Spatio-temporal relevance and controls of preferential flow at the landscape scale

Demand, Dominic; Blume, Theresa; Weiler, Markus

doi:10.5194/hess-23-4869-2019

Cited by 63 publications

(65 citation statements)

References 94 publications

(149 reference statements)

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“…This approach is increasingly important as technology enables observations with higher spatiotemporal resolutions and for longer durations. For example, unmanned aerial vehicles, such as those used in this and prior studies, offer sub-meter-scale observations (Wigmore et al, 2019), commercially available high-resolution (3 m) satellite images provide broad spatial coverage (Planet Team, 2017), and in situ soil moisture sensor arrays yield real-time sub-hourly data feeds and long-term monitoring (e.g., Demand et al, 2009;Oroza et al, 2018). Our unsupervised cluster analysis distilled many observations into clear and related soil moisture behaviors, and similar approaches identified characteristic time series of plant productivity in mountainous regions (Devadoss et al, 2020).…”

Section: A Dialogue Between Datasets and Predictionsmentioning

confidence: 99%

From Patch to Catchment: A Statistical Framework to Identify and Map Soil Moisture Patterns Across Complex Alpine Terrain

et al. 2020

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Climate warming in alpine regions is changing patterns of water storage, a primary control on alpine plant ecology, biogeochemistry, and water supplies to lower elevations. There is an outstanding need to determine how the interacting drivers of precipitation and the critical zone (CZ) dictate the spatial pattern and time evolution of soil water storage. In this study, we developed an analytical framework that combines intensive hydrologic measurements and extensive remotely-sensed observations with statistical modeling to identify areas with similar temporal trends in soil water storage within, and predict their relationships across, a 0.26 km2 alpine catchment in the Colorado Rocky Mountains, U.S.A. Repeat measurements of soil moisture were used to drive an unsupervised clustering algorithm, which identified six unique groups of locations ranging from predominantly dry to persistently very wet within the catchment. We then explored relationships between these hydrologic groups and multiple CZ-related indices, including snow depth, plant productivity, macro- (102->103 m) and microtopography (<100-102 m), and hydrological flow paths. Finally, we used a supervised machine learning random forest algorithm to map each of the six hydrologic groups across the catchment based on distributed CZ properties and evaluated their aggregate relationships at the catchment scale. Our analysis indicated that ~40–50% of the catchment is hydrologically connected to the stream channel, lending insight into the portions of the catchment that likely dominate stream water and solute fluxes. This research expands our understanding of patch-to-catchment-scale physical controls on hydrologic and biogeochemical processes, as well as their relationships across space and time, which will inform predictive models aimed at determining future changes to alpine ecosystems.

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Section: A Dialogue Between Datasets and Predictionsmentioning

confidence: 99%

From Patch to Catchment: A Statistical Framework to Identify and Map Soil Moisture Patterns Across Complex Alpine Terrain

et al. 2020

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“…Hillslope-stream connectivity controls runoff generation (Detty and McGuire, 2010a;Jencso et al, 2010;Penna et al, 2015;Scaife and Band, 2017) and the export of solutes, pesticides (Ocampo et al, 2006;Jackson and Pringle, 2010), and particulate matter (Thompson et al, 2013). Understanding patterns, controls and dynamics of hillslope-stream connectivity is therefore of interest not only for flood prediction but also for water quality management and policy making.…”

Section: Introductionmentioning

confidence: 99%

Characterising hillslope–stream connectivity with a joint event analysis of stream and groundwater levels

Beiter

Weiler

Blume

2020

Hydrol. Earth Syst. Sci.

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Abstract. Hillslope–stream connectivity controls runoff generation, during events and during baseflow conditions. However, assessing subsurface connectivity is a challenging task, as it occurs in the hidden subsurface domain where water flow can not be easily observed. We therefore investigated if the results of a joint analysis of rainfall event responses of near-stream groundwater levels and stream water levels could serve as a viable proxy for hillslope–stream connectivity. The analysis focuses on the extent of response, correlations, lag times and synchronicity. As a first step, a new data analysis scheme was developed, separating the aspects of (a) response timing and (b) extent of water level change. This provides new perspectives on the relationship between groundwater and stream responses. In a second step we investigated if this analysis can give an indication of hillslope–stream connectivity at the catchment scale. Stream water levels and groundwater levels were measured at five different hillslopes over 5 to 6 years. Using a new detection algorithm, we extracted 706 rainfall response events for subsequent analysis. Carrying out this analysis in two different geological regions (schist and marls) allowed us to test the usefulness of the proxy under different hydrological settings while also providing insight into the geologically driven differences in response behaviour. For rainfall events with low initial groundwater level, groundwater level responses often lag behind the stream with respect to the start of rise and the time of peak. This lag disappears at high antecedent groundwater levels. At low groundwater levels the relationship between groundwater and stream water level responses to rainfall are highly variable, while at high groundwater levels, above a certain threshold, this relationship tends to become more uniform. The same threshold was able to predict increased likelihood for high runoff coefficients, indicating a strong increase in connectivity once the groundwater level threshold was surpassed. The joint analysis of shallow near-stream groundwater and stream water levels provided information on the presence or absence and to a certain extent also on the degree of subsurface hillslope–stream connectivity. The underlying threshold processes were interpreted as transmissivity feedback in the marls and fill-and-spill in the schist. The value of these measurements is high; however, time series of several years and a large number of events are necessary to produce representative results. We also find that locally measured thresholds in groundwater levels can provide insight into the connectivity and event response of the corresponding headwater catchments. If the location of the well is chosen wisely, a single time series of shallow groundwater can indicate if the catchment is in a state of high or low connectivity.

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“…The presumption of q unsat > K sat opens an new view on shear flow and the basics of infiltration that are in stark contrast to Richards' capillary flow, where a priori K sat > K(θ or ψ). Comparisons of the rates from field infiltration with K sat -measurements in the laboratory vaguely support the presumption of [45] and [52] most recently provide experimental evidence of q unsat > K sat .…”

Section: Newton's Shear Flow Vis-à-vis Darcy's Law and Forchheimer's mentioning

confidence: 93%

Viscosity Controls Rapid Infiltration and Drainage, Not the Macropores

Germann

2020

Water

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The paper argues that universal approaches to infiltration and drainage in permeable media pivoting around capillarity and leading to dual porosity, non-equilibrium, or preferential flow need to be replaced by a dual process approach. One process has to account for relatively fast infiltration and drainage based on Newton's viscous shear flow, while the other one draws from capillarity and is responsible for storage and relatively slow redistribution of soil water. Already in the second half of the 19th Century were two separate processes postulated, however, Buckingham's and Richards' apparent universal capillarity-based approaches to the flow and storage of water in soils dominated. The paper introduces the basics of Newton's shear flow in permeable media. It then presents experimental applications, and explores the relationships of Newton's shear flow with Darcy's law, Forchheimer's and Richards' equations, and finally extends to the transport of solutes and particles.

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Spatio-temporal relevance and controls of preferential flow at the landscape scale

Cited by 63 publications

References 94 publications

From Patch to Catchment: A Statistical Framework to Identify and Map Soil Moisture Patterns Across Complex Alpine Terrain

From Patch to Catchment: A Statistical Framework to Identify and Map Soil Moisture Patterns Across Complex Alpine Terrain

Characterising hillslope–stream connectivity with a joint event analysis of stream and groundwater levels

Viscosity Controls Rapid Infiltration and Drainage, Not the Macropores

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