592 ◽

2016 ◽

Vol 28 (2) ◽

pp. 648-663 ◽

Cited By ~ 13

Author(s):

Yinghu Zhang ◽

Jianzhi Niu ◽

Mingxiang Zhang ◽

Zixing Xiao ◽

Weili Zhu

Keyword(s):

Soil Water ◽

Water Flow ◽

Preferential Flow ◽

Northern China ◽

Plant Roots ◽

Flow Paths ◽

Preferential Flow Paths ◽

Soil Water Flow

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Liquid water infiltration into a layered snowpack: evaluation of a 3D water transport model with laboratory experiments

10.5194/hess-2017-200 ◽

2017 ◽

Author(s):

Hiroyuki Hirashima ◽

Francesco Avanzi ◽

Satoru Yamaguchi

Keyword(s):

Water Content ◽

Liquid Water ◽

Laboratory Experiments ◽

Preferential Flow ◽

Transport Model ◽

Water Infiltration ◽

Flow Paths ◽

Preferential Flow Paths ◽

Capillary Barriers ◽

Wet Snow

Abstract. The heterogeneous movement of liquid water through snowpack during precipitation and snowmelt leads to complex liquid water distributions that are important for avalanche and runoff forecasting. We reproduced the formation of capillary barriers and the development of preferential flow through snow using a multi-dimensional water transport model, which was then validated using laboratory experiments of liquid water infiltration into layered, initially dry snow. Three-dimensional simulations assumed the same column shape and size, grain size, snow density, and water input rate as the laboratory experiments. Model evaluation focused on the timing of water movement, the thickness of the upper layer affected by ponding, and on water content profiles and the wet snow fraction. Simulation results showed that the model reconstructs some relevant features of capillary barriers including ponding in the upper layer, preferential infiltration far from the interface, and the timing of liquid water arrival at the snow base. In contrast, the area of preferential flow paths was usually underestimated and consequently the averaged water content in areas characterized by preferential flow paths was also underestimated. Improving the representation of water preferential infiltration into initially dry snow is necessary to reproduce the transition from a dry-snow-dominant condition to a wet-snow-dominant one, especially in long-period simulations.

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

Hydrology and Earth System Sciences ◽

10.5194/hess-18-121-2014 ◽

2014 ◽

Vol 18 (1) ◽

pp. 121-138 ◽

Cited By ~ 31

Author(s):

J. Wienhöfer ◽

E. Zehe

Keyword(s):

Solute Transport ◽

Water Flow ◽

Process Model ◽

Preferential Flow ◽

Quantitative Description ◽

Lateral Flow ◽

Hydrological Process ◽

Flow Paths ◽

Preferential Flow Paths ◽

Model Set

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.

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The Role of Management of Stream–Riparian Zones on Subsurface–Surface Flow Components

Water ◽

10.3390/w11091905 ◽

2019 ◽

Vol 11 (9) ◽

pp. 1905 ◽

Cited By ~ 2

Author(s):

Steiness ◽

Jessen ◽

Spitilli ◽

van’t Veen ◽

Højberg ◽

...

Keyword(s):

Preferential Flow ◽

Groundwater Discharge ◽

Surface Flow ◽

Flow Paths ◽

Flow Measurements ◽

Preferential Flow Paths ◽

Flow Components ◽

Anthropogenic Alterations ◽

The Impact ◽

Geoelectrical Methods

A managed riparian lowland in a glacial landscape (Holtum catchment, Denmark) was studied to quantify the relative importance of subsurface and surface flow to the recipient stream. The hydrogeological characterization combined geoelectrical methods, lithological logs, and piezometric heads with monthly flow measurements of springs, a ditch, and a drain, to determine seasonality and thereby infer flow paths. In addition, groundwater discharge through the streambed was estimated using temperature and water-stable isotopes as tracers. The lowland received large groundwater inputs with minimal seasonal variations from adjacent upland aquifers. This resulted in significant amounts of groundwater-fed surface flow to the stream, via man-made preferential flow paths comprising ditches, drainage systems, and a pond, and via two natural springs. Roughly, two thirds of the stream gain was due to surface flow to the stream, mainly via anthropogenic alterations. In contrast, direct groundwater discharge through the streambed accounted for only 4% of the stream flow gain, although bank seepage (not measured) to the straightened and deepened stream potentially accounted for an additional 17%. Comparison to analogous natural flow systems in the catchment substantiate the impact of anthropogenic alterations of riparian lowlands for the subsurface and surface flow components to their streams.

