scholarly journals Modelling hyporheic processes for regulated rivers under transient hydrological and hydrogeological conditions

2014 ◽  
Vol 11 (8) ◽  
pp. 9327-9359
Author(s):  
D. Siergieiev ◽  
L. Ehlert ◽  
T. Reimann ◽  
A. Lundberg ◽  
R. Liedl
Keyword(s):  
Hydraulic Conductivity ◽  
Numerical Model ◽  
Wave Amplitude ◽  
Overland Flow ◽  
Analytical Models ◽  
Hyporheic Exchange ◽  
Groundwater Abstraction ◽  
River Bank ◽  
Wave Duration ◽  
Solute Fluxes

Abstract. Understanding the effects of major hydrogeological controls on hyporheic exchange and bank storage is essential for river water management, groundwater abstraction, restoration and ecosystem sustainability. Analytical models cannot adequately represent complex settings with, for example, transient boundary conditions, varying geometry of surface water–groundwater interface, unsaturated and overland flow, etc. To understand the influence of parameters such as (1) sloping river banks, (2) varying hydraulic conductivity of the riverbed and (3) different river discharge wave scenarios on hyporheic exchange characteristics such as (a) bank storage, (b) return flows and (c) residence time, a 2-D hydrogeological conceptual model and, subsequently, an adequate numerical model were developed. The numerical model was calibrated against observations in the aquifer adjacent to the hydropower regulated Lule River, Northern Sweden, which has predominantly diurnal discharge fluctuations during summer and long-lasting discharge peaks during autumn and winter. Modelling results revealed that bank storage increased with river wave amplitude, wave duration and smaller slope of the river bank, while maximum exchange flux decreased with wave duration. When a homogeneous clogging layer covered the entire river–aquifer interface, hydraulic conductivity positively affected bank storage. The presence of a clogging layer with hydraulic conductivity < 0.001 m d−1 significantly reduced the exchange flows and virtually eliminated bank storage. The bank storage return/fill time ratio was positively related to wave amplitude and the hydraulic conductivity of the interface and negatively to wave duration and bank slope. Discharge oscillations with short duration and small amplitude decreased bank storage and, therefore, the hyporheic exchange, which has implications for solute fluxes, redox conditions and the spawning potential of riverbeds. Based on these results, river regulation strategies can be improved by considering the effect of certain wave event configurations on hyporheic exchange to ensure harmonious hydrogeochemical functioning of the river–aquifer interfaces and related ecosystems.

scholarly journals Modelling hyporheic processes for regulated rivers under transient hydrological and hydrogeological conditions

2015 ◽  
Vol 19 (1) ◽  
pp. 329-340 ◽  
Author(s):  
D. Siergieiev ◽  
L. Ehlert ◽  
T. Reimann ◽  
A. Lundberg ◽  
R. Liedl
Keyword(s):  
Hydraulic Conductivity ◽  
Numerical Model ◽  
Wave Amplitude ◽  
Overland Flow ◽  
Analytical Models ◽  
Hyporheic Exchange ◽  
Groundwater Abstraction ◽  
River Bank ◽  
Wave Duration ◽  
Solute Fluxes

Abstract. Understanding the effects of major hydrogeological controls on hyporheic exchange and bank storage is essential for river water management, groundwater abstraction, restoration and ecosystem sustainability. Analytical models cannot adequately represent complex settings with, for example, transient boundary conditions, varying geometry of surface water–groundwater interface, unsaturated and overland flow, etc. To understand the influence of parameters such as (1) sloping river banks, (2) varying hydraulic conductivity of the riverbed and (3) different river discharge wave scenarios on hyporheic exchange characteristics such as (a) bank storage, (b) return flows and (c) residence time, a 2-D hydrogeological conceptual model and, subsequently, an adequate numerical model were developed. The numerical model was calibrated against observations in the aquifer adjacent to the hydropower-regulated Lule River, northern Sweden, which has predominantly diurnal discharge fluctuations during summer and long-lasting discharge peaks during autumn and winter. Modelling results revealed that bank storage increased with river wave amplitude, wave duration and smaller slope of the river bank, while maximum exchange flux decreased with wave duration. When a homogeneous clogging layer covered the entire river–aquifer interface, hydraulic conductivity positively affected bank storage. The presence of a clogging layer with hydraulic conductivity < 0.001 m d−1 significantly reduced the exchange flows and virtually eliminated bank storage. The bank storage return/fill time ratio was positively related to wave amplitude and the hydraulic conductivity of the interface and negatively to wave duration and bank slope. Discharge oscillations with short duration and small amplitude decreased bank storage and, therefore, the hyporheic exchange, which has implications for solute fluxes, redox conditions and the potential of riverbeds as fish-spawning locations. Based on these results, river regulation strategies can be improved by considering the effect of certain wave event configurations on hyporheic exchange to ensure harmonious hydrogeochemical functioning of the river–aquifer interfaces and related ecosystems.

