scholarly journals New insights into particle transport in karst conduits using comparative tracer tests with natural sediments and solutes during low‐flow and high‐flow conditions

2022 ◽  
Author(s):  
Dominik Richter ◽  
Nadine Goeppert ◽  
Nico Goldscheider
Keyword(s):  
Particle Transport ◽  
Tracer Tests ◽  
High Flow ◽  
Low Flow ◽  
Flow Conditions

scholarly journals Soil microbial inoculation during flood events shapes headwater stream microbial communities and diversity

2021 ◽  
Author(s):  
Florian Caillon ◽  
Katharina Besemer ◽  
Peter Peduzzi ◽  
Jakob Schelker
Keyword(s):  
Microbial Diversity ◽  
Bacterial Diversity ◽  
Soil Water ◽  
Headwater Streams ◽  
High Flow ◽  
Low Flow ◽  
Flood Events ◽  
Flow Conditions ◽  
Soil Microbial ◽  
Microbial Inoculation

AbstractFlood events are now recognized as potentially important occasions for the transfer of soil microbes to stream ecosystems. Yet, little is known about these “dynamic pulses of microbial life” for stream bacterial community composition (BCC) and diversity. In this study, we explored the potential alteration of stream BCC by soil inoculation during high flow events in six pre-alpine first order streams and the larger Oberer Seebach. During 1 year, we compared variations of BCC in soil water, stream water and in benthic biofilms at different flow conditions (low to intermediate flows versus high flow). Bacterial diversity was lowest in biofilms, followed by soils and highest in headwater streams and the Oberer Seebach. In headwater streams, bacterial diversity was significantly higher during high flow, as compared to low flow (Shannon diversity: 7.6 versus 7.9 at low versus high flow, respectively, p < 0.001). Approximately 70% of the bacterial operational taxonomic units (OTUs) from streams and stream biofilms were the same as in soil water, while in the latter one third of the OTUs were specific to high flow conditions. These soil high-flow OTUs were also found in streams and biofilms at other times of the year. These results demonstrate the relevance of floods in generating short and reoccurring inoculation events for flowing waters. Moreover, they show that soil microbial inoculation during high flow enhances microbial diversity and shapes fluvial BCC even during low flow. Hence, soil microbial inoculation during floods could act as a previously overlooked driver of microbial diversity in headwater streams.

scholarly journals Remodeling of Resistance Arteries in Renal Failure: Effect of Endothelin Receptor Blockade

2001 ◽  
Vol 12 (10) ◽  
pp. 2040-2050 ◽  
Author(s):  
KERSTIN AMANN ◽  
GABRIEL MIL TENBERGER-MIL TENYI ◽  
AURELIA SIMONOVICIENE ◽  
ANDREAS KOCH ◽  
STEPHAN ORTH ◽  
...  
Keyword(s):  
Renal Failure ◽  
Blood Flow ◽  
High Flow ◽  
Mesenteric Arteries ◽  
Low Flow ◽  
Normal Flow ◽  
Flow Conditions ◽  
First Order ◽  
The Media ◽  
Intimal Thickness

Abstract. Remodeling of vessels is a known feature of renal failure, but it is unclear whether this represents an appropriate or inappropriate response to the known changes in blood flow, shear stress, and wall tension. To investigate remodeling in response to variations in blood flow, first-order mesenteric arteries were exposed to high- and low-flow conditions via the ligation of second-order branches, according to the technique described by Pour-ageaud and De Mey. The resulting changes in vessel geometric features, relative proportions of intima and media, submicroscopic structure, and immunostaining for proliferating cell nuclear antigen (PCNA), endothelin-1 (ET-1), and ETAreceptors were assessed in first-order mesenteric arteries under low-flow and high-flow conditions. Subtotally nephrectomized (SNX) animals were compared with sham-operated rats. Animals either were left untreated or were treated with the ETAreceptor antagonist (ET-RA) LU-135252, because of suggestions in the literature that ET is involved in vascular remodeling in uremia. A highly significant increase in intimal thickness was noted in low-flow arteries (4.21 ± 1.39 μm) of SNX animals, compared with normal-flow arteries (2.06 ± 0.61 μm), but this increase was not observed in sham-operated rats (1.38 ± 0.77 in low-flow arteriesversus2.40 ± 0.35 μm in normal-flow arteries). The increase in intimal thickness in low-flow arteries was abrogated by ET-RA. The medial thickness was increased in untreated SNX animals (19.5 ± 3.61 μm), compared with sham-operated rats, and this increase was also prevented by ET-RA. The medial thickness was not affected by low flow in either sham-operated or SNX animals. In parallel, the number of PCNA-positive intimal cells was higher in low-flow, but not high-flow, arteries of SNX rats, compared with sham-operated rats. No significant change was observed in sham-operated animals. In the media, the number of PCNA-positive cells was higher in untreated SNX animals than in sham-operated rats. The number was even more markedly increased in high-flow, but not low-flow, vessels. This increase was abrogated by ET-RA. It is concluded that, in uremic animals, the response of the intima to low flow and the response of the media to high flow are exaggerated. Both responses are apparently mediated by ET.

