Relevance and controls of preferential flow at the landscape scale

Demand, Dominic; Blume, Theresa; Weiler, Markus

doi:10.5194/hess-2019-80

Cited by 3 publications

(11 citation statements)

References 59 publications

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“…The observed differences were likely related to wetter conditions (e.g., less bypass flow due to hydrophobicity, larger hydraulic conductivity of the matrix) in the deforested part of the catchment (Figure 3) and the larger amount of direct rainfall (no interception). Whereas the results presented here showed clear differences in sequential flow occurrence, several earlier studies have reported clear differences in preferential flow occurrence that were related to different vegetation types [27,39,40,49]. Alaoui et al [27] found preferential flow both in forest and in grassland soil, but dye patterns suggested stronger interactions between macropores and matrix for forest soils.…”

Section: Analysis Of Differences In Sensor Response Due To Deforestationcontrasting

confidence: 69%

“…The macropores in the grassland soils, on the other hand, showed little interaction with the surroundings. Jin et al [39] and Demand et al [40] found clear differences in preferential flow occurrence between grassland and forested sites. Zhao et al [49] also observed more preferential flow occurrence for a forest site as compared to a grassland site.…”

Section: Analysis Of Differences In Sensor Response Due To Deforestationmentioning

confidence: 96%

“…The macropores in the grassland soils, on the other hand, showed little interaction with the surroundings. Jin et al [39] and Demand et al [40] found Overall, clear changes in sequential and no flow occurrence were observed, which could directly be linked to the partial deforestation in the Wüstebach catchment. The observed differences were likely related to wetter conditions (e.g., less bypass flow due to hydrophobicity, larger hydraulic conductivity of the matrix) in the deforested part of the catchment (Figure 3) and the larger amount of direct rainfall (no interception).…”

Section: Analysis Of Differences In Sensor Response Due To Deforestationmentioning

confidence: 96%

“…In recent years, soil moisture response time analysis has been introduced, and this type of analysis offers more quantitative spatiotemporal information on the occurrence of preferential and piston flow in the subsurface [34][35][36][37][38][39][40]. The aim of this study is to use a sensor response time analysis to investigate changes in subsurface flow behavior related to partial deforestation in a small headwater catchment in Germany.…”

Section: Introductionmentioning

confidence: 99%

“…The aim of this study is to use a sensor response time analysis to investigate changes in subsurface flow behavior related to partial deforestation in a small headwater catchment in Germany. Two recent studies by Jin et al [39] and Demand et al [40] already used such an analysis to characterize differences in flow behavior related to vegetation. Both studies showed that the occurrence of preferential flow and the infiltration capacity can be significantly larger in forests as compared to grassland sites.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Deforestation on Water Flow in the Vadose Zone

Wiekenkamp

Huisman

Bogena

et al. 2019

Water

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The effects of land use change on the occurrence and frequency of preferential flow (fast water flow through a small fraction of the pore space) and piston flow (slower water flow through a large fraction of the pore space) are still not fully understood. In this study, we used a five year high resolution soil moisture monitoring dataset in combination with a response time analysis to identify factors that control preferential and piston flow before and after partial deforestation in a small headwater catchment. The sensor response times at 5, 20 and 50 cm depths were classified into one of four classes: (1) non-sequential preferential flow, (2) velocity based preferential flow, (3) sequential (piston) flow, and (4) no response. The results of this analysis showed that partial deforestation increased sequential flow occurrence and decreased the occurrence of no flow in the deforested area. Similar precipitation conditions (total precipitation) after deforestation caused more sequential flow in the deforested area, which was attributed to higher antecedent moisture conditions and the lack of interception. At the same time, an increase in preferential flow occurrence was also observed for events with identical total precipitation. However, as the events in the treatment period (after deforestation) generally had lower total, maximum, and mean precipitation, this effect was not observed in the overall occurrence of preferential flow. The results of this analysis demonstrate that the combination of a sensor response time analysis and a soil moisture dataset that includes pre-and post-deforestation conditions can offer new insights in preferential and sequential flow conditions after land use change.