Modelling river bank erosion using a 2D depth-averaged numerical model of flow and non-cohesive, non-uniform sediment transport

2016 ◽  
Vol 93 ◽  
pp. 75-88 ◽  
Author(s):  
Kamal El Kadi Abderrezzak ◽  
Andrés Die Moran ◽  
Pablo Tassi ◽  
Riadh Ata ◽  
Jean-Michel Hervouet
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Bank Erosion ◽  
River Bank ◽  
River Bank Erosion

scholarly journals Dating the Irrigation System of the Samarkand Oasis: A Geoarchaeological Study

Radiocarbon ◽  
2012 ◽  
Vol 54 (1) ◽  
pp. 91-105 ◽  
Author(s):  
Luca C Malatesta ◽  
Sébastien Castelltort ◽  
Simone Mantellini ◽  
Vincenzo Picotti ◽  
Irka Hajdas ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Numerical Model ◽  
Radiocarbon Dating ◽  
Overland Flow ◽  
Irrigation System ◽  
Archaeological Sites ◽  
New Approach ◽  
Sedimentary Deposits ◽  
New Evidence ◽  
Southern Flank

The oasis of Samarkand in the Middle Zeravshan Valley (modern Uzbekistan) was a major political and economic center in ancient western Central Asia. The chronology of its irrigation system was, until now, only constrained by the quality and quantity of archaeological findings and several different hypotheses have been proposed for it. We use a new approach combining archaeological surveying, radiocarbon dating, sedimentary analysis, and the numerical modeling of a flood event to offer new evidence for, and quantitative dating of, the development of irrigation system on the southern flank of the Middle Zeravshan Valley. We analyzed 13 bones and charcoals from 3 archaeological sites and obtained new 14C ages from Afrasiab (ancient Samarkand), a dwelling damaged by flooding in the 2nd century AD (site code: SAM-174) and the fortress of Kafir Kala. We established the origin of sedimentary deposits at the sites to infer the presence of the 2 most important canals of the southern flank: the Dargom and the Yanghiaryk. Finally, we show with a numerical model of overland flow that a natural flood was unlikely to have produced the damage observed at SAM-174. The combined results of the study indicate that the canals south of Samarkand existed, and were mainly developed, in the 2nd century AD and were not connected to the main feeding canal of Afrasiab at that time.

A nonlinear dynamic vibration model of a defective bearing: the importance of modelling the angle of the leading and trailing edges of a defect

2020 ◽  
pp. 147592172096395
Author(s):  
Francesco Larizza ◽  
Carl Q Howard ◽  
Steven Grainger ◽  
Wenyi Wang
Keyword(s):  
Numerical Model ◽  
Surface Defects ◽  
Vibration Response ◽  
Rolling Element Bearing ◽  
Analytical Models ◽  
Bearing Defect ◽  
Defect Profile ◽  
Vibration Model ◽  
Trailing Edges ◽  
Rolling Element

Rolling element bearings eventually become worn and fail by developing surface defects, such as spalls, dents and pits. Previous researchers have tested bearings with defects that have sharp [Formula: see text] rectangular edges that were used to develop analytical models of a defective bearing. These models have limitations that require smooth surfaces and constant curvature of the bearing components; as well as assuming the defect profile. A method has been created to capture the surface topography of a bearing defect. A numerical model has been developed for a rolling element bearing that uses the measured defect profile and removes the limitations of models by previous researchers that use analytical expressions for contact area and force. The predicted vibration response of a bearing with a defect that has sloped leading and trailing edges on the outer and inner raceway was compared with experimental results. It was found that the new numerical model was able to predict the vibration response of a defective bearing. The defect topographies and the developed model have been made publicly available.

scholarly journals Occurence of microplastics in the hyporheic zone of rivers

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
S. Frei ◽  
S. Piehl ◽  
B. S. Gilfedder ◽  
M. G. J. Löder ◽  
J. Krutzke ◽  
...  
Keyword(s):  
Drinking Water ◽  
Food Webs ◽  
Hyporheic Zone ◽  
River Sediments ◽  
Size Fraction ◽  
Dry Weight ◽  
Surface Flow ◽  
Hyporheic Exchange ◽  
Pore Scale ◽  
River Bank