scholarly journals Hydrogeology of an alpine rockfall aquifer system and its role in flood attenuation and maintaining baseflow

2014 ◽  
Vol 11 (6) ◽  
pp. 6805-6841 ◽  
Author(s):  
U. Lauber ◽  
P. Kotyla ◽  
D. Morche ◽  
N. Goldscheider
Keyword(s):  
Tracer Tests ◽  
Low Flow ◽  
Flow Conditions ◽  
Flow Measurements ◽  
Aquifer System ◽  
Alpine Regions ◽  
Lag Times ◽  
Alpine Catchments ◽  
Underground Flow ◽  
Flood Attenuation

Abstract. The frequency and intensity of extreme hydrological events in alpine regions is projected to increase with climate change. The goal of this study was to better understand the functioning of aquifers composed of complex alluvial and rockfall deposits in alpine valleys and to quantify the role of these natural storage spaces in flood attenuation and baseflow maintenance. Geomorphological and hydrogeological mapping, tracer tests, and continuous flow measurements were conducted in the Reintal valley (German Alps), where runoff from a karst spring infiltrates into a series of postglacial alluvial/rockfall aquifers. During high-flow conditions, groundwater velocities of 30 m h−1 were determined along 500 m; hydrograph analyses revealed short lag times (5 h) between discharge peaks upstream and downstream from the aquifer series; the maximum discharge ratio downstream (22) and the peak recession coefficient (0.196 d−1) are low compared with other alpine catchments. During low-flow conditions, the underground flow path length increased to 2 km and groundwater velocities decreased to 13 m h−1. Downstream hydrographs revealed a delayed discharge response after 101 h and peaks dampened by a factor of 1.5. These results indicate that alluvial/rockfall aquifers might play an important role in the flow regime and attenuation of floods in alpine regions.

scholarly journals Longitudinal scattering coefficient obtained by hydroacoustic measurement and by conservative tracer

2021 ◽  
pp. 75-86
Author(s):  
Ana F. Nadal ◽  
José M. Díaz Lozada ◽  
Gonzalo P. Barbero Medina ◽  
Karen M. Moro ◽  
Mariana N. Melchiorre ◽  
...  
Keyword(s):  
Dispersion Coefficient ◽  
Flow Characteristics ◽  
Chemical Reactor ◽  
High Flow ◽  
Low Flow ◽  
Flow Conditions ◽  
Dry Period ◽  
Longitudinal Dispersion Coefficient ◽  
Transport Models ◽  
Conservative Tracer

The objective of the present work was to determine the value of the longitudinal dispersion coefficient (DL) of the Chicamtoltina stream (Alta Gracia) by means of two different techniques, in order to compare the values obtained. The first technique consisted of applying a developed formula that includes a detailed description of hydrodynamic parameters obtained by gauging with a hydroacoustic instrument, while the second technique consisted of injecting a conservative tracer, using the same approach as the non-ideal chemical reactor theory of flow with dispersion. This work was carried out at low flow conditions (dry period) and at high flow conditions (wet period). It was found that, either for high flow or low flow, the values of the dispersion coefficient obtained by both techniques have good agreement, fitting better in the dry period than in the wet period. Due to the fact that frequent gauging campaigns are carried out in this stream, it is concluded that with similar flow characteristics and morphology of the section, the gauging data can be used to determine the DL coefficient, in order to incorporate reliable data that can be applied to pollutant transport models.

