Comments on “Vertical Hydraulic Gradient and Run-On Water and Sediment Effects on Erosion Processes and Sediment Regimes”

Abstract This study shows a comprehensive simulation of water and sediment fluxes from the catchment to the reach scale. We describe the application of a modelling cascade in a well researched study catchment through connecting stateof- the-art public domain models in ArcGIS. Three models are used consecutively: (1) the hydrological model SWAT to evaluate water balances, sediment input from fields and tile drains as a function of catchment characteristics; (2) the onedimensional hydraulic model HEC-RAS to depict channel erosion and sedimentation along a 9 km channel onedimensionally; and (3) the two-dimensional hydraulic model AdH for simulating detailed substrate changes in a 230 m long reach section over the course of one year. Model performance for the water fluxes is very good, sediment fluxes and substrate changes are simulated with good agreement to observed data. Improvement of tile drain sediment load, simulation of different substrate deposition events and carrying out data sensitivity tests are suggested as future work. Main advantages that can be deduced from this study are separate representation of field, drain and bank erosion processes; shown adaptability to lowland catchments and transferability to other catchments; usability of the model’s output for habitat assessments.

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Numerical and experimental study of the vertical distribution of velocity and hydraulic gradient in the capillary fringe

10.5194/egusphere-egu21-9143 ◽

2021 ◽

Author(s):

Ali Mahdavi Mazdeh ◽

Stefan Wohnlich

Keyword(s):

Hydraulic Conductivity ◽

Vertical Distribution ◽

Water Content ◽

Middle Part ◽

Hydraulic Gradient ◽

Upward Movement ◽

Capillary Fringe ◽

Gradient Profile ◽

Vertical Hydraulic Gradient ◽

The Vertical Distribution

Capillary fringe plays an important role in the fate and transport of infiltrated solutes from agricultural lands. In this study, flow patterns and the vertical distribution of the velocity and hydraulic gradient inside the capillary fringe were investigated using FEFLOW calibrated by experimental data. An experimental box along with a real sample of capillary fringe from the study area (Sand and clay pit Br&#252;ggen, Germany) was used for the experiments. The dimension of the filled part of the box was 0.75 m long, 0.55 m high, and 0.150 m wide. To maintain a constant hydraulic gradient throughout the experiments the upstream and downstream groundwater levels were fixed to 7 cm and 3 cm, respectively. The horizontal velocity at different points inside the capillary fringe and the vadose zone was measured by injecting the fluorescent dye tracer (Uranin). At the end of the experiments, the soil samples are collected from different parts of the box for water content measurement. The results indicate that FEFLOW successfully estimates water content, overall flow pattern, and more importantly horizontal movement inside the capillary fringe. The streamlines are parallel to the groundwater table in the middle part.&#160; Based on both experimental and numerical results, while there is a downward movement near the outflow, an upward movement was seen near the inflow. In previous studies, the velocity profile inside the capillary fringe was estimated using Darcy&#8217;s law, unsaturated hydraulic conductivity, and constant hydraulic gradient. The detailed comparison of measured water content and velocity with numerical modeling results showed that the constant hydraulic gradient assumption above the water table in previous studies is not valid. The vertical hydraulic gradient profile calculated by FEFLOW showed that the hydraulic gradient at the middle part of the box changes from 0.042 to 0.03. Moreover, the shape of the vertical hydraulic gradient profile is a function of the location in the box and soil type.Keywords: Solute transport, Unsaturated zone, Streamline, Pore velocity, Hydraulic conductivity, FEFLOW

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Chemical variability of water and sediment over time and along a mountain river subjected to natural and human impact

Knowledge and Management of Aquatic Ecosystems ◽

10.1051/kmae/2017056 ◽

2018 ◽

pp. 5 ◽

Cited By ~ 2

Author(s):

Ewa Szarek-Gwiazda ◽

Grażyna Mazurkiewicz-Boroń ◽

Robert Gwiazda ◽

Jan Urban

Keyword(s):

Human Impact ◽

Major Ions ◽

Catchment Basin ◽

Erosion Processes ◽

Water And Sediment ◽

Physico Chemical ◽

Chemical Variability ◽

Ion Contents ◽

The Impact ◽

Over Time

We studied the variability of physico-chemical parameters in water, and heavy metal contents in water and sediment over time and along the Carpathian Biała Tarnowska River (southern Poland) and related them to catchment geology, human impact and the effect of barriers as a side aspect. The river water was well oxygenated, had pH 7.7–9.5 and was characterised by low and average flow. Temperature, pH and dissolved oxygen did not change significantly, while the contents of major ions, NO3−, NH4+, Mn and Fe increased gradually along the river. The major ion contents were negatively, and nitrate, Mn, and Fe positively, correlated with the flow. We recognise correlations between nitrate, Fe and Mn to be good indicators of soil erosion processes in the catchment. River sediment was unpolluted by most of the studied metals (slightly polluted by Ni and Cd). The differences in the values of some parameters (pH and NH4+, PO43−, HCO3−, Mn, Cd and Pb concentrations) in the water, and heavy metals in the sediment upstream and downstream of some of the barriers were determined. Spatiotemporal changes in the values of studied parameters and the results of statistical calculation indicate the impact of human activity in the catchment basin (land use, wastewater) on the water chemistry.