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Section: Analysis Of Differences In Sensor Response Due To Deforestationcontrasting

confidence: 69%

Section: Analysis Of Differences In Sensor Response Due To Deforestationmentioning

confidence: 96%

Section: Analysis Of Differences In Sensor Response Due To Deforestationmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effects of Deforestation on Water Flow in the Vadose Zone

Wiekenkamp

Huisman

Bogena

et al. 2019

Water

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A soil moisture monitoring network to characterize karstic recharge and evapotranspiration at five representative sites across the globe

Berthelin¹,

Rinderer²,

Andreo³

et al. 2019

Preprint

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Abstract. Karst systems that are characterized by a high subsurface heterogeneity are posing a challenge to study their complex recharge processes. Experimental methods to study karst processes mostly focus on characterizing the entire aquifer. Despite their important role for recharge processes, the limited focus has been given on studies of the soil and epikarst and most available research has been performed at sites of similar latitudes. In our study, we describe a new monitoring concept that allows the improvement of soil and epikarst processes understanding by covering different karst systems with different land cover at different climate regions. First, we describe the site selection and the experimental setup. Then we describe the five individual sites and their soil profiles. We also present some preliminary data and highlight the potential of the data for future research aimed at answering the relevant research questions: (1) How do the soil and epikarst heterogeneities influence water flow and storage processes in the karst vadose zone? (2) What is the impact of the land cover type on karstic groundwater recharge and evapotranspiration? (3) What is the impact of climate on karstic groundwater recharge and evapotranspiration? In order to answer these questions, we monitor soil moisture, which controls the partitioning of rainfall into infiltration, soil water storage, evapotranspiration, and groundwater recharge processes. We installed a soil moisture-monitoring network at five different climate regions: in Puerto Rico (tropical), Spain (Mediterranean), the United Kingdom (humid oceanic), Germany (humid mountainous), and Australia (dry semi-arid). At each of the five sites, we defined two 20 m × 20 m plots to install soil moisture probes under different land use types (forest and grassland). At each plot, 15 soil moisture profiles were installed with probes at different depths from the top soil to the epikarst (over 400 soil moisture probes were installed). Our first results show that the monitoring network provides new insights into the soil moisture dynamics of the five study sites and that significant differences prevail among forest and grassland sites. Some profiles are characterized by sequential reactions of soil moisture, i.e., the uppermost probe reacts first and the lowest probe reacts last, while at other profiles, we find non-sequential reactions that we interpret to result from preferential flow processes. While the former favours storage in the soil providing water for evapotranspiration, the latter can be seen as an indicator for the initiation of fast and preferential recharge into the karst system. Covering the spatiotemporal variability of these processes through a large number of installed probes, our monitoring network will allow to develop a new conceptual understanding of evapotranspiration and groundwater recharge processes in karst regions across different climate regions and land use types, and provide the base for quantitative assessment with physically-based modelling approaches in the future.

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Characterizing hillslope-stream connectivity with a joint event analysis of stream and groundwater levels

Beiter¹,

Weiler²,

Blume³

2020

Preprint

Self Cite

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Abstract. Hillslope-stream connectivity controls runoff generation, both during events and baseflow conditions. However, assessing subsurface connectivity is a challenging task, as it occurs in the hidden subsurface domain where water flow cannot 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. A newly developed data analysis scheme of separating the aspects of (a) response timing and (b) extent of water level change 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- 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 catchment-scale connectivity and event response. 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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Relevance and controls of preferential flow at the landscape scale

Cited by 3 publications

References 59 publications

Effects of Deforestation on Water Flow in the Vadose Zone

Effects of Deforestation on Water Flow in the Vadose Zone

A soil moisture monitoring network to characterize karstic recharge and evapotranspiration at five representative sites across the globe

Characterizing hillslope-stream connectivity with a joint event analysis of stream and groundwater levels

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