Estimating river water-quality trends under different flow conditions

2021 ◽  
Author(s):  
Qian Zhang ◽  
James Webber ◽  
Douglas Moyer ◽  
Jeffrey Chanat
Keyword(s):  
Water Quality ◽  
River Water ◽  
Total Nitrogen ◽  
Nitrogen Concentration ◽  
High Flow ◽  
River Water Quality ◽  
Low Flow ◽  
Flow Conditions ◽  
Particulate Nitrogen ◽  
Water Quality Trends

&lt;p&gt;A number of statistical approaches have been developed to quantify the overall trend in river water quality, but most approaches are not intended for reporting separate trends for different flow conditions. We propose an approach called FN&lt;sub&gt;2Q&lt;/sub&gt;, which is an extension of the flow-normalization (FN) procedure of the well-established WRTDS (&amp;#8220;Weighted Regressions on Time, Discharge, and Season&amp;#8221;) method. The FN&lt;sub&gt;2Q&lt;/sub&gt;&amp;#160;approach provides a daily time series of low-flow and high-flow FN flux estimates that represent the lower and upper half of daily riverflow observations that occurred on each calendar day across the period of record. These daily estimates can be summarized into any time period of interest (e.g., monthly, seasonal, or annual) for quantifying trends. The proposed approach is illustrated with an application to a record of total nitrogen concentration (632 samples) collected between 1985 and 2018 from the South Fork Shenandoah River at Front Royal, Virginia (USA). Results show that the overall FN flux of total nitrogen has declined in the period of 1985&amp;#8211;2018, which is mainly attributable to FN flux decline in the low-flow class. Furthermore, the decline in the low-flow class was highly correlated with wastewater effluent loads, indicating that the upgrades of treatment technology at wastewater treatment facilities have likely led to water-quality improvement under low-flow conditions. The high-flow FN flux showed a spike around 2007, which was likely caused by increased delivery of particulate nitrogen associated with sediment transport. The case study demonstrates the utility of the FN&lt;sub&gt;2Q&lt;/sub&gt;&amp;#160;approach toward not only characterizing the changes in river water quality but also guiding the direction of additional analysis for capturing the underlying drivers. The FN&lt;sub&gt;2Q&lt;/sub&gt; approach (and the published code) can easily be applied to widely available river monitoring records to quantify water-quality trends under different flow conditions to enhance understanding of river water-quality dynamics. &lt;span&gt;(Journal article: https://doi.org/10.1016/j.scitotenv.2020.143562; R code and data release: https://doi.org/10.5066/P9LBJEY1).&lt;/span&gt;&lt;/p&gt;

Characteristics of sediments in a newly constructed reservoir in Japan

2006 ◽  
Vol 53 (2) ◽  
pp. 73-78 ◽  
Author(s):  
Y. Sakurai ◽  
S. Haruta
Keyword(s):  
High Flow ◽  
Low Flow ◽  
Particulate Phosphorus ◽  
Formation Mechanisms ◽  
Flow Conditions ◽  
Discharge Rates ◽  
Main River ◽  
Sediment Formation ◽  
Specific Discharge ◽  
Land Surfaces

The sediment formation mechanisms of a newly constructed reservoir in Ehime, Japan were evaluated by characterizing the soil particles (SP) and particulate phosphorus (PP) in the runoff and reservoir sediments. The SP and PP loads from the runoffs of the main river in the watershed considerably increased, when the specific discharge rates were over 300 l/s/km2 (high flow conditions). When the specific discharge rates exceeded over 300 l/s/km2, 19% of the watershed generated over 80% of the SP and PP loads. When the specific discharge rates were under 300 l/s/km2 (low flow conditions), the contributions of the previously mentioned 19% area to the SP and PP loads were smaller. Significant amounts of smectite were found in the sediments in the reservoir and in the soil samples obtained at the forest exposed area in this 19% area while it was negligible in citrus orchards and paddy fields that constituted the remaining land surfaces. The forest area exposed by recent landslides was significant for the SP and PP in the reservoir. Judging from the outcomes, land use information alone may not be sufficient to detect critical sources of SP and PP in the runoffs and reservoirs. To identify and confirm crucial areas for the SP and PP in the runoffs, the investigations should be conducted under high flow conditions and the composition of clay minerals in the sediments should be checked against the clay mineral distributions of soils in the watershed.

scholarly journals Hydrogeology of an Alpine rockfall aquifer system and its role in flood attenuation and maintaining baseflow