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Treating causes not symptoms: restoration of surface - groundwater interactions in rivers

Marine and Freshwater Research ◽

10.1071/mf09047 ◽

2009 ◽

Vol 60 (9) ◽

pp. 976 ◽

Cited By ~ 35

Author(s):

Tamao Kasahara ◽

Thibault Datry ◽

Michael Mutz ◽

Andrew J. Boulton

Keyword(s):

River Restoration ◽

Fluvial Geomorphology ◽

Hydraulic Gradient ◽

River Ecosystem ◽

Ecological Connectivity ◽

Alluvial Rivers ◽

Vertical Hydraulic Gradient ◽

Groundwater Exchange ◽

Sediment Permeability ◽

Flushing Flows

Many river restoration projects seek to address issues associated with impaired hydrological and ecological connectivity in longitudinal (e.g. effects of dams, weirs) or lateral (e.g. alienated floodplain) dimensions. Efforts to restore the vertical dimension of impaired stream–groundwater exchange are rare, hampered by limited understanding of the factors controlling this linkage in natural alluvial rivers. We propose a simplified two-axis model of the ‘primary drivers’ (sediment structure and vertical hydraulic gradient) of stream–groundwater exchange that acknowledges their interaction and provides a practical template to help researchers and river managers pose hypothesis-driven solutions to restoration of damaged or lost vertical connectivity. Many human activities impact on one or both of these drivers, and we review some of the tools available for treating the causes (rather than symptoms) in impacted stream reaches. For example, creating riffle-pool sequences along stream reaches will enhance vertical hydraulic gradient, whereas flushing flows can remove clogging layers and sustain sediment permeability. Our model is a first step to specifying mechanisms for recovery of lost vertical connectivity. Assessing results of river restoration using this approach at reach to catchment scales will provide scientific insights into the interplay of hydrology, fluvial geomorphology and river ecosystem function at appropriately broad scales.

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Impact of Vertical Hydraulic Gradient on Rill Erodibility and Critical Shear Stress

Soil Science Society of America Journal ◽

10.2136/sssaj2009.0096 ◽

2010 ◽

Vol 74 (6) ◽

pp. 1914-1921 ◽

Cited By ~ 25

Author(s):

Sayiro K. Nouwakpo ◽

Chi-hua Huang ◽

Laura Bowling ◽

Phillip Owens

Keyword(s):

Shear Stress ◽

Critical Shear Stress ◽

Hydraulic Gradient ◽

Vertical Hydraulic Gradient

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Vertical hydraulic gradient research in hyporheic zone of Beberibe river in Pernambuco State (Brazil)

RBRH ◽

10.1590/2318-0331.011615153 ◽

2016 ◽

Vol 21 (4) ◽

pp. 674-684

Author(s):

Tatiane Barbosa Veras ◽

Jaime Joaquim da Silva Pereira Cabral ◽

Anderson Luiz Ribeiro de Paiva ◽

Roberto Lima Barcellos ◽

Laércio Leal dos Santos

Keyword(s):

Grain Size ◽

Surface Water ◽

Hyporheic Zone ◽

Flow Direction ◽

Water Source ◽

Infiltration Rate ◽

Hydraulic Gradient ◽

Vertical Hydraulic Gradient ◽

Hydraulic Gradients ◽

Infiltration Tests

ABSTRACT The interaction between groundwater and surface water occurs naturally and is dependent on the dynamics in the hyporheic zone. The hyporheic zone is the interface between the surface water source and the phreatic aquifer and it’s a system that also influences the water quality. An important feature is the ability to flux in this zone. This work aimed to evaluate the vertical hydraulic gradient in the hyporheic zone at two points in Beberibe river, Olinda-PE, to understand the hyporheic environment characteristics and water flow dynamics in experimental area, in addition to identify the existence of hydraulic connection between surface water and groundwater. The experimental phase consisted of infiltration tests in riverbed with cylinder infiltrometer and vertical hydraulic gradients readings with differential piezometer, complemented with grain size information, for an assessment of the water budget between the river and the aquifer. Analyzing the behavior of the interaction over the period of 10 months, it was observed that the Beberibe river (middle course) contributes to the groundwater recharge in most of the time. The average infiltration rate was 1.02 mm/min in point 1 and 0.85 mm/min in point 2. It was concluded that there is a variability in flow direction, which often is top-down, but may undergo change in the stream showing upstream after long periods of rainfall. Another conclusion is that grain size distribution of bed sediment, that is predominantly sandy, influences hydraulic conductivity of hyporheic zone and influences consequently the vertical flow rates.

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