scholarly journals Flow characteristics of intermittent rivers in Slovakia

2018 ◽  
Vol 50 (3) ◽  
pp. 215-227 ◽  
Author(s):  
Agnieszka Rutkowska ◽  
Silvia Kohnová ◽  
Kazimierz Banasik ◽  
Jan Szolgay
Keyword(s):  
Flow Characteristics ◽  
Hydrological Regime ◽  
Climatic Changes ◽  
Circular Statistics ◽  
Ephemeral Streams ◽  
Entire Region ◽  
Intermittent Rivers ◽  
Increasing Temperature ◽  
The Cost ◽  
Water Supply Reservoirs

Abstract Flow characteristics of intermittent rivers in Slovakia. Intermittent rivers are rivers that cease to fl ow, i.e. temporary, ephemeral, seasonal, and episodic rivers. Analysis of hydrological regime of such rivers is pivotal in assessment of water resources because changes in fl ow characteristics of such rivers may affect neighboring catchments or the entire region through changes in water supply reservoirs such as lakes, wetlands and mosses. Recently, an increasing number of intermittent rivers and ephemeral streams (IRES) and an elongation of the zero- -fl ow events has been observed in Europe due to climatic changes and anthropogenic influence. Intermittent rives in Slovakia were studied in the paper using statistical methods. The characteristics of the zero-fl ow period, of duration of the longest annual zero-fl ow event and of timing of such events were derived. The circular statistics were helpful in recognition of the dates of occurrence of such events. The comparative analysis between catchments was performed. The variability in precipitation and evapotranspiration and the increasing temperature were identified as the possible drivers of the fl ow intermittence in these catchments. The research was performed within the COST Action SMIRES (Science and Management of Intermittent Rivers & Ephemeral Streams).

Hydrological regime and sediment transport in two Mediterranean intermittent rivers and ephemeral streams (IRESs)

2020 ◽  
Author(s):  
Giovanni Francesco Ricci ◽  
Josep Fortesa ◽  
Julián García-Comendador ◽  
Francesco Gentile ◽  
Joan Estrany ◽  
...  
Keyword(s):  
Flow Regime ◽  
Suspended Sediment ◽  
Management Practices ◽  
Hydrological Regime ◽  
Hysteretic Behavior ◽  
Ephemeral Streams ◽  
Runoff Coefficient ◽  
Event Scale ◽  
Intermittent Rivers ◽  
Infiltration Excess

<p>In intermittent rivers and ephemeral streams (IRES), the hydrological regime is the primary driving force controlling the sediment transfer from the upland to the lowland catchment compartment, ergo the river geomorphology. The general objective of this study is to investigate the processes and the relationships between flow regime and suspended sediment (SS) transport in two IRESs with a different degree of intermittency, the Búger River (Spain) and the Carapelle River (Italy). The specific objectives are to (i) identify the drivers of SS transport, (ii) analyse and quantify the temporal variability of the SS transport in response to the hydrological regime. High-resolution data of streamflow and SS concentration (SSC) were used in this analysis and a set of hydrological indicators were computed to characterize and classify the flow regime.</p><p>In the Búger River, the high degree of intermittency and the low runoff coefficient were mainly due to the presence of carbonate lithology in headwaters and the specific SS yield (SSY: 0.5-46 t km<sup>-2</sup> yr<sup>-1</sup>) was strongly influenced by the flow regime. In the Carapelle River, the high values of the annual runoff coefficient (14-35%) and SSY (89-745 t km<sup>-2</sup> yr<sup>-1</sup>) were related to clay and limestone lithology. Most of the annual SSY was transported during floods. In the Búger River, SSY and maximum SSC (SSCmax) were correlated with the runoff, peak discharge, and antecedent rainfall. In the Carapelle River, SSY and SSCmax were correlated to the amount and intensity of rainfall. The catchment size played an important role in the hysteretic behavior since it had an influence on the spatial rainfall and sediment sources distribution. Búger River showed predominant clockwise loops as SS sources were close to the outlet. In the Carapelle River basin, clockwise and counter-clockwise were generated as the larger agricultural area promoted a huge sediment availability.</p><p>Lithology and geological characteristics resulted in the most relevant drivers controlling the hydrological regime and river type classification, meanwhile, rainfall was a less relevant factor. Land use and management practices were also relevant factors in SSY, determining the availability of suspended sediment material. At the event scale, a non-linearity in the rainfall-runoff relationship was found for both catchments, as runoff response can be due to different processes (i.e., saturation or infiltration excess).</p><p>This work was supported by the research project CGL2017-88200-R “Functional hydrological and sediment connectivity at Mediterranean catchments: global change scenarios –MEDhyCON2” funded by the Spanish Ministry of Science, Innovation and Universities, the Spanish Agency of Research (AEI), the European Regional Development Funds (ERDF),  the project “Soil Erosion in Apulia: Monitoring, Modelling and Control Strategies” performed within University of Bari and funded by the Apulia Basin Authority and the COST Action CA15113 Science and Management of Intermittent Rivers and Ephemeral Streams (SMIRES).</p>