Abstract Although recent studies indicate that fluvial systems can be accumulation areas for microplastics (MPs), the common perception still treats rivers and streams primarily as pure transport vectors for MPs. In this study we investigate the occurrence of MPs in a yet unnoticed but essential compartment of fluvial ecosystems - the hyporheic zone (HZ). Larger MP particles (500–5,000 µm) were detected using attenuated total reflectance (ATR) - Fourier-transform infrared (FTIR) spectroscopy. Our analysis of MPs (500–5,000 µm) in five freeze cores extracted for the Roter Main River sediments (Germany) showed that MPs were detectable down to a depth of 0.6 m below the streambed in low abundances (≪1 particle per kg dry weight). Additionally, one core was analyzed as an example for smaller MPs (20–500 µm) with focal plane array (FPA)- based µFTIR spectroscopy. Highest MP abundances (~30,000 particles per kg dry weight) were measured for pore scale particles (20–50 µm). The detected high abundances indicate that the HZ can be a significant accumulation area for pore scale MPs (20–50 µm), a size fraction that yet is not considered in literature. As the HZ is known as an important habitat for invertebrates representing the base of riverine food webs, aquatic food webs can potentially be threatened by the presence of MPs in the HZ. Hyporheic exchange is discussed as a potential mechanism leading to a transfer of pore scale MPs from surface flow into streambed sediments and as a potential vector for small MPs to enter the local aquifer. MPs in the HZ therefore may be a potential risk for drinking water supplies, particularly during drinking water production via river bank filtration.

scholarly journals Insight into the influence of local streambed heterogeneity on hyporheic-zone flow characteristics

2020 ◽  
Vol 28 (8) ◽  
pp. 2697-2712
Author(s):  
Robert Earon ◽  
Joakim Riml ◽  
Liwen Wu ◽  
Bo Olofsson
Keyword(s):  
Surface Water ◽  
Hydraulic Conductivity ◽  
Penetration Depth ◽  
Hyporheic Zone ◽  
Flow Characteristics ◽  
Time Lapse ◽  
Hyporheic Exchange ◽  
Tracer Injection ◽  
Hyporheic Flow ◽  
Exchange Processes

AbstractInteraction between surface water and groundwater plays a fundamental role in influencing aquatic chemistry, where hyporheic exchange processes, distribution of flow paths and residence times within the hyporheic zone will influence the transport of mass and energy in the surface-water/groundwater system. Geomorphological conditions greatly influence hyporheic exchange, and heterogeneities such as rocks and clay lenses will be a key factor for delineating the hyporheic zone. Electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) were used to investigate the streambed along a 6.3-m-long reach in order to characterise geological layering and distinct features which may influence parameters such as hydraulic conductivity. Time-lapse ERT measurements taken during a tracer injection demonstrated that geological features at the meter-scale played a determining role for the hyporheic flow field. The penetration depth of the tracer into the streambed sediment displayed a variable spatial pattern in areas where the presence of highly resistive anomalies was detected. In areas with more homogeneous sediments, the penetration depth was much more uniformly distributed than observed in more heterogeneous sections, demonstrating that ERT can play a vital role in identifying critical hydraulic features that may influence hyporheic exchange processes. Reciprocal ERT measurements linked variability and thus uncertainty in the modelled resistivity to the spatial locations, which also demonstrated larger variability in the tracer penetration depth, likely due to local heterogeneity in the hydraulic conductivity field.

scholarly journals Design of Self-Supported 3D Printed Parts for Fused Deposition Modeling

2016 ◽  
Author(s):  
Fabian Lischke ◽  
Andres Tovar
Keyword(s):  
Numerical Model ◽  
Fused Deposition Modeling ◽  
Beam Theory ◽  
Critical Factor ◽  
Acrylonitrile Butadiene Styrene ◽  
Material Model ◽  
Analytical Models ◽  
Element Analysis ◽  
Fused Deposition ◽  
3D Printed