2014 ◽  
Vol 18 (11) ◽  
pp. 4437-4452 ◽  
Author(s):  
U. Lauber ◽  
P. Kotyla ◽  
D. Morche ◽  
N. Goldscheider
Keyword(s):  
Tracer Tests ◽  
Low Flow ◽  
Flow Conditions ◽  
Flow Measurements ◽  
Aquifer System ◽  
Alpine Regions ◽  
Lag Times ◽  
Alpine Catchments ◽  
Underground Flow ◽  
Flood Attenuation

Abstract. The frequency and intensity of extreme hydrological events in Alpine regions is projected to increase with climate change. The goal of this study is to better understand the functioning of aquifers composed of complex alluvial and rockfall deposits in Alpine valleys and to quantify the role of these natural storage spaces in flood attenuation and baseflow maintenance. Geomorphological and hydrogeological mapping, tracer tests, and continuous flow measurements were conducted in the Reintal (German Alps), where runoff from a karst spring infiltrates a series of postglacial alluvial/rockfall aquifers. During high-flow conditions, groundwater velocities of 30 m h−1 were determined along 500 m; hydrograph analyses revealed short lag times (5 h) between discharge peaks upstream and downstream from the aquifer series; the maximum discharge ratio downstream (22) and the peak recession coefficient (0.196 d−1) are low compared with other Alpine catchments. During low-flow conditions, the underground flow path length increased to 2 km and groundwater velocities decreased to 13 m h−1. Downstream hydrographs revealed a delayed discharge response after 101 h and peaks damped by a factor of 1.5. These results indicate that alluvial/rockfall aquifers might play an important role in the flow regime and attenuation of floods in Alpine regions.

scholarly journals Meltwater flow through a rapidly deglaciating glacier and foreland catchment system: Virkisjökull, SE Iceland

2017 ◽  
Vol 48 (6) ◽  
pp. 1666-1681 ◽  
Author(s):  
Verity Flett ◽  
Louise Maurice ◽  
Andrew Finlayson ◽  
Andrew R. Black ◽  
Alan M. MacDonald ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Tracer Tests ◽  
Tracer Test ◽  
Low Flow ◽  
Flow Conditions ◽  
Flow Measurements ◽  
Tracer Testing ◽  
Flow Through ◽  
Conduit System ◽  
Ground Penetrating

Abstract Virkisjökull is a rapidly retreating glacier in south-east Iceland. A proglacial lake has formed in the last ten years underlain by buried ice. In this study we estimate water velocities through the glacier, proglacial foreland and proglacial river using tracer tests and continuous meltwater flow measurements. Tracer testing from a glacial moulin to the glacier outlet in September 2013 demonstrated a rapid velocity of 0.58 m s−1. This was comparable to the velocity within the proglacial river, also estimated from tracer testing. A subsequent tracer test from the same glacial moulin under low flow conditions in May 2014 demonstrated a slower velocity of 0.07 m s−1. The glacier outlet river sinks back into the buried ice, and a tracer test from this sink point through the proglacial foreland to the meltwater river beyond the lake indicated a velocity of 0.03 m s−1, suggesting that an ice conduit system within the buried ice is transferring water rapidly beneath the lake. Ground penetrating radar profiles confirm the presence of this buried conduit system. This study provides an example of rapid deglaciation being associated with extensive conduit systems that enable rapid meltwater transfer from glaciers through the proglacial area to meltwater rivers.

Turbulence Numerical Simulation and Particle Track Analysis of Slurry Pump Impeller

2013 ◽  
Vol 655-657 ◽  
pp. 336-339
Author(s):  
Heng Zhang ◽  
Yan Chao Yin
Keyword(s):  
Cavitation Erosion ◽  
Fluid Phase ◽  
High Flow ◽  
Low Flow ◽  
Flow Conditions ◽  
Lagrange Method ◽  
Pump Impeller ◽  
Wear Performance ◽  
Pump Design ◽  
Track Analysis

In order to improve the pump wear performance and optimize pump design, the Euler-Lagrange approach is chosen to simulate the flow in the impeller. The fluid phase is treated as a continuum by solving the N-S equations, while the dispersed phase is solved by using Lagrange Method through the calculated flow field. The results show that the reflex appears in the blade inlet of pressure sides in high flow conditions, but appears in the blade inlet of suction sides in low flow conditions, which possibly induce the cavitation erosion. In low flow conditions, reflex and eddies appear in the blade outlet of both the pressure sides and the suction sides, and the reflex areas even extend to the middle of blades. In the range of simulated conditions, the suction sides don’t collide with particles. The pressure sides collide with particles in the form of continuous impact in low flow conditions but scratch in high flow conditions.

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