scholarly journals Hydrological, Environmental and Taxonomical Heterogeneity during the Transition from Drying to Flowing Conditions in a Mediterranean Intermittent River

Biology ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 316
Author(s):  
Andy Banegas-Medina ◽  
Isis-Yelena Montes ◽  
Ourania Tzoraki ◽  
Luc Brendonck ◽  
Tom Pinceel ◽  
...  
Keyword(s):  
Ecosystem Services ◽  
Base Flow ◽  
Ephemeral Streams ◽  
Biogeochemical Processes ◽  
Flow Conditions ◽  
Intermittent Rivers ◽  
Terrestrial Biodiversity ◽  
Turn Over ◽  
Zero Flow ◽  
Intermittent River

Intermittent rivers and ephemeral streams (IRES) are increasingly studied because of their often-unique aquatic and terrestrial biodiversity, biogeochemical processes and associated ecosystem services. This study is the first to examine the hydrological, physicochemical and taxonomic variability during the dry-wet transition of an intermittent river in the Chilean Mediterranean Zone. Based on 30-years of river monitoring data and the TREHS tool, the hydrology of the river was characterised. Overall, the river shows a significant reduction in streamflow (−0.031 m3/s per year) and a substantial increase of zero flow days (+3.5 days per year). During the transition of hydrological states, variations were observed in the environmental conditions and invertebrate communities. During the drying phase, abundance, richness, and diversity were highest, while species turn-over was highest during base flow conditions. The disconnected pools and the flow resumption phases were characterised by high proportions of lentic taxa and non-insects, such as the endemic species of bivalves, gastropods, and crustaceans, highlighting the relevance of disconnected pools as refuges. Future climatic change scenarios are expected to impact further the hydrology of IRES, which could result in the loss of biodiversity. Biomonitoring and conservation programmes should acknowledge these important ecosystems.

scholarly journals Unlocking our understanding of intermittent rivers and ephemeral streams with genomic tools

2021 ◽  
Author(s):  
Rosetta C Blackman ◽  
Florian Altermatt ◽  
Arnaud Foulquier ◽  
Tristan Lefébure ◽  
Maïlys Gauthier ◽  
...  
Keyword(s):  
Ephemeral Streams ◽  
Intermittent Rivers ◽  
Genomic Tools

Characterisation of Static Strip Seal Flow

2007 ◽  
Author(s):  
Arash Farahani ◽  
Peter Childs
Keyword(s):  
Gas Flow ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Main Stream ◽  
Cfd Modelling ◽  
Height Range ◽  
And Performance ◽  
Nozzle Guide ◽  
The Cost ◽  
Cooling Air

Strip seals are used in gas turbine engines between two static elements or between components which do not move relative to each other, such as Nozzle Guide Vanes (NGVs). The key role of a strip seal between NGV segments is sealing between the flow through the main stream annulus and the internal air system, a further purpose is to limit the inter-segmental movements. In general the shape of the strip seal is a rectangular strip that fits into two slots in adjacent components. The minimum clearance required for static strip seals must be found by accounting for thermal expansion, misalignment, and application, to allow correct fitment of the strip seals. Any increase in leakage raises the cost due to an increase in the cooling air use, which is linked to specific fuel consumption, and it can also alter gas flow paths and performance. The narrow path within the seal assembly, especially the height has the most significant affect on leakage. The height range of the narrow path studied in this paper is 0.01–0.06 mm. The behaviour of the flow passing through the narrow path has been studied using CFD modelling and measurements in a bespoke rig. The CFD and experimental results show that normalized leakage flow increases with pressure ratio before reaching a maximum. The main aim of this paper is to provide new experimental data to verify the CFD modelling for static strip seals. The typical flow characteristics validated by CFD modelling and experiments can be used to predict the flow behaviour for future static strip seal designs.