One of the primary challenges faced in Additive Manufacturing (AM) is reducing the overall cost and printing time. A critical factor in cost and time reduction is post-processing of 3D printed (3DP) parts, of which removing support structures is one of the most time consuming steps. Support is needed to prevent the collapse of the part or certain areas under its own weight during the 3D printing process. Currently, the design of self-supported 3DP parts follows a set of empirical guide lines. A trial and error process is needed to produce high quality parts by Fused Depositing Modeling (FDM). The usage of chamfer angle with a max 45° angle form the horizontal for FDM is a common example. Inclined surfaces with a smaller angle are prone to defects, however no theoretical basis has been fully defined, therefore a numerical model is needed. The model can predict the problematic areas at a print, reducing the experimental prints and providing a higher number of usable parts. Physical-based models have not been established due to the generally unknown properties of the material during the AM process. With simulations it is possible to simulate the part at different temperatures with a variety of other parameters that have influence on the behavior of the model. In this research, analytic calculations and physical tests are carried out to determine the material properties of the thermoplastic polymer Acrylonitrile - Butadiene - Styrene (ABS) f or FDM at the time of extrusion. This means that the ABS is going to be extruded at 200°C to 245°C and is a viscous material during part construction. Using the results from the physical and analytical models, i.e., Timoshenko’s modified beam theory for micro-structures, a numerical material model is established to simulate the filament deformation once it is deposited onto the part. Experiments were also used to find the threshold for different geometric specifications, which could then be applied to the numerical model to improve the accuracy of the simulation. The result of the finite element analysis is compared to experiments to show the correlation between the prediction of deflection in simulation and the actual deflection measured in physical experiments. A case study was conducted using an application that optimizes topology of complex geometries. After modeling and simulating the optimized part, areas of defect and errors were determined in the simulation, then verified and and measured with actual 3D prints.

Modeling the Effect of Groundwater Abstraction on Wei River Riverine Ecological Flow Using the Coupled Model of Groundwater and Surfacewater

2012 ◽  
Vol 433-440 ◽  
pp. 1453-1457 ◽  
Author(s):  
Bo Zhang ◽  
Mei Hong ◽  
Zu Hao Zhou ◽  
Yang Wen Jia ◽  
Hui Li ◽  
...  
Keyword(s):  
Overland Flow ◽  
River Flow ◽  
Shallow Groundwater ◽  
Coupled Model ◽  
Wave Model ◽  
Coupling Model ◽  
Analysis Tool ◽  
Groundwater Abstraction ◽  
Coupled Calculation ◽  
Balance Analysis

In this study, the latest version of river boundary modular in MODFLOW, was employed in this watershed for the case study of coupled calculation between river and aquifer. Because of the complex interaction of groundwater and surface water in this area, the coupling model of SFR modular for river diffusive wave model and isochronal cell method for overland flow confluence model and numerical calculation of groundwater is coupled to simulate the runoff process of Weihe river. The model validation was aiming at river flow rate and groundwater field. The results show that 65% of the abstracted shallow groundwater comes from the river water and the reduced amount of river baseflow by the groundwater abstraction is 122 million m3 per year, which is also validated by a water balance analysis of river links. The 50% reduction of shallow groundwater abstraction may lead to a recover of 3 m of the lowest groundwater level. The study provides a sound analysis tool to the integrated water resources and ecology management in the region.

A three-dimensional model for analyzing the effects of salmon redds on hyporheic exchange and egg pocket habitat

2009 ◽  
Vol 66 (12) ◽  
pp. 2157-2173 ◽  
Author(s):  
Daniele Tonina ◽  
John M. Buffington
Keyword(s):  
Fluid Dynamics ◽  
Hydraulic Conductivity ◽  
Dissolved Oxygen ◽  
Oxygen Content ◽  
Three Dimensional ◽  
Hyporheic Exchange ◽  
Dimensional Model ◽  
Dynamics Model ◽  
Three Dimensional Model ◽  
Channel Hydraulics

A three-dimensional fluid dynamics model is developed to capture the spatial complexity of the effects of salmon redds on channel hydraulics, hyporheic exchange, and egg pocket habitat. We use the model to partition the relative influences of redd topography versus altered hydraulic conductivity (winnowing of fines during spawning) on egg pocket conditions for a simulated pool–riffle channel with a redd placed at the pool tail. Predictions show that altered hydraulic conductivity is the primary factor for enhancing hyporheic velocities and dissolved oxygen content within the egg pocket. Furthermore, the simulations indicate that redds induce hyporheic circulation that is nested within that caused by pool–riffle topography and that spawning-related changes in hyporheic velocities and dissolved oxygen content could create conditions suitable for incubation in locations that otherwise would be unfavorable (reinforcing the notion that salmonids actively modify their environment in ways that may be beneficial to their progeny).

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