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Conceptualising the effect of preferential flow on slow-moving landslides: from experiments to concepts and models.

10.5194/egusphere-egu21-15777 ◽

2021 ◽

Author(s):

Thom Bogaard

Keyword(s):

Preferential Flow ◽

Water Levels ◽

Spatial And Temporal Variation ◽

Flow Paths ◽

Groundwater Levels ◽

Multiple Origins ◽

Preferential Flow Paths ◽

Landslide Body ◽

Slow Moving ◽

The Impact

<p>Precipitation is one of the main causes for the initiation or reactivation of deep seated slow moving landslides. Preferential flow paths can have multiple origins, they can be due to changes in soil water content such as desiccation, due to mechanical movement or due to biological activity. The overarching characteristic is that they strongly alter the hydraulic properties of the landslide material. This results in a complex hydrological behaviour of deep-seated slow moving landslides. Research has shown that for instance the porosity of the soil, the fissure distribution and fissure connectivity are very important to predict the behaviour of the hydrological response of precipitation within a landslide body. However, due to large heterogeneity of landslide lithology and spatial and temporal variation of a landslide, it is hard to model water levels in landslides. Cracks and fissures inside the landslide are the cause of preferential flow paths, which can work as infiltration networks to the groundwater, but also as drainage networks lowering the (perched) groundwater levels.</p><p>In the last decades, both methodological progress has been made and several case studies have been published. However, most are still somewhat anecdotic examples and a more overarching conceptualisation has not been made yet. In this overview I want to highlight the progress as well as obstacles and challenges ahead of us when assessing and quantifying the impact of preferential flow paths on the mechanisms of a slow moving deep-seated landslide and to improve our understanding and modelling of complex landslides.</p>

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The impact of soil development, rainfall intensity and vegetation complexity on subsurface flow paths along a glacial chronosequence of 10 millennia

10.5194/hess-2021-242 ◽

2021 ◽

Author(s):

Anne Hartmann ◽

Markus Weiler ◽

Konrad Greinwald ◽

Theresa Blume

Keyword(s):

Bulk Density ◽

Vegetation Cover ◽

Preferential Flow ◽

Landscape Evolution ◽

Subsurface Flow ◽

Flow Paths ◽

Hydrologic Processes ◽

Preferential Flow Paths ◽

Irrigation Intensity ◽

The Impact

Abstract. Hydrologic processes play an important role in the hydro-pedo-geomorphological feedback cycle of landscape evolution. Soil properties and subsurface flow paths change over time, but due to lack of observations important hydrologic processes such as water flow paths are often not properly considered in soil and landscape evolution studies. We investigated the evolution of subsurface flow paths during landscape development in the calcareous glacier forefield at the Griessfirn in the Swiss Alps. While the main focus was on flow path evolution and the formation of preferential flow paths with soil development, we also looked at the impact of irrigation intensity and vegetation complexity (in what way does the vegetation complexity defined by degree of vegetation cover and functional diversity at each age class relate to subsurface structures and flow path initialization?). We chose four glacial moraines of different ages (110, 160, 4 900, and 13 500 years) and conducted dye tracer experiments with Brilliant Blue (4 g l−1) on three plots at each moraine. The three plots at each age class differed by their degree of vegetation complexity (low, medium, and high) and each was further divided into three equal subplots where dyed water was applied with three different irrigation intensities (20, 40, and 60 mm h−1) and an irrigation amount of 40 mm. Dye pattern characteristics in form of volume density and surface area density were derived by digital image analysis and compared via statistical analysis.Volume density was used to classify the observed dye patterns into specific flow type categories. The effect of soil formation and thus changing soil characteristics on flow types were investigated by the analysis of structural and textural parameters in form of grain size distribution, porosity, bulk density, and loss on ignition. A change in flow types with increasing moraine age was observed from a rather homogeneous matrix flow to heterogeneous matrix and finger flow. Along the soil chronosequence, a reduction in particle sizes and an ongoing vegetation development resulted in an accumulation of organic matter in the topsoil and an increase in water storage capacity (decrease in bulk density and increase in porosity). Differences in irrigation intensity only had an effect on flow types at the oldest moraine, where the frequency of finger flow decreased with increasing irrigation intensity. A relation between vegetation complexity and flow types was only observed at the older moraines, which had a dense vegetation cover. With increasing vegetation complexity the proportion of preferential flow paths in form of finger flow also increased.

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