scholarly journals Science and Management of Intermittent Rivers and Ephemeral Streams (SMIRES)

2017 ◽  
Vol 3 ◽  
pp. e21774 ◽  
Author(s):  
Thibault Datry ◽  
Gabriel Singer ◽  
Eric Sauquet ◽  
Dídac Jorda-Capdevila ◽  
Daniel Von Schiller ◽  
...  
Keyword(s):  
Ecological Status ◽  
Global Scale ◽  
Research Network ◽  
River Networks ◽  
Ephemeral Streams ◽  
Catchment Scale ◽  
Water Demands ◽  
Raising Awareness ◽  
Intermittent Rivers ◽  
Working Groups

More than half of the global river network is composed of intermittent rivers and ephemeral streams (IRES), which are expanding in response to climate change and increasing water demands. After years of obscurity, the science of IRES has bloomed recently and it is being recognised that IRES support a unique and high biodiversity, provide essential ecosystem services and are functionally part of river networks and groundwater systems. However, they still lack protective and adequate management, thereby jeopardizing water resources at the global scale. This Action brings together hydrologists, biogeochemists, ecologists, modellers, environmental economists, social researchers and stakeholders from 14 different countries to develop a research network for synthesising the fragmented, recent knowledge on IRES, improving our understanding of IRES and translating this into a science-based, sustainable management of river networks. Deliverables will be provided through i) research workshops synthesising and addressing key challenges in IRES science, supporting research exchange and educating young researchers, and ii) researcher-stakeholder workshops translating improved knowledge into tangible tools and guidelines for protecting IRES and raising awareness of their importance and value in societal and decision-maker spheres. This Action is organized within six Working Groups to address: (i) the occurrence, distribution and hydrological trends of IRES; (ii) the effects of flow alterations on IRES functions and services; (iii) the interaction of aquatic and terrestrial biogeochemical processes at catchment scale; (iv) the biomonitoring of the ecological status of IRES; (v) synergies in IRES research at the European scale, data assemblage and sharing; (vi) IRES management and advocacy training.

scholarly journals Simulating rewetting events in intermittent rivers and ephemeral streams: A global analysis of leached nutrients and organic matter

2019 ◽  
Vol 25 (5) ◽  
pp. 1591-1611 ◽  
Author(s):  
Oleksandra Shumilova ◽  
Dominik Zak ◽  
Thibault Datry ◽  
Daniel Schiller ◽  
Roland Corti ◽  
...  
Keyword(s):  
Organic Matter ◽  
Global Analysis ◽  
Ephemeral Streams ◽  
Intermittent Rivers

scholarly journals Improvement of anisotropic porosity models with a merging technique

2018 ◽  
Vol 40 ◽  
pp. 06023
Author(s):  
Martin Bruwier ◽  
Pierre Archambeau ◽  
Sébastien Erpicum ◽  
Michel Pirotton ◽  
Benjamin Dewals
Keyword(s):  
Shallow Water ◽  
Flow Characteristics ◽  
Threshold Value ◽  
Computational Grid ◽  
Computational Time ◽  
Time Step ◽  
Shallow Water Models ◽  
The Cost ◽  
The Impact ◽  
Porosity Model

Anisotropic porosity shallow-water models are used to take into account detailed topographic information through porosity parameters multiplying the various terms of the shallow-water equations. A storage porosity is assigned to each cell to reflect the void fraction in the cell and a conveyance porosity is used at each edge to reproduce the impact of subgrid obstacles on the flux terms. To guaranty the numerical stability, the time step depends on the value of the porosity parameters. This may hamper severely the computational efficiency in the presence of cells with low values of storage porosity. Cartesian grids are particularly sensitive to such a case since the meshing stems directly from the choice of the grid size. In this paper, this problem is addressed by using an original merging technique consisting in merging cells with a storage porosity lower than a threshold value with neighbouring cells. The model was tested for modelling a prismatic channel with different orientations between the Cartesian computational grid and the channel direction. The results show that the standard anisotropic porosity model (without merging) improves the reproduction of the flow characteristics; but at the cost of a significantly higher computational time. In contrast, the computational time is drastically reduced and the accuracy preserved when the merging technique is used with the porosity model.

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